NZ763583B2 - Methods, kits and apparatus for expanding a population of cells - Google Patents

Abstract

The present invention relates to in vitro-methods of expanding a population of cells such as lymphocytes, comprising contacting a sample comprising a population of cells with a multimerization reagent. The multimerization reagent has reversibly immobilized thereon (bound thereto) a first agent that provides a primary activation signal to the cells and optionally, a second agent that provides a co-stimulatory signal. The invention also provides multimerization reagents, kits, arrangements and an apparatus for expanding cells. provides a primary activation signal to the cells and optionally, a second agent that provides a co-stimulatory signal. The invention also provides multimerization reagents, kits, arrangements and an apparatus for expanding cells.

Description

METHODS, KITS AND APPARATUS FOR EXPANDING A POPULATION OF CELLS CROSS-REFERENCE TO RELATED ATIONS The present invention claims the benefit of priority to US provisional patent application 61/980,506 "Methods, Kits And Apparatus For Expanding A Population Of Cells " filed with the US Patent and Trademark Office on 16 April 2014, the contents of which is hereby incorporated by reference in its entirety for all purposes.

FIELD OF THE ION The present invention relates to the expansion feration) of a population of cells such as a population of lymphocytes. The invention in general provides novel methods and reagents for the expansion (proliferation) of cell populations that require binding of a receptor binding le (such as a first agent as bed herein) to a receptor molecule on the surface of the cells, thereby providing a primary activation signal to the cells. The invention employs a erization reagent that has lized thereon (bound thereto) a first agent that provides a primary activation signal to the cells. This primary tion signal may as such be sufficient to activate the cells to expand/proliferate. This first agent can either be bound reversibly or also irreversibly to the multimerization reagent. The multimerization reagent may have immobilized thereon (bound thereto) also a second agent that stimulates an accessory le on the surface of the cells. The second agent, when binding to the accessory molecule on the surface on the surface of the cells, may thereby stimulate the activated cells to expand. Also this second agent can either be bound reversibly or also irreversibly to the multimerization reagent. The multimerization agent may either be immobilized on a solid support or soluble. In one aspect, the method disclosed herein is a serial expansion of a population of cells in which a complete population of lymphocytes is stimulated/expanded, the reagents necessary for the expansion are then removed by chromatography on a suitable nary phase and the expanded/stimulated cells are optionally transfected with e.g. a T cell receptor or a chimeric antigen receptor (CAR) and subjected to a second stimulation expansion with a different stimulatory molecule that binds to the uced T cell receptor or the chimeric n receptor. The invention also relates to an apparatus for the expansion of the selected cell population.

BACKGROUND OF THE INVENTION The development of techniques for propagating T cell populations in vitro has been crucial to many of the advances in the understanding of T cell recognition of antigen and T cell activation. The development of culture methods for the generation of human antigen- specific T cell clones has been useful in g antigens expressed by pathogens and tumors that are recognized by T cells to establish methods of immunotherapy to treat a variety of human diseases. Antigen—specific T cells can be expanded in vitro for use in adoptive cellular immunotherapy or cancer therapy in which infusions of such T cells have been shown to have anti-tumor reactivity in a tumor-bearing host. In addition, ve immunotherapy has also been used to treat viral infections in compromised individuals.

A method of expanding human T cells in vitro in the absence of exogenous growth factor and ory cells that has been established in the recent years is described in US Patent 6,352,694 B1 and European Patent EP 0 700 430 B1. Disclosed in these patents is an in vitro method for ng a population of T cells to proliferate. The method comprises contacting a population of T cells with a solid phase surface having directly immobilized thereon: (a) a first agent which provides a primary activation signal to the T cells, thereby activating the T cells; and (b) a second agent which stimulates an accessory molecule on the surface of the T cells, thereby ating the activated T cells. The binding of the first agent and the second agent to the T cells induces the T cells to proliferate/to expand. The red first agent described in US Patent 6,352,694 B1 and European Patent EP 0 700 430 B1 is a onal anti-CD3 antibody which binds to the TCR/CD3 (TCR = T Cell Receptor) complex and thereby ates the TCR/CD3 x-associated signal in the T cells. The preferred second agent according to these two patents is a monoclonal anti—CD28 antibody which binds the accessory le CD28 that is present on T cells. Binding of this second agent to the CD28 ory molecule provides the necessary co-stimulus that is necessary for expansion/proliferation of activated T cells. Meanwhile, Dynabeads® CD3/CD28 (Invitrogen) are commercially available for T cell expansion. Dynabeads® CD3/CD28 CTSTM are uniform, 4.5 um superparamagnetic, sterile, non-pyrogenic polystyrene beads coated with a mixture of y purified monoclonal antibodies against the CD3 and CD28 cell surface molecules on human T cells.

However, such magnetic beads are, for example, difficult to integrate into a method to expand cells under conditions required for clinical trials or therapeutic purposes since it has to be made sure that these magnetic beads are tely removed before administering the expanded T cells to a patient. Thus, the present invention aims to provide an alternative method for expanding cell populations such as tory T cells or central memory T-cells for research, diagnostic and especially therapeutic purposes. Ideally, this new method should also be compatible with integration into an automatized process which can be used for rapid and easy expansion of the desired cells population for therapeutic ations.

This object is solved by the subject matter of the independent , inter alia the methods, kits, arrangements and apparatuses as recited in the independent claims.

SUMMARY OF THE INVENTION The present invention provides s, kits, arrangements, and apparatus for the in vitro expansion of a desired cell population, having a receptor molecule on its surface which can provide upon binding of a le agent a primary tion signal to the population of cells and thereby activating the population of cells for expansion (proliferation). Thus, the methods of the invention are also used for inducing a tion of cells to proliferate.

According to a first aspect, the invention provides an in vitro-method of expanding a population of cells, comprising contacting a sample comprising the population of cells with a multimerization reagent, wherein the multimerization reagent has reversibly immobilized thereon (bound thereto) a first agent that provides a primary activation signal to the cells; wherein the multimerisation reagent comprises at least one g site 21 for the reversible binding of the first agent, wherein the first agent comprises at least one binding partner Cl, wherein the binding partner Cl is able of reversibly binding to the g site 21 of the multimerization reagent, wherein the first agent is bound to the erization reagent via the reversible bond formed between the binding partner Cl and the binding site Z], and wherein the first agent binds to a receptor molecule on the surface of the cells, thereby providing a y activation signal to the cells and thereby activating the cells.

According to a second aspect the invention provides an in vitro-method of expanding a population of cells, comprising contacting a sample sing the population of cells with a multimerization reagent, wherein the multimerization reagent is in a soluble form and has immobilized thereon (bound o) a first agent that provides a y activation signal to the cells; wherein the multimerisation reagent comprises at least one binding site Z] for the binding ofthe first agent, wherein the first agent comprises at least one binding partner Cl, wherein the binding partner C1 is able of binding to the binding site Z1 of the multimerization reagent, wherein the first agent is bound to the multimerization reagent Via the bond formed between the binding partner C1 and the binding site Z1, and wherein the first agent binds to a receptor molecule on the surface of the cells, thereby ing a y activation signal to the cells and thereby activating the cells.

According to a third aspect the invention provides a reagent kit for expanding a tion of cells, the kit comprising (i) a multimerization reagent, wherein the multimerisation reagent comprises at least one g site Z for the ible binding of a first agent, (ii) a first agent that binds to a receptor molecule on the surface of the cells, thereby ing a primary activation signal to the cells and thereby activating the cells, wherein the first agent comprises at least one binding r Cl, wherein the binding partner Cl is able of reversibly binding to a binding site Z1 of the multimerization reagent, wherein the first agent is bound to the multimerization reagent via the reversible bond formed between the g partner Cl and the binding site Z1, and (iii) a second agent that stimulates an accessory molecule on the surface of the cells, wherein the second agent comprises a binding partner C2, wherein the binding partner C2 is able of reversibly binding to a binding site Z2 of the multimerization reagent, wherein the second agent is bound to the multimerization reagent via the bond formed between the binding partner C2 and the g site Z2, wherein the second agent binds to the accessory molecule on the surface on the surface ofthe cells, thereby stimulating the activated cells.

According to a fourth aspect the invention provides a reagent kit for expanding a tion of cells, the kit sing (i) a multimerization reagent, wherein the multimerisation reagent is in soluble form and comprises at least one binding site Z for the reversible binding of a first agent, (ii) a first agent that binds to a receptor molecule on the surface of the cells, y providing a primary activation signal to the cells and y activating the cells, n the first agent comprises at least one binding partner Cl, wherein the binding partner Cl is able of binding to a binding site Zl of the multimerization reagent, wherein the first agent is bound to the multimerization t via the reversible bond formed n the binding partner C1 and the binding site Z1.

According to a fifth aspect the invention provides an in vitro-method of serially expanding a population of lymphocytes, wherein the population of lymphocytes ses T cells, the method comprising contacting a sample comprising the T cell comprising population of lymphocytes with a multimerization reagent, wherein the multimerization reagent is in a e form and has reversibly immobilized thereon (i) a first agent that es a primary activation signal to the T cells and (ii) a second agent which stimulates an accessory molecule on the surface of the T cells, wherein the multimerisation reagent ses at least one binding site Z] for the reversible binding of the first agent, wherein the first agent comprises at least one binding partner Cl, wherein the binding partner Cl is able of reversibly binding to the binding site Z] of the multimerization reagent, wherein the first agent is bound to the multimerization t via the reversible bond formed between the binding partner Cl and the binding site Z1, wherein the erisation reagent comprises at least one binding site Z2 for the reversible binding of the second agent, wherein the second agent comprises at least one binding partner C2, wherein the binding partner C2 is able of reversibly binding to the binding site Z2 of the multimerization reagent, wherein the first agent is bound to the multimerization reagent via the reversible bond formed n the binding partner C2 and the binding site Z2, wherein the first agent binds to a receptor molecule on the surface of the T cells, thereby providing a primary activation signal to the cells and thereby activating the T cells, wherein the second agent binds to the accessory molecule on the surface of the T cells, thereby stimulating the activated cells, the first agent and the second agent thereby together inducing the T cells to expand.

According to a sixth aspect the invention provides an arrangement of a bioreactor and a stationary phase for chromatography, wherein the bioreactor is suitable for the expansion of cells, wherein the stationary phase is suitable for cell tion and removal of reagents, the stationary phase being a gel filtration matrix and/or affinity chromatography , wherein the gel filtration and/or affinity chromatography matrix comprises an y t, wherein the affinity reagent comprises a binding site Z1 specifically binding to a binding partner C1 comprised in a first agent and/or the affinity t comprises a binding site Z2 cally binding to a binding partner C2 sed in a second agent, thereby being suitable of immobilizing on the stationary phase the first agent and/or the second agent, the first binding partner Cl and/or the free second binding partner C2, n the ctor and the stationary phase are fluidly connected. id="p-14" id="p-14" id="p-14" id="p-14" id="p-14"

[0014] According to a seventh aspect the invention provides an apparatus for purification and expansion of a population of cells, the apparatus comprising at least one arrangement of a bioreactor and a stationary phase for chromatography according to the sixth aspect.

According to an eight aspect, the invention provides a multimerization reagent capable of expanding a population of cells, wherein the multimerisation reagent is in soluble form and comprises at least one binding site Z] for the reversible g of a first agent that provides a primary activation signal to the cells, wherein the multimerization reagent has reversibly immobilized thereon (bound thereto) said first agent that provides a primary activation signal to the cells; n the first agent comprises at least one binding partner Cl, wherein the binding partner C1 is able of reversibly binding to the at least one binding site Z1 of the multimerization reagent, wherein the first agent is bound to the multimerization reagent Via the ible bond formed between the binding partner C1 and the binding site 21, According to a ninth aspect, the invention provides a composition capable of expanding a population of cells, the composition comprising (i) a first multimerization reagent, wherein the first multimerisation reagent is in soluble form and comprises at least one binding site Z1 for the ible binding of a first agent that es a primary activation signal to the cells, wherein the first multimerization reagent has reversibly immobilized thereon (bound thereto) said first agent that provides a primary activation signal to the cells; wherein the first agent comprises at least one binding partner C1, wherein the binding partner Cl is able of ibly binding to the at least one binding site Zl of the multimerization reagent, wherein the first agent is bound to the erization reagent via the reversible bond formed between the binding r Cl and the binding site Z1, (ii) a second multimerization reagent, wherein the second multimerization reagent is in e form and comprises at least one binding site Z2 for the reversible binding of a second agent that stimulates an accessory molecule on the surface of the cells, wherein the multimerization reagent has reversibly immobilized thereon (bound thereto) said second agent that stimulates an accessory molecule on the surface of the cells, wherein the second agent comprises a g partner C2, wherein the binding partner C2 is able of binding to the at least one binding site Z2 of the erization reagent, wherein the second agent is bound to the multimerization t via the bond formed between the binding partner C2 and the binding site Z2.

DESCRIPTION OF THE DRAWINGS The invention will be better understood with reference to the detailed description when considered in conjunction with the miting examples and the accompanying drawings. The figures illustrate embodiments of methods of the invention. t wishing to be bound by theory, the figures include conclusions with regard to the underlying expansion ism. The conclusions are given for illustrative purposes only and merely serve in allowing a visualization of the expansion method is able on a molecular level.

Figure 1 depicts an embodiment of an in vitro—method of expanding of expanding a population of cells that has a cell surface receptor the binding of which by a first agent can provide an tion signal for the cells to expand.

As shown in Fig. 1a a sample that comprises the population of cells (2) that carry a surface receptor le (30) is contacted with a multimerization reagent (4). The population of cells (2) is in mixture with other cell populations (22) that lack the surface receptor molecule (30). The multimerization t (4) has reversibly immobilized thereon (bound thereto) a first agent (6) that provides a primary activation signal to the cells. The multimerization t (4) comprises at least one binding site Z1 (42) for the reversible binding of the first agent (6) and the first agent (6) comprises at least one binding partner Cl (6a), wherein the binding partner C1 (6a) is able of reversibly binding to the binding site Z1 (44) of the multimerization reagent. Thus, for immobilization, the first agent (6) is bound to the erization reagent (4) Via the reversible bond formed between the binding partner Cl (6a) and the binding site Z1 (42). In the example shown in Fig. l the multimerization reagent (4) has a second binding site Z2 (44) which is not used in this example. The multimerization reagent (4) is itself immobilized on a solid support (10) such as a magnetic bead, a polymeric bead of a surface of a cell culture plate or reactor. The population of cells (2) can, for example be, a lymphocyte cell tion such as a population of B cells that can be activated via the CD40 receptor (see, for example, Carpenter et al, Journal of Translational Medicine 2009, 7:93 "Activation of human B cells by the agonist CD40 antibody CP-870,893 and augmentation with simultaneous toll-like receptor 9 stimulation). In this case, the cell surface le (30) is CD40 and the first reagent (6) can be any CD40 binding molecule that provides the desired tion signal, for example, the monoclonal antibody CP-870,893 or an antibody g fragment thereof such an a monovalent Fab fragment. The g partner C1 of the first agent (6) may, for example, be any affinity peptide that is fiased or conjugated to, for example, the C-terminus of one the two polypeptide chains (heavy or light chain) of the dy molecule. The binding partner C1 (6a) may, for example, be a streptavidin-binding peptide such as the peptide Trp-Ser-His-Pro-Gln—Phe-Glu-Lys (SEQ ID NO: 01), also known as the -tag®") that is described in US patent 5,506,121, for example, or streptavidin binding peptides having a sequential arrangement of two or more individual binding modules as described in International Patent Publication WO 02/077018 or US patent 7,981,632. When using a streptavidin binding peptide as binding r C1, the multimerization reagent (4) be any streptavidin mutein to which the streptavidin peptide (= first binding partner C1 (6a)) reversibly binds via its (biotin) binding sites Z1 (42) schematically shown in Fig. 1. Such a multimerization reagent may be a streptavidin mutein (analog) that comprises the amino acid sequence Va144*Thr45-A1a46-Arg47 (SEQ ID NO: 02) at sequence positions 44 to 47 of wild type streptavidin or a streptavidin mutein (analog) that comprises the amino acid sequence Gly45—Ala46—Arg47 (SEQ ID NO: 03) at sequence positions 44 to 47 of wild type streptavidin, both of which are described in US patent 6,103,493, for example, and are commercially available under the trademark Strep-Tactin®. In the Example of Fig. 1, the multimerization reagent (4) might r include multimeric calmodulin or glutathione-S- transferase, both of which form reversible bonds with calmodulin binding peptides or glutathione. Thus, the g site Z2 (44) can be formed by calmodulin or glutathione—S- transferase. Such a protein conjugate of for example, calmodulin with a streptavidin mutein can be made by standard protein chemistry, for example, by using bifunctional linkers.

As shown in Fig. lb, after contacting the cell population (2) with the multimerisation reagent (4) and usually incubating the cell population with the erization reagent (4), the population of cells (2) forms complexes/is bound to the erization agent via the first agent (6). The first agent binds specifically to the cell surface receptor molecule such as CD40 in this Example and provides the activation signal for cell expansion, of for example B cells. The other cell populations (22) contained in the initial sample that lack the specific cell surface molecule (30) do not bind to the multimerization reagent. In this respect, it is noted that the cell population (2) usually has multiple copies of the cell surface molecule (30) on its surface and binding of these multiple copies is typically needed for tion.

Thus, the multimerization agent (4) provide typically more than one binding site Z1 so that multiple first agents (6) can be reversibly bound to achieve merization" of the first agent, meaning to present the first agent in a sufficient density to the population of cells (2) (not shown in the scheme of Fig. 1). In this respect, it is noted that a erization agent as used herein can as such have multiple binding sites Z1, for example, a streptavidin mutein (being a etramer) in its native state has four such binding sites Z1. It is however also possible that the multimerization reagent is based on a compound that has as such only one g site Z1 for the reversible binding of a binding partner C1. Such an example is multimeric ulin. Calmodulin as such has only one g site for calmodulin binding peptides. However, calmodulin can be biotinylated and then d with streptavidin- oligomers (see also below), thereby providing a multimerization reagent in which multiple calmodulin les are presented in high density on a "scaffold", thereby providing multimeric calmodulin.

As shown in Fig.1c, after incubation (which is usually carried out over a period of time suitable to achieve expansion of the desired cell population) the binding between the binding partner Cl (6a) of the first agent (6) and the binding site 21 of the multimerization reagent (4) is disrupted by disrupting the respective ible bond. The tion may be ed by adding a competitor to the incubation/reaction e ning the population of cells (2) being bound to the multimerization reagent. For competitive disruption (which can be understood as being a competitive elution) of the reversible bond between the binding partner Cl (6a) of the first agent and the binding site Z1 (22) of the erization reagent, the incubation mixture/population of cells can be contacted with a free first binding partner Cl (20) or an analog of said first binding partner C that is e of disrupting the bond between the first binding partner Cl (6a) and the binding site Z1 (22). In the example of the binding partner Cl being a streptavidin binding peptide that binds to biotin g site of streptavidin, the first free partner Cl (20) may be the ponding free streptavidin binding peptide or an analogue that binds competitively. Such an analogue can, for example, be biotin or a biotin derivate such as obiotin.

As shown in Fig. 1d, addition of the first free partner (20) or the analogue thereof results in displacement of the binding r Cl (6a) from the multimerization reagent (4) and thus, since the binding partner Cl is sed in the first agent (6), displacement of the first agent (6) from the multimerization reagent (4). This displacement of the first agent (6) in turn results in a dissociation of the first agent (6) from the cell surface receptor (30), in particular if the binding affinity of the bond n the first agent and the cell surface receptor (30) has a dissociation constant (Kd) in the range of 10’2 M to 10'13 M and is thus also reversible. Due to this dissociation, the stimulation of the cell population (2) is also terminated. Thus, the present invention provides the advantage that the time period of the stimulation or expansion of the cell population can be exactly controlled and thus also the functional status of the cell population can be closely controlled. In this context, it is noted that the binding affinity of antibody molecules towards their antigen, including for example, a cell surface receptor molecule such as CD40 in this Example, is usually in the affinity range of the Kd of 10'7 M to ']3 M. Thus, conventional onal antibodies can be used as first agent (and also of course second agent as explained below) in the present invention. In order to avoid any unwanted y effects that lead to a stronger binding, monoclonal antibodies can also be used in form of their monovalent antibody fragments such as Fab-fragments or single chain Fv fragments.

In addition, due to the dissociation of the first agent from the cell e le (30), the present invention has the added advantage that the stimulated cell population is free of stimulating agents at the end of the stimulation period and that all other reagents used in the method, namely the first agent (6) as well as the fiee first partner (20) of the binding partner C1 or the analogue thereof can be easily removed from the ated cell tion (2) via a "removal cartridge" described in International patent application WC 2013/124474 while the multimerization reagent (4) being immobilized on a solid support such as a bioreactor e or a magnetic bead is being held back. Thus, reverting to the removal of the free agent (6) and the free first r (20), in accordance with the description of the "removal cartridge" in W0 24474 (see with reference to Fig. 4 thereof, for example), the elution sample obtained in Fig. 1d here can be loaded onto the second chromatography column ofWC 2013/124474. This tography column has a suitable stationary phase that is both an affinity chromatography matrix and, at the same time, can act as gel permeation matrix. This affinity chromatography matrix has an affinity reagent immobilized n. The affinity reagent may, in the case of the t Example, for instance, be streptavidin, a streptavidin mutein, avidin, an avidin mutein or a mixture thereof. The first agent (6), the free first partner (20) of the binding partner C1 (which is also called "competition reagent" herein) bind to the affinity reagent, thereby being immobilized on the chromatography . As a result the elution sample containing the isolated and expanded cell population (2) is being depleted of the first agent (6) and the competition reagent (20). The expanded cell population (2), being freed of any reactants, is now in a condition for further use, for example, for diagnostic applications (for example, further FACSTM sorting) or for any cell based therapeutic application.

Fig.2 shows a further embodiment of an expansion method of the invention. As shown in Fig. 23 a sample comprises a population of cells (2) that carry two specific cell surface molecules (30) and (32). The cell surface molecule (30) is involved in a primary activation signal to the cell population, while the cell surface molecule (32) is an ory molecule on the cell surface that is ed in ing a stimulus to the cells. The population of cells may, for example, be a T cell population in which the cell surface molecule (30) is a TClUCD3 complex and the cell surface molecule (32) is the accessory molecule CD28. Binding of both the TCR/CD3 x as the primary activation signal and CD28 as co-stimulant are necessary for expansion/proliferation ofT cells. The population of T cells (2) is in mixture with other cell populations (22) that lack the surface receptor les (30) and (32). Also in this embodiment, the cell population (2) is contacted with a multimerization reagent (4). The multimerization reagent (4) has ibly immobilized thereon (bound thereto) a first agent (6) that provides a primary activation signal to the cells. In addition, the erization agent has reversibly immobilized thereon (bound thereto) a second agent (8) that stimulates CD28 as accessory molecule on the surface of the cells.

The multimerization reagent (4) comprises at least one binding site Z1 (42) for the ible binding of the first agent (6) and the first agent (6) comprises at least one binding partner Cl (6a), wherein the binding partner Cl (6a) is able of reversibly binding to the binding site Z] (44) of the multimerization reagent. Thus, for immobilization, the first agent (6) is bound to the multimerization t (4) via the reversible bond formed between the binding partner Cl (6a) and the binding site 21 (42). In addition, in the Example illustrated in Fig. 2, the second agent (8) comprises a binding partner C2 (8a), wherein the binding r C2 is able of being reversibly bound to a binding site Z2 (44) of the multimerization reagent (4) The second agent (8) is bound to the multimerization reagent (4) via the reversible bond formed between the binding partner C2 (8a) and the binding site Z2 (44). In this Example, the first agent (6) might be a monoclonal anti-CD3-antibody or an antigen binding fragment thereof such as a Fab fragment. The second agent (8) might be a monoclonal anti- CD28 dy or an antigen binding fragment thereof such as Fab nt. The first binding partner (6a) might be a streptavidin binding peptide (6a) that is fused or conjugated to the anti- CD3 antibody or the anti-CD3 antibody fragment. The second binding partner (8a) might be calmodulin binding peptide that is also ated or fiised to the CD28 antibody or the CD28 binding dy fragment. In this context, it is noted that monoclonal antibodies against, for example, CD3 or CD28 are well-known (see, for example, US Patent 6,352,694 B or European Patent EP 0 700 430 B1 discussed above) and are commercially available from numerous suppliers such as Santa Cruz Biotechnology (Santa Cruz, CA, USA), Life Technologies, (Carlsbad, CA, USA), BD Biosciences (San Jose, CA, USA), Biolegend (San Diego, CA, USA) or Miltenyi Biotec (Bergisch Gladbach, Germany) to name only a few. Accordingly, such monoclonal antibodies can be used as first and second agent and can, for example, be chemically d (conjugated) with a binding partner C1 or C2. atively, it is also le to either clone the genes of the variable domains from the hydridoma cell line or use an antibody of which the amino acid sequence is known and produce a tive antibody fragment such as a Fab fragment or a FV recombinantly. When using such an approach as described herein in the Example section for both the hybridoma cell line OKT3 (ATCC® CRL- 8001TM, described in US Patent 4,361,549) that es a onal anti-CD3 antibody) and the anti-CD28 antibody 28.3 described by Vanhove et al, BLOOD, 15 July 2003, Vol. 102, No. 2, pages 564-570 and GenBank accession number AF451974.1, the binding partners C1 and C2 are conveniently provided by the respective expression vector used for the recombinant tion so that the antibody fragment s the binding partner C1 or C2 as a fusion peptide as the C-terminus of either the light or the heavy chain (In this context, the amino acid sequence of the le domain of the heavy chain and of the variable domain of the light chain of the antibody OKT3 that are described in Arakawa et al J. Biochem. 120, 657-662 (1996) are shown for ration purposes as SEQ ID NOS l7 and 18 and in the accompanying Sequence Listings, while the amino acid sequence of the variable domain of the anti-CD28 antibody 28.3 described by Vanhove et a1, supra, is shown as SEQ ID NOS 19 (VH) and 20 (VL) in the accompanying ce Listings). Also this methodology of cloning the variable domains of an antibody molecule and recombinantly producing a respective antibody fragment is well known to the person skilled in the art, see for example, , A. (1994) A general vector, pASK84, for cloning, bacterial production, and single-step purification of antibody Fab fragments. Gene 141, 79-84, or Skerra, A. (1993) Bacterial expression of immunoglobulin fragments. Curr Opin Immunol. 5, 256-562). Finally, it is also possible to generate dy molecules of artificial binding molecules with antibody like properties against a given target such as CD3 or CD28 as in the Example of Fig. 2 by nown evolutive methods such as phage display (reviewed, e.g., in Kay, B.K. et al. (1996) Phage Display of Peptides and Proteins — A Laboratory Manual, 1St Ed., Academic Press, New York NY; Lowman, H3. (1997) Annu. Rev. Biophys. Biomol. Stract. 26, 401—424, or Rodi, D.J., and Makowski, L. (1999) Curr. Opin. hnol. 10, 87—93), ribosome display (reviewed in Amstutz, P. et al. (2001) Curr. Opin. Biotechnol. 12, 5) or mRNA display as reported in Wilson, D.S. et a1. (2001) Proc. Natl. Acad. Sci. USA 98, 3750-3755.

In the case of the Example shown in Fig. 2, the multimerization reagent (4) has two different binding sites Z1 (42) and Z2 (44). With the g partner Cl (6a) being a streptavidin binding peptide, the g site Z1 (42) of the multimerization reagent (4) is provided by a suitable streptavidin mutein to which the streptavidin peptide (6a) reversibly binds. Since the binding C2 is a calmodulin binding e, the binding site Z2 (44) of the multimerization reagent (4) is provided by multimeric calmodulin. The multimerization reagent (4) can be a single le, for example a conjugate of multimeric calmodulin with streptavidin (this alternative would be usually used in case of a e multimerization) or can also consist of two ndent molecules. The latter option is preferred when the multimerization t (44) is immobilized on a solid support as shown in Fig.2 In this case, a mixture of a streptavidin mutein and ulin can be coated (immobilized) on the solid support, for example, in a 1:1 molar ratio with respect to the binding sites Z1 and Z2. In this context, it is noted that, due to the immobilisation of calmodulin on the surface of the solid support, there is no need to prepare multimeric calmodulin as explained above but immobilization of the calmodulin on the surface is sufficient to present calmodulin (that, as mentioned above, has only a single binding site for calmodulin binding peptides, in a sufficiently high density to ensure binding of the cell population (2). For example, in this case, a bivalent antibody fragment that has two binding sites against CD28 or an intact antibody that has per se two identical binding sites could be used as second reagent (8). id="p-27" id="p-27" id="p-27" id="p-27" id="p-27"

[0027] As shown in Fig. 2b, after contacting the T cell population (2) with the multimerisation reagent (4) and usually incubating the cell population with the erization reagent (4), the population of T cells (2) forms complexes/is bound to the erization agent Via the first agent (6) and the second agent (8). The first agent (6) and the second agent (8) bind specifically to the TClVCDS complex and the accessory le CD28, thereby inducing the T cells to proliferate/expand.

As shown in Fig. 2c, after incubation (which is usually carried out over a period of time suitable to achieve expansion of the desired cell population) the binding n the binding partner Cl (6a) of the first agent (6) and the binding site Z] of the multimerization reagent (4) is disrupted by disrupting the respective ible bond. Likewise, the binding between the binding partner C2 (8a) of the second agent (8) and the g site Z2 of the multimerization reagent (4) is disrupted by disrupting the respective reversible bond. The ible bond between the binding partner Cl (6a) of the first agent (6) and the binding site Zl can be disrupted by biotin (which acts as an analogue (20) of the free first partner) while the reversible bond between the g partner C2 (8a) of the first agent (8) and the binding site Z2 can be disrupted by the addition of a metal chelator um chelator) such as EDTA or EGTA (that acts an analogue (20) of the free second partner) since the binding of calmodulin to calmodulin binding peptides is m ion (Ca2+) dependent). This of course means that the contacting of the cell population (2) is carried out in a Call containing buffer.

As shown in Fig. 2d, addition of the analogue (20) of the first free partner and the second free partner, respectively results in displacement of the binding rs Cl (6a) and C2 (8a) from the multimerization reagent (4) and thus in cement of the first agent (6) and the second agent (8) from the multimerization reagent (4). This cement of the first agent (6) and second agent (8) in turn results in a dissociation of the first agent (6) and the second agent (8) from the TCIVCD3 complex and the accessory molecule CD28, thereby terminating the stimulation/expansion of the cell population (2). Thus, as said above, the present invention provides the advantage that the time period of the stimulation or expansion of a T cell population can be exactly controlled and therefore also the functional status of the tion of T cells can be closely controlled. After the elution of the cells as illustrated in Fig. 1d, the first agent (6), the second reagent (8) as well as the analogue (20) of free first r of the binding partner Cl and the second free partner of the binding r C2 can be easily removed from the stimulated cell tion (2) Via a "removal cartridge" described in International patent application WO 2013/ 124474. In addition, and importantly, in case the initial sample was a population of lymphocytes, for example, in form of PMBCs obtained from a Ficoll gradient, the T cell population (2) is now available for serial expansion as defined here. Since the expanded cell population (e. g. by an initial stimulation Via 28) can be transfected during expansion e.g. with a T cell receptor (TCR) or a chimeric antigen receptor (CAR, also known as artificial T cell receptor), the genetically modified cells can then be liberated from the initial stimulus and subsequently be ated with a second type of stimulus e.g. Via the de novo uced receptor. These second stimuli may comprise an antigenic stimulus in form of a peptide/MHC molecule, the cognate (cross-linking) ligand of the genetically introduced or (e.g. l ligand of a CAR) or any ligand (such as an antibody) that directly binds within the framework of the new receptor (e.g. by recognizing constant regions within the receptor). Thus, the T cell population ed from this serial expansion can be used for adoptive cell transfer.

Fig. 3 shows a further embodiment of an expansion method of the invention. Also the sample used in this Example comprises a population of T cells (2) that carry two specific cell surface molecules (30) and (32), with the cell surface molecule (30) being a TCIVCD3 complex and the cell surface molecule (32) being the accessory molecule CD28. In Fig. 3a the population of T cells (2) is shown alter being contacted with a multimerization reagent (4).

Also in this Example, the multimerization reagent (4) has reversibly immobilized thereon (bound thereto) as first agent (6) an D3 antibody or an antigen binding fragment f that provides a primary activation signal to the T cells and as second agent (8) an anti-CD28 antibody or an antigen binding fragment f that stimulates CD28 as accessory molecule.

The multimerization reagent (4) shown in the Example of Fig. 3 comprises only one type binding site Z1 (42) for the ible binding of both the first agent (6) and the second agent (8). Both the first agent (6) and the second agent (8) comprise at least one binding partner C1 (6a, 8a), wherein both the binding partner C1 (6a) and the g partner (8a) are able of reversibly binding to the binding site 21 (44) of the multimerization reagent.

Thus, for immobilization, the first agent (6) and the second agent (8), respectively are bound to the multimerization reagent (4) via the reversible bond formed between the g partner Cl (6a) and the binding partner C2 and the binding site Z1 (42). The binding partners C1 and C2 can either be different or identical. For example, the binding partner Cl can be a streptavidin binding peptide of the sequences Trp-Ser-His-Pro-Gln-Phe-Glu-Lys ((SEQ ID NO: 01), the "Strep-tag®") while the binding partner C2 can be the streptavidin binding peptide of the sequence Trp-Ser-His-Pro-Gln—Phe—Glu—Lys-(GlyGlyGlySer)3-Trp-Ser-His—Pro—Gln—Phe-Glu- Lys ((SEQ ID NO: 04), also known as "di—tag3")) or of the sequence Trp—Ser—His—Pro—Gln— Phe-Glu-Lys-(GlyGlyGlySer)2-Trp-Ser—His-Pro-Gln-Phe—Glu-Lys ((SEQ ID NO: 05), also known as "the di-tag2"), described by Junttila et al., Proteomics 5 (2005), 1199—1203 or US Patent 7,981,632). All these streptavidin binding peptides bind to the same binding site, namely the biotin binding site of streptavidin. If one or more of such streptavidin binding peptides is used as binding partners C1 and C2, the multimerization reagent (4) is a avidin mutein. As shown in Fig. 3, a soluble multimerization reagent (4) is used. In the case of a streptavidin mutein, this soluble multimerization reagent may, for example, be an oligomer or a r of streptavidin or avidin or of any mutein (analog) of streptavidin or avidin. The er may comprise three or more monomers of avidin, avidin or a mutein therof. The oligomer or polymer may be crosslinked by a polysaccharide. Such oligomers or rs of streptavidin or of avidin or of muteins of streptavidin or of avidin can in a first step be prepared by the introduction of carboxyl residues into a polysaccharide, e. g. dextran, essentially as described in "Noguchi, A., shi, T., Yamaguchi, T., Kitamura, K., Takakura, Y., a, M. & Sezaki, H. (1992). ation and properties of the immunoconjugate composed of anti-human colon cancer monoclonal dy and mitomycin C dextran conjugate. Bioconjugate Chemistry 3,132-137". In a second step, streptavidin or avidin or muteins thereof are coupled Via primary amino groups of internal lysine residue and/or the free N—terminus to the carboxyl groups in the dextran backbone using conventional carbodiimide chemistry. Alternatively, linked oligomers or rs of streptavidin or avidin or of any muten of streptavidin or avidin may also be obtained by crosslinking via bifunctional linkers such as glutardialdehyde or by other methods described in the literature.

Using as binding partners Cl and C2, moieties that bind to the same binding site (42) of the erization agent has the advantage that, as shown in Fig. 3b, the same free partner (of the first binding partner Cl and also of the second g partner C2) or analogue thereof can be used to terminate the expansion of the population of T cells (2) and to release this population of T cells (2) from the multimerization agent. In the Example of Fig. 3, an analogue of the first and second partner Cl and C2 such as biotin or a biotin derivate (iminobiotin or desthiobiotin) can be conveniently used for the termination of the expansion and the elution of the population of T cells (2). id="p-33" id="p-33" id="p-33" id="p-33" id="p-33"

[0033] As shown in Fig. 30, after the elution of the cells as illustrated in Fig. 1d, the first agent (6), the second reagent (8) as well as biotin as the analogue (20) of free first r of the binding partner Cl and the second free partner of the binding partner C2 can be easily d from the stimulated cell population (2) via a "removal cartridge" bed in ational patent application WO 2013/ 124474. In on, the embodiment of using a soluble multimerization reagent (4) has the further advantage of being able to avoid any solid support such as magnetic beads. This means there is no risk of contamination of the activated T cells by such magnetic beads. This also means that a process that is compliant with GMP standards can be much easier established compared to the known method such as the use of Dynabeads® in which onal measures have to be taken to ensure that the final expanded T cell population is free of ic beads. Furthermore, the use of a soluble multimerisation agent makes it much easier to remove the same from the activated cell population (T cells, B cells or also natural killer cells) since the cells can be simple sedimented by centrifugation and the supernatant including the soluble multimerization agent can be discarded. Alternatively, the soluble multimerization agent can be removed from the expanded cell population in a gel permeations matrix of the l cartridge of International patent application WO 2013/124474. Since no solid phase (e.g. magnetic beads) are present, the present invention also provides for an automated closed system for expansion of the cells that can be integrated into known cell expansion systems such as the Xuri Cell Expansion System W25 and WAVE Bioreactor 2/10 System, ble from GE Healthcare (Little Chalfont, Buckinghamshire, United m) or the Quantum® Cell ion System, available from TerumoBCT Inc.

(Lakewood, CO, USA).

Fig. 4 shows the results of an experiment in which CD3+ T responder cells were proliferated after being stimulated in vitro with (1CD3 and (1CD28 Fab fragments that were reversibly immobilized on beads coated with the streptavidin mutein Strep-tactin®. Fig. 4A in a histogram showing size-distribution (forward scatter) of ated cells, Fig. 4B s histograms representing the degree of eration according to the number of cells per cell division that are indicated on top of Fig. 4B (0 represents undivided cells; 5 ents cells that have gone through at least 5 divisions), and Fig. 4C shows a picture of the culture dish after 4 days of stimulation.

Fig. 5 shows the results of the differential ellular calcium mobilization in Jurkat cells that are either labelled with the (1CD3 antibody OKT3 or with Fab fragments of OKT3 being multimerized with Strep-tactin® (also referred to as Fab multimers herein). Fig. 5A: Jurkat cells were loaded with the calcium-sensitive dye Indo-l-AM and calcium release was triggered by injection of either (1CD3 mAb (black squares) or uCD3 OKT3 Fab multimers (derived from the parental cell line OKT3) with or without prior D-biotin disruption (dark grey triangles and light grey circles respectively) compared to injection of PBS (inverted white triangles). Application of ionomycine served as ve control. Time-resolved changes in intracellular Ca2+ tration were monitored by flow—cytometry based on the change in FL6/FL7 ratio. Fig. 5B: Indo-l-AM-labeled Jurkat cells were activated by different (1CD3 stimuli as described in Fig 4a; OKT3: upper graph and uCD3 Fab-multimer: middle graph) followed by subsequent (t=140s) D-biotin mediated disruption of uCD3 Fab-multimer signaling. Injection of PBS (lower graph) and ionomycine served as negative or positive control. Data are representative of three different experiments.

Fig. 6 shows the result of the reversible staining of cells by anti CD3 OKT3 Fab- multimers. y isolated PBMCs were stained with either a monoclonal antibody (left dot plot, parental clone for the Fab—multimers) or cognate PE-labeled ltimers and analyzed either before (second lefi column) or afier treatment with D-biotin (middle column).

Remaining Fab monomers were then detected after subsequent washing steps using fresh PE— labeled Strep—Tactin® (second right ). Secondary Fab-multimer staining of reversibly stained cells served as control (right column). Only live (PInegative) cells are shown. s in dot plots indicate the percentage of cells within gates.

Fig. 7 shows the isolation of cells by reversible g of anti-CD28 Fab nts multimerized with Strep-Tactin® labeled with phycoerythrine as a fluorescent label.

CD28+ cells were selected/isolation by Fab-multimer magnetic cell selection from freshly isolated PMBCs as described in ational Patent Application WO2013/011011. Before selection cells were control stained with either the cognate fluorescent aCD28-multimers (left dot plot) or with an dy directed against the globulin kappa light chain (second left dot plot, d-Ig kappa mAb). After selection, cells were treated with D-biotin and uently washed to remove magnetic beads and Fab-monomers. Liberated CD28+ cells were subsequently (re-)stained either with CD28 Fab-multimers (second right dot plot) or with the (x-Ig kappa mAb (right dot plot) to detect potentially remaining Fab-monomers. Only live (Plnegafive) CD3+ cells are shown. Numbers in dot plots indicate the tage of cells within gates.

Fig. 8 shows the results of an experiment in which CD3+ T responder cells were proliferated after being stimulated in vitro with reversible dCD3/0tCD28 Fab fragments that were reversibly immobilized on soluble oligomeric tactin® acting a soluble multimerization t. For the experiments the results of which are shown in Fig. 8, 300.000 CD3+ responder T cells (Tresp) were labeled with ZuM Carboxyfluorescein succinimidyl ester (CFSE) and stimulated with varying amounts of a preparation of soluble Streptactin oligomers on which a combination of 0LCD3 Fab fragment and (1CD28 Fab both carrying a Strep-tag as streptavidin binding peptide at the heavy chain were immobilized. ("lx" corresponds to 3ug multimerized Strep—tactin functionalized with 0.5ug (xCD3- and 0.5ug (1CD28 Fab; numbers indicate fold amount of "1x"). Tresp cells either left unstimulated or were stimulated with blank Strep-tactin multimers (no Fab) served as negative l.

Tresp cells were seeded in duplicates in 48-well plates along with 300.000 CD3 negative autologous feeder cells (irradiated with 30Gy) in lml cell e medium supplemented with 20U/ml eukin 2 (IL-2). Cells were incubated at 37°C without media ge and proliferation was analyzed according to CFSE on after 5 days by FACS analysis (Fig.

SB). Fig. 8A shows size distribution of cells after 5 days in culture. Histograms show live CD3+ cells, while Fig. 8C shows cells after e that were liberated by stimulation reagents after treated with lmM D-biotin and washed. The dissociation and removal of monomeric Fab fragments was analyzed by restaining with Strep-Tactin® labeled with phycoerythrine (ST- PE) as a fluorescent label and a entative histogram is shown. Fig. 8D shows the absolute number of live (trypan blue negative) cells after 5 days was counted using a Neubauer counting chamber and plotted against the respective stimulation condition. Median cell numbers are shown in Fig. 8D; error bars indicate standard ion (SD). Fig. 8E shows a picture of the culture dish after 5 days of stimulation.

Fig. 9 depicts an illustration of the serial expansion method of the present invention (Fig. 921) while Fig. 9b briefly describes some features and advantages of the serial expansion.

Fig. 10 shows an arrangement of the invention that can be used together with the expansion methods of the invention. This ement (100) includes a bioreactor (50), a first "removal cartridge" (70) and a second "removal cartridge" (90). The bioreactor (50) is fluidly ted to the first removable cartridge (70), and the first removal cartridge is fluidly connected to the second removal cartridge (90). This arrangement (100) can be part of a device for automated cell expansion and purification as described here.

In the bioreactor (50) an expansion method as described herein is carried out, for example an expansion method illustrated in Fig. 3 that makes use of a soluble multimerization reagent. In this case, after termination of the activation/expansion ofthe cell population (2) by addition of a itor (20) (free partner of the binding partner Cl or an analogue thereof) the reaction es that is released from the bioreactor contains the expanded population of cells (2), the first agent (6), the second agent (8) as well as the e multimerization reagent (4). In this example, the first agent (6) is a CD3 binding antibody fragment that includes a streptavidin binding peptide as binding partner C1, the second agent (8) is a CD28 binding antibody fragment that includes a avidin binding peptide as binding partner Cl and the competitor (20) (free analogue of the g partner C1) is biotin. This reaction e is applied on the first removal cartridge (70). This first removal cartridge (70) is a removal cartridge as described in International patent application W0 2013/124474 that includes a chromatography column with a suitable stationary phase. The stationary phase can serve both an affinity chromatography matrix and, at the same time, can act as gel permeation matrix.

This affinity chromatography matrix has an affinity reagent immobilized n. The affinity reagent may, in the case of the current Example, for instance, be streptavidin, a streptavidin mutein, avidin, an avidin mutein or a mixture thereof. Thus, the first agent (6) and the second agent (8) bind to the affinity reagent via their streptavidin g peptide. Also biotin as the competitor (20) binds to the affinity reagent. Thus, these three reagents are all being immobilized on the chromatography matrix of the first removal dge while the expanded cell population (2) and the soluble multimerization reagent (4) pass through the stationary phase. This "flow through" is then applied onto the second removal cartridge (90). Also this second l cartridge (90) ses a stationary phase. This stationary phase ses a second affinity reagent thereon which is able to bind to the binding site 21 (42) of the erization reagent (4). This affinity reagent may for example be biotin that is covalently bound to the stationary phase. Such a stationary phase may, for example, be d-biotin SepharoseTM obtainable from Affiland S.A. (Ans—Liege, Belgium). Thus, the soluble erization reagent (4) will be bound (retained) on the stationary phase of the second removal cartridge (90) while the expanded population of cells (2) passes through the stationary phase and is being freed of any reactants. The population of cells (2) is now in a condition for any r use, for example, for diagnostic ations (for example, further FACSTM sorting) or for any cell based therapeutic application. It is noted here that it is of course also possible to change the order of the first "removal cartridge" (70) and the second "removal cartridge" (90) in an arrangement (100), such that bioreactor (50) is (directly) fluidly ted to the second removable cartridge (90), and the first removal cartridge (70) is ed after and fluidly connected to the second removal cartridge (90). In this arrangement the multimerization reagent (4) will first be removed from the population of cells (2) and subsequently the first agent (6), the second (8) and e. g. the competitor (20) are removed. Such an arrangement is also encompassed in the present invention and can also be part of a device for automated cell expansion and purification as described here. id="p-42" id="p-42" id="p-42" id="p-42" id="p-42"

[0042] Fig. 11 shows a further embodiment of an arrangement of the invention that can be used together with the expansion methods of the invention. This arrangement (110) includes a bioreactor (50), a first "removal cartridge" (70) and a second al cartridge" (90). The bioreactor (50) is fluidly connected to the first removable cartridge (70), and the first l cartridge is fluidly connected to the second removal cartridge (90). In addition, the second removal cartridge (110) is fluidly connected to the bioreactor (50). This arrangement (110) can also be part of a device for automated cell expansion and purification as described here. When used, for example, together with an expansion method that employs a soluble multimerization reagent (4), a purified expanded population of cells (2) is obtained as eluate of the second l cartridge (90). Since the removal cartridge (90) is fluidly connected to the bioreactor (50), the population of cells (2) can be transferred back into the bioreactor (50), for example, to serial clonal expansion as described here, by transfecting the population of cells, for example, with the gene of an T cell receptor and subsequent further (second) expansion using an ion method of the invention.

Fig. 12 shows a further embodiment of an arrangement of the invention that can be used er with the expansion methods of the invention. This arrangement (120) includes a ctor (50), a first "removal cartridge" (70) and a second "removal cartridge" (90). The ctor (50) is fluidly connected to the first removable cartridge (70), and the first removal cartridge is fluidly connected to the second removal dge (90). r to the embodiment shown in Fig. 11, the second removal cartridge (110) is fluidly connected to the bioreactor (50). However, a "selection cartridge" (92) as described in International patent application W0 2013/124474 is ed in between the second removal cartridge (90) and the bioreactor (50).

Thus, a subpopulation of cells (2a) that is sed in the population of cells (2) can be selected/enriched via this "selection cartridge" (92) as described in . This subpopulation of cells (2a) can either be transferred into the bioreactor (50), for example, to undergo serial expansion as described here. Alternatively (not shown), this subpopulation of cells (2a) can be used for cell based therapy. It is again noted here that the use of a soluble multimerization reagent as described here allows the design of automated cell purification and expansion devices which are functionally closed and thus not prone to contamination. In addition, since soluble multimerization reagent avoids the need for solid phase als such as magnetic beads, such cell purification devices can be designed as continuous flow devices.

Fig. 13 shows the expansion kinetics iferation of purified CD4+ and CD8+ T responder cells (Tresp) that were stimulated in vitro either with (1CD3/(xCD28 Fab fragments or with aCD3/(xCD28/0LCD8 that were reversibly immobilized on two kinds of a soluble eric Strep-tactin® mutein acting as soluble multimerization reagent. The first kind of oligomeric Strep-tactin® was the fraction of the oligomeric streptavidin mutein (n2 3) obtained in Example 5 (also referred herein as "conventional actin® backbone", illustrated by the triangle symbol with the tip down in Fig. 13), the second kind of this oligomeric streptavidin mutein used as soluble multimerization reagent was an oligomer that was obtained by reacting the soluble oligomeric avidin mutein with biotinylated human serum albumin (HSA) This HSA based soluble multimerization reagent is also referred herein as "large Streptactin® backbone). In the experiments of Fig. 13 the expansion was d out without medium exchange. The results for the CD4+ T responder cells are shown in Fig.13A, the results for the CD8+ T der cells are shown in Fig. 138. In this context, it is noted that the experimentally used soluble erization reagents that were functionalized by reversibly binding first agents, and optionally second and third agents are referred to in the Figures as "Streptamer® multimers" Fig. 14 shows the expansion cs of proliferation of purified CD4+ and CD8+ T responder cells (Tresp) that were stimulated in vitro with (xCD3/(xCD28 Fab fragments that were ibly immobilized nts that were reversibly immobilized with two kinds of soluble oligomeric Strep-tactin® acting as soluble multimerization reagent. The first kind of eric Strep-tactin® was the fraction of the oligomeric streptavidin mutein (n2 3) ed in Example 5 (also referred herein as "conventional Streptactin® backbone", illustrated by the triangle symbol with the tip on top in Fig. 14), the second kind of this oligomeric streptavidin mutein used as soluble multimerization reagent was the HSA based soluble multimerization agent, the mentioned "large Streptactin® backbone"). In the experiments of Fig. 14 the expansion was carried out with medium exchange. The results for the CD4+ T responder cells are shown in Fig.14, the results for the CD8+ T responder cells are shown in Fig. 14B.

Fig. 15 shows the combined data from the results obtained in Figs 13 and 14 for the expansion cs of proliferation of purified CD4+ and CD8+ T responder cells, with Fig. 15A depicting the s for CD4+ T cells and Fig. 15B depicting the results for the CD8+ T cells. Straight lines are used for the culturing with medium ge on day 3, while dashed lines depict the values obtained for the degree of expansion without media exchange on day 3. The data shown in Fig. 15 are normalized on the input cell number. Only data for the Tresp stimulated with the oligomeric streptavidin mutein (n2 3), the Tresp stimulated with the commercially available Dynabeads (positive control) and the unstimulated T cells (negative control) are shown but no data on the multimerization reagent with the "large Streptactin® backbone".

Fig. 16 shows early cluster formation ofT cells after activation of purified CD4+ and CD8+ T der cells stimulated in vitro with ocCD3/(xCD28 Fab nts that were ibly immobilized on the soluble oligomeric streptavidin mutein (n2 3) described in e 5. Fig. 16A depicts the results for CD4+ T cells and Fig. 163 depicts the results for the CD8+ T cells. Data for the Tresp stimulated with the soluble multimerization reagent (the oligomeric streptavidin mutein), the Tresp stimulated with the commercially available Dynabeads (positive control) and the unstimulated T cells (negative control) are shown. id="p-48" id="p-48" id="p-48" id="p-48" id="p-48"

[0048] Fig. 17 shows the expansion kinetics and phenotype of CD3+ central memory T cells (Tcm) (CD3+CD62L+CD45RA-Tcm) polyclonally stimulated in vitro with uCD3/(1CD28 Fab fragments that were reversibly immobilized on the soluble oligomeric streptavidin mutein (with n: 3) described in Example 5. The graphs shown in Fig. 17 ent the degree of proliferation according to the number of cells harvested per time point, with Fig. 17A showing the proliferation in only IL-2 supplemented media and in Fig. 17B showing the eration in IL-2 and IL-15 supplemented media. Fig. 17C shows a flow- cytometric is of CD62L and CD127 e expression after 14 days of culture in these variable cytokine milieus.

Fig. 18 shows the kinetics of selective antigen-specific (Ag-specific) expansion out of a bulk population of purified CD3+CD62L+CD45RA- Tcm responder cells that were ated in vitro with both a peptidezMHC molecule complex (that acts as first agent that provides a primary activation signal to the cells) and uCD28 Fab fragment (that acts as second agent that binds the accessory molecule on the surface of the cells) and unstimulated T cells (negative control) are shown. Both, the complex of antigen-specific peptide with the MHC le and the (1CD28 Fab fragment were reversibly immobilized on the same soluble oligomeric streptavidin mutein (with n2 3) described in Example 5. The peptide used for the antigen—specific expansion in Fig. 18A was the peptide CRVLCCYVL (SEQ ID NO: 06), amino acids 309—317 of the ate-early 1 protein restricted by the 02 MHC molecule (described in Ameres et al, PLOS Pathogens, May 2013, vol. 9, issue 5, e1003383) representing an HLA—C7/IE-1 epitope that is specific for cytomegalovirus (CMV). The MHC I molecule that presents the peptide s at its C-terminus of the heavy chain the streptavidin binding peptide PQFEK(GGGS)2GGSAWSHPQFEK (SEQ ID NO: 07), that is commercially available as "Twin-Strep-tag®" from IBA GmbH, Gottingen, Germany). Fig. 18A shows exemplary flow-cytometric analysis for the fraction of the Ag-specific cells that were proliferated using the peptidezMHC-I complex specific for this HLA-C7/IE-1 epitope as first agent that provides a primary activation signal to the cells reversibly immobilized on the soluble oligomeric streptavidin mutein. The graphs in Fig.18B to Fig.18E rates the expansion kinetics of further Ag—specificities according to the number of specific peptidezMHCI multimer-positive cells ted per time point in analogy to Fig. 18A using distinct complexes of an antigen-specific peptide with the MHC I molecule as first agent that provides a primary activation signal to the cells reversibly immobilized on the soluble oligomeric streptavidin mutein. In more detail, Fig. 18B shows the expansion of Ag-specific cells that were expanded using the peptide2MHC-I complex specific for the pp65 e of CMV (amino acids 0 (QYDPVAALF, (SEQ ID NO: 08)) restricted by HLA-A2402), Fig. 18C shows the expansion of Ag-specific cells that were expanded using r peptidezMHC-I complex specific for the pp65 epitope of CMV (amino acids 4 RPHERNGFTV, (SEQ ID NO: 09)) cted by HLA-B702), Fig. 18D shows the expansion of Ag-specific cells that were proliferated using the peptidezMHC—I complex specific for the hexon 5 epitope of adenovirus (amino acids 4 TAYNSL, (SEQ ID NO: 10)) restricted by HLA-B702), Fig. 18E shows the expansion of Ag-specific cells that were proliferated using the peptide:MHC—I complex specific for the HLA-B7/IE-1309_317 epitope of CMV (exemplary FACS data see above Fig. 18A). All peptidezMHC molecules bearing the Twin Strep®-Tag are commercially available from IbaGmbH. In this context, the amino acid sequences of the HLA-A*2402, HLA-B*0702 and HLA-C*0702 molecules that carry the "Twin-Strep-tag®" as their C-terminus are shown as SEQ ID NO: 21, 22 and 23 in the accompanying ce Listings, while the amino acid sequence of the [32 microglobulin (which forms together with the Qt chain, that means the HLA encoded molecules the respective MHC I molecule) is shown as SEQ ID NO: 24 in the accompanying Sequence Listing. In addition, Fig.18F show exemplary flow-cytometric analysis of CD62L and CD127 surface expression after 14 days of culture for HLA-B7/Hexon5114_124 stimulated/expanded cells from Fig. 18D. id="p-50" id="p-50" id="p-50" id="p-50" id="p-50"

[0050] Fig. 19 shows the kinetics of selective Ag-specific expansion out of purified CD3+CD62L+CD45RA-Tcm responder cells that were stimulated in vitro with a) antigen specific peptide MHC I complexes and b) (xCD28 Fab nts that were reversibly immobilized as first and second agent on e oligomeric avidin muteins. For this purpose 500.000 CD3+CD62L+CD45RA— responder Tcrn cells (Tresp) were stimulated Ag— specifically using 3 ul of a preparation of actin multimerization reagent fimctionalized with 0.5ug peptidezMHC class I complexes equipped with a streptavidin binding peptide (the c peptide represents amino acids 4 (CPYSGTAYNSL, SEQ ID NO: 10) of the Hexon 5 protein of the irus cted by HLA-B0702, see above) and 0.5ug (xCD28 Fab. As an alternative, 4.5 ul of a preparation of Streptactin multimerization reagent loaded with 0.5ug this peptidezMHC class I complex, 0.5ug (1CD8 Fab and 0.5ug dCD28 Fab. For comparison, polyclonal stimulation was performed, using 3 ul of a preparation of Streptactin multimerization reagent (lmg/ml) either loaded with a combination of 0.5ug (1CD3 Fab and 0.5ug 0iCD28 Fab. Again as the ative stimulation condition bed above, 4.5 ul of a preparation of Streptactin multimers loaded with 0.5 ug 0LCD3 Fab, 0.5ug (1CD8 Fab and 0.5 ug (xCD28 Fab was used. Untreated (unstimulated) Tresp cells served as ve control and Tresp cells stimulated polyclonal with Dynabeads as positive control. Tresp cells were seeded in 48-well plates in lml cell culture medium supplemented with 30U/ml IL—2 and 5ng/ml IL- . Cells were incubated at 37°C with media exchange every 3 days and cell count was analyzed after 7 and 14 days. The photographs shown in Fig. 19 represent the degree of cluster formation on day 5 for Ag-specific ation as exemplified for the HLA-B7/Hexon 5 epitope of adenovirus.

Fig. 20 shows the yield and phenotype of expansion of purified CD8+ T responder cells stimulated in vitro with uCD3/aCD28 Fab fragments that were reversibly immobilized on two kinds of soluble oligomeric Strep-tactin® acting a soluble erization reagent. The first kind of eric Strep-tactin® was the fraction of the eric streptavidin mutein (nmericobtained in Example 5 (conventional backbone), the second kind of this oligomeric streptavidin mutein used as soluble multimerization reagent was the soluble oligomer bed above and referred herein as "large" Streptactin® backbone. In these experiments, the fraction of the oligomeric conventional streptavidin mutein (n2 3) was also used as a multimerization reagent that were either onalized with single Fab nts (third bar in Fig. 20A and Fig. 20B) or with a combination of (1CD3 and uCD28 Fab- fragments. rmore to the ed stimulation with uCD3/0tCD28 Fab fragments, also an additional (1CD8 Fab fragment (commercially available from IBA GmbH, Gottingen, Germany) was immobilized in order to test whether it is possible to preferentially stimulate a c T cell subpopulation. Fig. 20A shows a graph of bars that represent the degree of proliferation according to the number of cells harvested at day 6 compared to the negative controls (unstimulated purified CD8+ T responder cells) and normalized to the ve control (purified CD8+ T responder stimulated with commercially available ads (beads on which 0tCD3 and 0tCD28 monoclonal antibodies are irreversible immobilized). Fig. 203 shows flow-cytometric analysis of the surface expression of CD8 and the T cell surface molecule CD45RO (that is indicative of T cell proliferation and activation) after cell culture. The various ating conditions were compared using one-way ANOVA and no significant difference (n.s.) was detected.

Fig. 21 shows the yield and phenotype for the expansion of purified CD8+ T responder cells stimulated in vitro with tCD28 Fab fragments that were reversibly immobilized on soluble oligomeric Strep-tactin® acting as a soluble multimerization reagent that were either functionalized with single Fab fragments or with a combination of Fab- fragments (as already described above). In these experiments, the CD8+ T responder cells were stimulated with the soluble multimerization reagent (the soluble oligomeric Strep-tactin® l) of Example 5) which was functionalized with varying amounts of uCD3 and (XCD28 Fab fragments, optionally together with the uCD8 Fab fragment described above. The term ,,lx" corresponds to 1.5ug multimerized Streptactin onalized with 0.5 ug (xCD3 Fab fragment alone and 1.5ug multimerized Streptactin functionalized with 0.5ug uCD28 Fab alone), or 3 ul of a preparation of oligomeric Streptactin loaded with 0.5ug aCD3 Fab fragment and 0.5ug aCD28 Fab, or 4.5 ul of a preparation of Streptactin multimers loaded with 0.5ug strep-tagged aCD3, 0.5ug strep-tagged aCD8 and 0.5ug strep-tagged aCD28 Fab.

Accordingly, the term ,,2x" corresponds to 3.0 ug multimerized Streptactin functionalized with lug (xCD3 Fab fragment alone and 3.0 ug multimerized Streptactin fimctionalized with lug (1CD28 Fab alone, meaning that twice the amount of immobilized (xCD3 Fab fragment was used. Untreated Tresp cells served as negative control and purified CD8+ T responder stimulated with commercially available Dynabeads (beads on which (1CD3 and (1CD28 monoclonal antibodies are irreversible immobilized) as positive control. Fig. 21A shows a graphs in which the bars ent the degree of proliferation ing to the number of cells harvested at day 5 compared to the negative controls and normalized to the positive control.

Fig. 21B shows FACS analysis of CD8 and CD45RO surface expression after cell culture.

Fig. 22 shows the activation of intracellular signaling es of transduced Jurkat cells that have been modified to express an uCD19 chimeric antigen receptor (CAR), and that were stimulated using the oligomeric Strep-tactin® of Example 5 as soluble multimerization reagent. The specificity of a CAR is lly derived from a scFv region led from the antigen-binding region of a onal antibody (mAb) that specifically binds a target/tumor associated antigen such as CD19 and links it to T cell specific signaling ibed in Hudecek et al, Clin Cancer Res. 2013 June 15; 19(12): 3153—3164. In the experiments the extracellular domain (ECD) of CD19, which contains the natural ligand of the OLCD19 CAR as well as the polyclonal (ngG F(ab)2 fragment that recognizes the IgG4 spacer (donkey-anti—human F(ab)2 is cially available from Jackson Immuno Research) within the uCDl9-CAR were also used in this experiment as first agent that provides a primary tion signal to the jurkat cells. The reversibly immobilization to the soluble oligomeric streptavidin mutein was provided by the streptavidin peptide SAWSHPQFEK(GGGS)2GGSAWSHPQFEK (SEQ ID NO: 07) that was fused to the C- terminus of the ECD of CD19 or by the biotinylated (Fab)2 fragment of the ngG (since the avidin mutein "m2" binds biotin with reduced affinity, this binding is reversible and can for example be displaced by addition of an excess of free biotin). In the control experiment of Fig.22A 300.000 CD3+ Jurkat responder cells (Jresp) were stimulated with varying amounts of a mixture of ations of oligomeric Streptactin (lmg/ml) that was onalized with the aCD3 Fab and the (1CD28 Fab (,,xl" corresponds to 3ug multimerized Streptactin fimctionalized with 0.5ug aCD3- and 0.5 ug aCD28 Fab — polyclonal Streptamer multimer). In the experiment of Fig. 22B 3ul of a ation of the oligomeric Streptactin was fimctionalized with 0.5ug (x1) or lug (x2) of the extracellular domain (ECD) of CD 19 or with 3 ul of a preparation of the oligomeric actin loaded with 0.5ug (x1) or lug (x2) aIgG that recognizes the IgG4 spacer (which are both CAR-specific Streptamer® multimers). Jresp stimulated with Dynabeads (beads on which (1CD3 and aCD28 monoclonal antibodies are irreversible immobilized) or PMA and cin served as positive controls. Jresp cells were seeded in 1.5ml Eppendorf tubes in 200ul cell culture medium supplemented with 30U/ml IL- 2. Cells were incubated at 37°C and put on ice and lysed after 0 min to 20min of stimulation.

Fig. 23 shows the expansion of purified CD3+ T responder cells stimulated in vitro with dCD3/(xCD28 Fab fragments that were reversibly immobilized on the soluble oligomeric Strep-tactin® of Example 5 that served a soluble multimerization reagent. In one experiment, in addition to dCD3/dCD28 Fab fragments, also an (1CD8 Fab fragment commercially available from IBA GmbH, Gottingen, Germany (catalogue number 6 203) was immobilized on the soluble oligomer of the streptavidin mutein in order to test whether it is le to preferentially stimulate in vitro the CD8+ T cell ulation within the bulk CD3+ culture with a multimerization reagent of the invention having reversibly immobilized thereon also an aCD8 Fab fragment. In more , 500.000 purified CD3+ responder T cells ) were stimulated with 3 ul of a preparation of oligomeric Streptavidin (lmg/ml) loaded with a combination of 0.5ug of the (xCD3 and 0.5 ug of the (xCD28 Fab. As an ative approach, 4.5 ul of the Streptactin er were loaded with 0.5ug uCD3, 0.5 ug (xCD8 Fab and 0.5ug 0LCD28 Fab described above. Unstimulated Tresp cells served as negative control and Tresp ated with Dynabeads (beads on which (1CD3 and aCD28 monoclonal antibodies are irreversible immobilized) served as positive control.

Fig. 24 depicts exemplary strategies for the generation of oligomeric streptavidin muteins that can be used as soluble multimerization reagent of the invention. Fig. 24A shows that in a first step, the streptavidin mutein "m2" (SAm2) that comprises the amino acid sequence lle44-Gly45-Ala46-Arg47 (SEQ ID NO: 03) at sequence positions 44 to 47 ofwild type streptavidin is used for generation of oligomeric streptavidin muteins having a ntional backbone". In a second step, oligomeric soluble streptavidin muteins having a "large backbone" can be generated by either by coupling of avidin mutein with ylated carrier protein such as human serum albumin (HSA) or by coupling the streptavidin muteins with synthetic carriers such as PEG. Fig. 243: Biotinylation of human serum albumin (HSA).

DETAILED DESCRIPTION OF THE INVENTION The present invention provides methods, kits and an apparatus for expanding a population of cells or for ng a population ofT cells to proliferate.

The term "population of cells" as used herein encompasses all cells which can be expanded by binding to a cell surface receptor a first agent that provides a primary activation signal to the cells. It is also possible that for expansion of the population of cells, g of second agent to a second cell surface receptor (accessory molecule) might be needed to produce a co-stimulatory signal required for expansion of the cells. In some embodiments the cell population may be a population of lymphocytes ing, but not limited a population of B cells, a population of T cells or a population of natural killer cells. Illustrative examples of cell populations are B cells carrying CD40 or CD137 (both cell population can be proliferated upon binding of only a first agent that provides an activation signal, for e 4-1BB ligand; or an 0tCD40 antibody molecule or an 0LCD137 antibody molecule (see for example Zhang et al., 2010, J Immunol, 184:787-795)). Other illustrative examples for agents (either first or second) that may be used for the expansion ofB cells are agents that bind to IgG, CD19, CD28 or CD14, for example , aIgG, (1CD28, or aCD14 antibody molecules. It is also envisioned that first or second agents for the expansion ofB cell may comprise ligands for toll like receptors or interleukins, such as IL-21 (see for e Dienz O, et al. 2009. J. Exp.

Med. ). It is noted that lipopolysaccharide dependent activation of B cells is also encompassed in the present ion, as a lysaccharide can also be used as first agent and can be equipped with a binding partner C1 as used herein. Other illustrative examples of suitable cell populations include T cell population that expand after being activated by binding of a first agent to TCR/CD3 and binding of a second agent to an accessory molecule on the T cell such as CD28. In this case, the first agent ates a TCIUCD3 complex-associated signal in the T cells and the second agent provides a secondary stimulus by binding CD28 as accessory molecule. Agents that can be used for the expansion of T cells may also include interleukins, such as IL-2, IL-7, IL—15, or IL—21 (see for example Cornish et al. 2006, Blood. 108(2):600-8, Bazdar and Sieg, 2007, Journal of Virology, 2007, 81(22):]2670—12674, ia et a1, 2013, Immunology, :109-120). Other illustrative examples for agents that may be used for the expansion of T cells are agents that bind to CD8, CD45 or CD90, such as (1CD8, (1CD45 or (xCD90 antibodies. Illustrative examples of T cell population including antigen- specific T cells, T helper cells, cytotoxic T cells, memory T cell (an rative example of memory T-cells are CD62L+CD8+ specific central memory T cells) or regulatory T cells (an illustrative example of Treg are CD4+CD25+CD45RA+ Treg cells). The term "T cell (population)" as used herein also includes T cells that se a chimeric antigen receptor (CAR) that is also known as artificial T cell receptors or chimeric T cell receptors. Thus, a T cell population that ses a chimeric antigen receptor can also be expanded using the methods, reagents and devices of the present invention. See in this respect also Example 15 in which Jurkat cells that express a chimeric CD19 specific antigen receptor (CAR) were stimulated using a soluble multimerization reagent of the present invention. Another illustrative example of a suitable cell population includes natural killer cells (NK cells), which may for example be expanded with agents that bind to CD16 or CD56, such as for example (1CD16 or (1CD56 antibodies. In illustrative example for such an dCD16 dy is the antibody 3G8 with a VH sequence set forth in SEQ ID NO: 25 and a VL sequence set forth in SEQ ID NO: 26 (see for example o et al, Blood. 1991 Dec 15;78(12):3232-40.).

Another agent that may be used for expansion of NK cells may be IL-15 (see for example Vitale et al. 2002. The Anatomical Record. -92). Yet another illustrative example of a suitable cell population includes tes, which may for instance be expanded using an agent that binds to CD14, such as an dCD14 antibody molecule. The cell population can be of any ian origin, including but not limited to human, rabbit, guinea pig, squirrel, r, cat, dog, lemur, goat, pig, horse, rhesus monkey, macaque, or a chimpanzee.

Thus, in line with the above, this invention pertains to methods for selectively inducing ex vivo expansion of a population of cells such as B cells, T cells or natural killer cells in the absence of exogenous growth factors, such as lymphokines, and accessory cells. In addition, the proliferation of these cells such as B cells or T cells can be induced without the need for n, thus providing an expanded cell tion such as a T cell population which is polyclonal with respect to antigen reactivity. The methods disclosed herein may provide for sustained proliferation of a selected population of T cells such as CD4+ or CD8+ T cells over an extended period of time to yield a fold increase in the number of these cells relative to the original T cell population. In general, in case of a (clonal) ion of a lymphocyte population as described herein, all progeny may share the same antigen specificity as the cell population that was ed for ion.

Also in line with the above, provided by this invention are methods for expanding a population of antigen specific T cells. To produce a population of antigen specific T cells, T cells are contacted with an antigen in a form suitable to trigger a primary activation signal in the T cell, i.e., the n is presented to the T cell such that a signal is triggered in the T cell h the TCR/CD3 complex. For example, the antigen can be presented to the T cell by an antigen presenting cell in conjunction with an MHC molecule. An antigen presenting cell, such as a B cell, macrophage, monocyte, dendritic cell, Langerhans cell, or other cell which can present antigen to a T cell, can be incubated with the T cell in the presence of the antigen (e. g., a soluble antigen) such that the antigen presenting cell presents the antigen to the T cell.

Alternatively, a cell expressing an antigen of interest can be incubated with the T cell. For e, a tumor cell expressing tumor-associated antigens can be incubated with a T cell er to induce a tumor-specific response. Similarly, a cell infected with a pathogen, e.g., a virus, which presents antigens of the pathogen can be incubated with a T cell. Following antigen specific activation of a population of T cells, the cells can be ed in accordance with the methods of the invention. For example, after antigen specificity has been ished, T cells can be expanded by culture with an anti-CD3 antibody (used as first agent) and an anti- CD28 antibody (used as second agent) according to the methods described herein. In r embodiment, the first agent can be an MHC I: peptide complex, which binds to an antigen specific T cell population. In such an embodiment, any antigen specific peptide that is known and that can be complexed with the respective MHC I le can be used. See in this respect Examples 11 and 12 in which selective Antigen—specific expansion ofTom responder cells out of bulk CD3+ central memory T cells was exemplied for four different antigen- specific cells. Alternatively, it is also le to use as first agent the l ligand of a receptor that triggers of cell expansion. See in this respect Example 15 in which the extracellular domain of CD19 caused the activation of intracellular signaling cascades of transduced Jurkat cells that were modified to express ic CD19 binding antigen receptor (CAR).

The sample of the cell population can be from any suitable source, typically all sample of a body tissue or a body fluid such as blood. In the latter case, the sample might for example, be a population of peripheral blood mononucleated cells (PBMC) that can be obtained by standard isolation methods such a ficoll gradient of blood cells. The cell population to be expanded can however also be in purified form and might have been isolated using an reversible cell staining/isolation technology as described patent in US patent 7,776,562, US patent 8,298,782, International Patent application WOO2/054065 or International Patent ation WO2013/01 1011. Alternatively, the population of cells can also be obtained by cell sorting via negative magnetic immunoadherence as bed in US Patent 6,352,694 B1 or European Patent EP 0 700 430 B1. If an isolation method described here is used in basic research, the sample might be cells of in vitro cell culture experiments.

The sample will typically have been prepared in form of a fluid, such as a solution or dispersion.

In line with the above, in one embodiment the ion provides an in vitro- method of expanding a tion of cells, comprising contacting a sample comprising a population of cells with a multimerization reagent. The erization reagent has reversibly immobilized thereon (bound o) a first agent that provides a primary activation signal to the cells, wherein the multimerisation reagent comprising at least one binding site Z1 for the reversible binding of the first agent. The first agent comprises at least one g partner C1, wherein the binding r C1 is able of reversibly g to the binding site 21 of the multimerization reagent, wherein the first agent is bound to the multimerization reagent via the reversible bond formed n the binding partner C1 and the binding site Z1. The first agent binds to a receptor molecule on the surface of the cells, thereby ing a primary activation signal to the cells and thereby activating the cells.

In another embodiment, the invention provides a method, wherein the multimerization agent has reversibly immobilized thereon (bound thereto) a second agent that stimulates an accessory molecule on the surface of the cells. The second agent comprises a binding partner C2, wherein the binding partner C2 is able of being reversibly bound to a binding site Z2 of the multimerization reagent, wherein the second agent is bound to the erization reagent via the reversible bond formed between the binding r C2 and the binding site Z2. The second agent binds to the accessory molecule on the surface on the surface of the cells, thereby stimulating the activated cells. In this embodiment the first agent may stimulate a TCIUCD3 complex-associated signal in the T cells and may be a binding agent that specifically binds CD3. In this embodiment the accessory molecule on the T cell may be CD28 and the second agent that binds the accessory molecule is a binding reagent that specifically binds CD28. In this case, the first agent that specifically binds CD3 may be selected from the group consisting of an anti-CD3-antibody, a divalent dy fragment of an D3 antibody, a monovalent antibody fragment of an anti-CD3-antibody, and a proteinaceous CD3 g molecule with dy-like binding properties. Also the second agent that specifically binds CD28 may be selected from the group ting of an anti-CD28- antibody, a divalent antibody fragment of an anti-CD28 antibody, a monovalent antibody fragment of an anti-CD28-antibody, and a proteinaceous CD28 binding le with antibody-like binding properties. The divalent dy fragment may be an (Fab)2’-fragment, or a divalent single-chain Fv fragment while the monovalent antibody fragment may be selected from the group consisting of a Fab fragment, a Fv fragment, and a single-chain Fv fragment (scFv). A proteinaceous CD3 or CD28 binding le with antibody-like binding properties may be an aptamer, a mutein based on a polypeptide of the lipocalin family, a glubody, a protein based on the ankyrin scaffold, a protein based on the crystalline scaffold, an adnectin, and an aVimer.

In general the first and the second agent that is used in the present invention may, for ce be, an antibody, a fragment thereof and a proteinaceous binding molecule with antibody-like fimctions. Examples of (recombinant) antibody fragments are Fab fragments, FV fragments, single-chain FV fragments (scFV), a divalent antibody fragment such as an (Fab)2'- fragment, diabodies, triabodies (Iliades, P., et al., FEBS Lett (1997) 409, 1), decabodies (Stone, E., et al., l of Immunological Methods (2007) 318, 88—94) and other domain antibodies (Holt, L.J., et al., Trends hnol. (2003), 21, 11, 484—490). In some embodiments one or more binding sites of the first or second agent may be a bivalent naceous artificial binding molecule such as a dimeric lipocalin mutein that is also known as "duocalin". In some embodiments the receptor binding reagent may have a single second binding site, i.e., it may be monovalent. Examples of monovalent first or second agents include, but are not limited to, a monovalent antibody fragment, a naceous binding molecule with antibody-like binding properties or an MHC molecule. Examples ofmonovalent antibody fragments include, but are not limited to a Fab fragment, a FV fragment, and a single- chain FV fragment (scFV), including a divalent single-chain FV fragment.

As mentioned above, an example of a naceous g molecule with antibody-like fiinctions is a mutein based on a polypeptide of the lipocalin family (see for example, W0 03/029462, Beste et al., Proc. Natl. Acad. Sci. USA. (1999) 96, 903).

Lipocalins, such as the bilin binding protein, the human neutrophil gelatinase-associated lipocalin, human Apolipoprotein D or human tear lipocalin possess natural ligand-binding sites that can be modified so that they bind a given target. Further examples of a proteinaceous binding molecule with antibody-like g properties that can be used as a receptor binding reagent that specifically binds to the receptor molecule include, but are not limited to, the so— called ies (see e.g. international patent application WO 96/23879), proteins based on the ankyrin ld (Mosavi, L.K., et al., Protein Science (2004) 13, 6, 1435-1448) or crystalline scaffold (e.g. international patent application WO 01/04144) the proteins described in Skerra, J. Mol. Recognit. (2000) 13, 7, AdNectins, tetranectins and aVimers. AVimers, including multivalent aVimer proteins evolved by exon shuffling of a family of human receptor s, contain so called A-domains that occur as strings of multiple domains in several cell surface receptors (Silverman, J., et al., Nature Biotechnology (2005) 23, 1556-1561). ins, derived from a domain of human fibronectin, contain three loops that can be engineered for immunoglobulin-like binding to targets (Gill, D.S. & Damle, N.K., t Opinion in Biotechnology (2006) 17, 653-658). Tetranectins, derived from the tive human imeric protein, likewise contain loop regions in a C-type lectin domain that can be ered for desired binding (ibid.). Peptoids, which can act as n ligands, are oligomalkyl ) es that differ from peptides in that the side chain is connected to the amide nitrogen rather than the or carbon atom. Peptoids are typically resistant to proteases and other modifying enzymes and can have a much higher cell permeability than peptides (see e.g.

Kwon, Y.-U., and Kodadek, T., J. Am. Chem. Soc. (2007) 129, 1508-1509). Yet further examples of suitable proteinaceous binding molecules are an EGF-like domain, a Kringle- domain, a fibronectin type I domain, a fibronectin type II domain, a fibronectin type III domain, a PAN , a Gla domain, a SRCR domain, a Kunitz/Bovine pancreatic trypsin Inhibitor domain, tendamistat, a Kazal—type serine protease inhibitor domain, a l (P-type) domain, a von Willebrand factor type C , an Anaphylatoxin—like domain, a CUB domain, a thyroglobulin type I repeat, LDL-receptor class A domain, a Sushi domain, a Link domain, a Thrombospondin type I , an immunoglobulin domain or a an immunoglobulin-like domain (for example, domain antibodies or camel heavy chain antibodies), a C-type lectin domain, a MAM domain, a von Willebrand factor type A domain, a Somatomedin B , a WAP-type four disulfide core domain, a F5/8 type C domain, a Hemopexin domain, an SH2 domain, an SH3 domain, a Laminin-type EGF-like , a C2 domain, "Kappabodies" (cf. Ill. et al., Protein Eng (1997) 10, 949-57, a so called ody" (Martin et al., EMBO J (1994) 13, 5303-5309), a y (cf. Holliger et al., PNAS USA (l993)90, 6444-6448), a so called "Janusis" (cf. Traunecker et al., EMBO J (1991) 10, 3655- 3659, or Traunecker et al., Int J Cancer (1992) Suppl 7, 51—52), a nanobody, a microbody, an affilin, an affibody, a knottin, ubiquitin, a zinc-finger protein, an autofluorescent protein or a leucine-rich repeat protein. An example of a nucleic acid molecule with antibody—like functions is an aptamer. An aptamer folds into a defined three-dimensional motif and shows high affinity for a given target structure. id="p-65" id="p-65" id="p-65" id="p-65" id="p-65"

[0065] Turning now the multimerization reagent, the binding sites Z1 and Z2 of the multimerization agent can be identical (see also the Example of Fig. 3). In this case, a single multimerization agent may be used.

In the embodiment that a reversibly bond first and, optionally second agent is used, the multimerization reagent may be immobilized on a solid surface. Any solid surface (support) can be used for the immobilization of the multimerization reagent. rative examples of solid surfaces on which the multimerization reagent can be immobilized include a ic bead, a polymeric bead, a cell culture plate, a microtiter plate, a membrane, or a hollow fiber. Hollow fibers are, for example, used as bioreactor in the Quantum® Cell Expansion System, available from TerumoBCT Inc. (Lakewood, CO, USA). The multimerization reagent is usually covalently attached to the solid support, r, non- nt interactions can also be used for immobilization, for example on plastic substrates, if wanted. As also explained in more detail below, the multimerization reagent can, for example, be a streptavidin or avidin mutein that reversibly binds a streptavidin binding peptide. Such streptavidin muteins can be ntly attached to any surface, for example, resin (beads) used for chromatography purification and are commercially available in such form fiom IBA GmbH, gen, for example, as Tactin® Sepharose, Strep-Tactin® Superflow®, Strep-Tactin® ow® high capacity or Strep-Tactin® MacroPrep®. Other illustrative examples multimerization reagents that are readily commercially available are immobilized metal affinity chromatography (IMAC) resins such as the TALON® resins (Westburg, Leusden, The Netherlands) that can be used for the reversible immobilization of oligo- histidine tagged (his-tagged) proteins in general, meaning here, for the reversible binding of a first or a second agent that carries as first binding r C1 or second g partner C2 an oligohistidine tag such as an penta— or hexa-histidine tag. Other examples of multimerzation reagents are calmodulin sepharose available from GE Life Sciences which can be used together with a first or second agent that comprises a calmodulin g peptide as binding partner C1 or C2 or sepharose, to which glutathion is coupled. In the case, the binding partner C1 or C2 is glutathion-S-transferase. id="p-67" id="p-67" id="p-67" id="p-67" id="p-67"

[0067] In other embodiments of the method of the invention the multimerization reagent can be in a soluble form. In principle, the same multimerization agents can be used as in the case of a multimerization reagent that is immobilized on a solid support. The multimerization reagent is soluble form, can for example, be a streptavidin mutein oligomer, a calmodulin oligomer, a compound (oligomer) that provides least two chelating groups K, wherein the at least two chelating groups are capable of binding to a transition metal ion, thereby rendering moiety A capable of binding to an oligohistidine affinity tag, multimeric glutathione-S- transferase, or a ylated r protein.

As explained above, the first and second agent has, in addition to the binding site that is able to bind the respective cell surface receptor molecule, a binding r C1 or C2 (which will be referred to as "binding partner C" in the ing for the ease of reference).

This binding r C is able to bind to a binding site Z of the multimerization reagent (Z means either binding site Z1 or binding site 22 of the multimerization reagent) C. The non- covalent bond that is formed between the binding partner C that is included in the first or second agent and the binding site(s) Z of the multimerization reagent may be of any d th and affinity, as long as it is disruptable or reversible under the conditions under which the method of the invention is performed. The dissociation constant (KD) of the binding n the binding partner C that is included in the receptor binding t and the binding site Z ofthe multimerization reagent may have a value in the range from about 10'2 M to about ']3 M. Thus, this reversible bond can, for example, have a KD from about 10'2 M to about 10' M, or from about 10'3 M to about 10']2 M or from about 10'4 M to about 10'11M, or from about 10‘5 M to about lO'lOM. The KD of this bond as well as the K1), koff and kon rate of the bond formed between the binding site B of the receptor binding reagent and the receptor molecule can be determined by any suitable means, for example, by fluorescence titration, equilibrium dialysis or e n resonance. The receptor molecule binding reagent may include at least one, including two, three or more, second binding partners C and the affinity t may include at least two, such as three, four, five, six, seven, eight or more binding sites for the binding partner that is included in the receptor molecule binding reagent. As described in US patent 7,776,562, US patent 8,298,782 or International Patent application WO 2002/054065 any combination of a binding partner C and an affinity agent with one or more corresponding binding sites Z can be chosen, as long as the binding partner C and the binding site Z of the affinity agent are able to reversibly bind or multimerize in a (multivalent) complex, which typically goes along with an avidity effect. id="p-69" id="p-69" id="p-69" id="p-69" id="p-69"

[0069] The binding partner included in the first or second agent may be an oligopeptide, a polypeptide, a protein, a nucleic acid, a lipid, a saccharide, an oligosaccharide, or a polysaccharide. Such a g partner has a higher y to the binding site of the multimerization reagent than to other matter. Examples of a respective binding r include, but are not limited to, an immunoglobulin molecule, a fragment thereof and a proteinaceous binding le with antibody-like fiinctions.

In some embodiments the binding partner C that is included in the first or second agent includes biotin and the affinity reagent es a streptavidin analogue or an avidin analogue that reversibly binds to biotin.

In some embodiments the binding partner C that is included in the first or second agent includes a biotin analogue that reversibly binds to streptavidin or avidin, and the affinity reagent includes streptavidin, , a streptavidin analogue or an avidin analogue that ibly binds to the respective biotin analogue.

In some r embodiments the g partner C that is ed in the first or second agent includes a streptavidin or avidin binding peptide and the affinity reagent includes streptavidin, avidin, a streptavidin analogue or an avidin analogue that reversibly binds to the respective streptavidin or avidin binding peptide.

In some ments the g partner that is included in the first or second agent may include a streptavidin-binding peptide r—His-Pro-Gln-Phe—Glu-Lys (SEQ ID NO: 01) and the affinity reagent may include a streptavidin mutein gue) that comprise the amino acid sequence Val44-Thr45-Ala46-Arg47 (SEQ ID NO: 02) at sequence ons 44 to 47 of wild type streptavidin or the streptavidin mutein (analogue) that comprises the amino acid sequence lle44-Gly45-Ala46-Arg47 (SEQ ID NO: 03) at sequence positons 44 to 47 of wild type streptavidin, both of which are described in US patent 6,103,493, for example, and are commercially available under the trademark Strep-Tactin®. The streptavidin binding peptides might, for example, be single es such as the "Strep-tag®" described in US patent ,506,121, for example, or streptavidin binding peptides having a sequential arrangement of two or more individual binding modules as described in International Patent Publication W0 02/077018 or US patent 7,981,632.

In some embodiment the binding partner C of the first or second agent includes a moiety known to the skilled n as an affinity tag. In such an embodiment the affinity reagent includes a corresponding binding partner, for e, an antibody or an dy fragment, known to bind to the y tag. As a few illustrative examples of known affinity tags, the g partner that is included in the first or second agent may include an oligohistidine, an immunoglobulin domain, maltose-binding protein, glutathione-S-transferase (GST), chitin binding protein (CBP) or thioredoxin, calmodulin binding peptide (CBP), FLAG-peptide, the HA-tag (sequence: Tyr-Pro-Tyr-Asp-Val-Pro-Asp-Tyr-Ala, (SEQ ID NO: 11)), the VSV-G-tag (sequence: Tyr-Thr-Asp-Ile-Glu-Met-Asn-Arg-Leu-Gly-Lys, (SEQ ID NO: 12)), the HSV-tag (sequence: Gln-Pro-Glu-Leu-Ala-Pro-Glu-Asp-Pro-Glu-Asp, (SEQ ID NO: 13)), the T7 epitope (Ala-Ser-Met—Thr-Gly-Gly-Gln-Gln-Met—Gly, (SEQ ID NO: 14)), maltose g protein (MBP), the HSV epitope of the sequence Gln-Pro-Glu-Leu-Ala-Pro— Glu-Asp-Pro-Glu-Asp (SEQ ID NO: 13) of herpes simplex Virus glycoprotein D, the "myc" epitope of the transcription factor c-myc of the sequence Glu—Gln—Lys—Leu—Ile—Ser—Glu—Glu— Asp-Leu (SEQ ID NO: 15), the V5-tag (sequence: Gly-Lys-Pro-I1e-Pro-Asn-Pro-Leu-Leu-Gly- Leu-Asp-Ser-Thr, SEQ ID NO: 16), or glutathione-S-transferase (GST). In such an embodiment the complex formed between the one or more binding sites of the multimerisation t, in this case an antibody or antibody fragment, and the antigen can be disrupted competitively by adding the free antigen, i.e. the free peptide (epitope tag) or the free protein (such as MBP or CBP). The affinity tag might also be an oligonucleotide tag. Such an ucleotide tag may, for instance, be used to hybridize to an oligonucleotide with a complementary ce, linked to or included in the affinity reagent.

In some embodiments the binding between the binding partner C that is included in the first or second agent and one or more binding sites of the multimerization reagent occurs in the presence of a divalent, a trivalent or a tetravalent cation. In this regard in some embodiments the multimerization t includes a divalent, a trivalent or a tetravalent cation, typically held, e.g. complexed, by means of a suitable chelator. The binding partner that is ed in the receptor binding reagent may in such an embodiment e a moiety that includes, e.g. complexes, a divalent, a trivalent or a tetravalent cation. Examples of a respective metal chelator, include, but are not limited to, ethylenediamine, ne- diaminetetraacetic acid (EDTA), ethylene glycol cetic acid (EGTA), diethylenetri— aminepentaacetic acid (DTPA), s(carboxymethyl)glycine (also called nitrilotriacetic acid, NTA), or l,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA). As an example, EDTA forms a complex with most monovalent, divalent, trivalent and tetravalent metal ions, such as e. g. calcium (Ca2+), ese (Mn2+), copper (Cu2+), iron (Fe2+), cobalt (Co3+) and zirconium (Zr4+), while BAPTA is specific for Ca2+. As an illustrative example, a standard method used in the art is the formation of a complex between an oligohistidine tag and copper (Cu2+), nickel , cobalt (C02+), or zinc (Zn2+) ions, which are presented by means of the chelator otriacetic acid (NTA), In some embodiments the binding partner C that is included in the first or second agent includes a calmodulin binding peptide and the affinity reagent es multimeric calmodulin as described in US Patent 5,985,658 or as described herein with reference to Figure 2, for example. In some embodiments the binding partner C that is included in the first or second agent includes a FLAG peptide and the affinity reagent includes an antibody that binds to the FLAG peptide, e.g. the FLAG peptide, which binds to the monoclonal antibody 4E1 l as described in US Patent 4,851,341. In one ment the binding partner C that is ed in the first or second agent includes an oligohistidine tag and the affinity reagent includes an antibody or a transition metal ion binding the oligohistidine tag. The disruption of all these binding complexes may be accomplished by metal ion ion, e.g. calcium chelation, for instance by adding EDTA or EGTA (supra). Calmodulin, antibodies such as 4Ell or chelated metal ions or free chelators may be erized by conventional methods, e.g. by ylation and complexation with streptavidin or avidin or multimers thereof or by the introduction of carboxyl residues into a polysaccharide, e.g. dextran, essentially as described in Noguchi, A, et a1. Bioconjugate Chemistry (1992) 3, 132-137 in a first step and linking calmodulin or antibodies or chelated metal ions or free chelators via primary amino groups to the carboxyl groups in the polysaccharide, e.g. dextran, backbone using conventional carbodiimide chemistry in a second step. In such embodiments the binding between the g partner C that is included in the first or second agent and the one or more g Sites Z of the multimerization reagent can be disrupted by metal ion chelation. The metal chelation may, for example, be accomplished by addition of EGTA or EDTA.

In some ments, in particular, if the multimerization reagent is in soluble form and is based on avidin or avidin, it is an oligomer or a polymer of streptavidin or avidin or of any mutein (analogue) of streptavidin or avidin. The binding site Z is the l biotin binding of avidin or streptavidin. The respective oligomer or polymer may be crosslinked by a polysaccharide. In one embodiment oligomers or polymers of avidin or of avidin or of s (analogs) of streptavidin or of avidin are prepared by the introduction of yl residues into a polysaccharide, e. g. n, essentially as described in Noguchi, A, et al., Bioconjugate Chemistry (1992) 3,132-137 in a first step. Then streptavidin or avidin or analogues thereof may be linked via primary amino groups of internal lysine e and/or the free N—terminus to the carboxyl groups in the dextran backbone using conventional carbodiimide chemistry in a second step. In addition, linked oligomers or polymers of streptavidin or avidin or of any mutein (analogue) of streptavidin or avidin may also be obtained by crosslinking individual streptavidin or avidin molecules (the tetrameric homodimer of streptavidin or avidin is referred herein as an "individual molecule" or smallest building block of a respective oligomer or polymer) via bifunctional molecules, serving as a linker, such as glutardialdehyde or by other s described in the art. It is, for example, le to generate oligomers of streptavidin muteins by introducing, in a first step, thiol groups into the streptavidin mutein (this can, for example, be done by reaction the streptavidin mutein 2-iminothiolan (Trauts reagent) and by activating, in a separate on amino groups available in the streptavidin mutein. This activation of amino groups can be achieved by reaction of the avidin mutein with a commercially available heterobifianctional crosslinkers such as sulfosuccinimidyl 4-(N-maleimidomethyl)cyclohexane-l-carboxylate (sulfo SMCC) or Succinimidyl[([3-maleimidopropionamido)hexanoate (SMPH). In a second step, the two reaction products so obtained are mixed together, leading to the reaction of the thiol groups contained in the one batch of modified streptavidin mutein with the activated (by id functions) amino acids of the other batch of modified streptavidin . By this reaction, multimers/oligomers of the streptavidin mutein are formed. These oligomers can have any suitable number of "individual molecule" or streptavidin building block" higher than 3 and the oligomerization degree can be varied according to the reaction condition (see Fig. 24). After reacting these two batches of the modified streptavidin mutein, the ric soluble erization reagent is typically isolated via size exclusion chromatography and any desired fraction can be used as multimerization reagent. Typically, the oligomers do not have (and do not need to have) a single molecular weight but they usually observe a statistical weight distribution such as Gaussian distribution. Any oligomer with more than three streptavidin homotetramers (building blocks; (11: 3)) can be used as soluble erization reagent. The oligomers might have, for example from 3 to 25 steptavidin mutein homotetramers. With a molecular weight of about 50 kDa for streptavidin muteins such as the mutein "ml" or "m2" described in more detail below, these soluble oligomers have a lar weight from about 150 kDa to about 1250 kDa. Since each streptavidin molecule/mutein has four biotin binding sites such a multimerization reagent provides 12 to 100 g sites Z1 (and Z2) as described herein.

In accordance with the above disclosure, in addition to such eric erization reagents that only contain cross-linked streptavidin homotetramers, it is le to react tetrameric streptavidin muteins to a carrier to obtain multimerization reagents that are used in the present invention. In addition to the above described reaction with a polysaccharide, it is also possible to use physiologically or pharmaceutically acceptable proteins such as serum albumin (for example human serum albumin (HSA) or bovine serum albumin (BSA) as carrier protein. In such a case, the streptavidin mutein (either as individual homo-tetramer or also in the form of oligomers with n2 3) can be coupled to the carrier protein via non-covalent interaction. For this purpose, biotinylated BSA (which is commercially available from various suppliers such as ThermoFisher Scientific, Sigma Aldrich or Vectorlabs, to name only a few) can be reacted with the streptavidin . When so doing, some of the streptavidin oligomers will non-covalently bind via one or more biotin g sites (Z1, Z2) to the biotinylated carrier protein, leaving the majority of the binding sites (Z1, Z2) of the er available for binding the agents such as the first agent and optionally the second agent and any further agent as described herein. Thus, by such an approach a soluble erization reagent with a multitude ofbinding sites Z1 can be conveniently ed (see Fig. 24). Alternatively, a streptavidin mutein r as individual homo-tetramer or also in the form of oligomers with n2 3) can be covalently coupled to a synthetic carrier such as a polyethylene glycol (PEG) molecule. Any suitable PEG le can be used for this purpose, as long as the PEG molecule and the respective multimerization reagent is soluble. Typically, PEG molecule up to a molecular weight of 1000 Da are all soluble in water or culture media that may be used in the present invention. Such PEG based multimerization reagent can be easily prepared using cially available activated PEG molecules (for example, PEG- NHS derivatives available from NOF North America Corporation, Irvine, California, USA, or ted PEG derivatives available from Creative PEGWorks, Chapel Hills, North Carolina, USA) with amino groups of the streptavidin mutein. id="p-79" id="p-79" id="p-79" id="p-79" id="p-79"

[0079] Under streptavidin or wild-type streptavidin (wt-streptavidin), the amino acid sequence disclosed by Argarana et a1., Nucleic Acids Res. 14 (1986) 1871-1882 is referred to.

Streptavidin muteins are polypeptides which are distinguished from the sequence of wild-type streptavidin by one or more amino acid substitutions, deletions or ons and which retain the binding properties of wt—streptavidin. Streptavidin-like polypeptides and streptavidin muteins are polypeptides which essentially are logically equivalent to ype streptavidin and are in particular capable of binding , biotin derivative or biotin analogues with the same or different affinity as wt—streptavidin. Streptavidin-like polypeptides or streptavidin muteins may contain amino acids which are not part of wild-type streptavidin or they may include only a part of wild-type streptavidin. Streptavidin-like polypeptides are also polypeptides which are not cal to wild-type streptavidin, since the host does not have the enzymes which are required in order to transform the host-produced ptide into the structure of wild-type streptavidin. The term "streptavidin" also includes streptavidin tetramers and streptavidin dimers, in particular streptavidin homotetramers, streptavidin homodimers, streptavidin heterotetramers and strepavidin heterodimers. Each subunit normally has a g site for biotin or biotin analogues or for streptavidin-binding peptides. Examples of avidins or streptavidin muteins are ned, for example, in WO 86/02077, DE 19641876 Al, US 6,022,951, WO 98/40396 or WO 96/24606.

In a preferred embodiment, streptavidin muteins that are used as multimerization reagent are those avidin muteins which are described in US Patent 6,103,493 and also in DE 196 41 8763. These avidin muteins have at least one on within the region of amino acid positions 44 to 53, based on the amino acid sequence of wild-type streptavidin.

Preference is given to muteins of a minimal streptavidin, which start N—terminally in the region of amino acids 10 to 16 of wild-type streptavidin and end C-terminally in the region of amino acids 133 to 142 of ype streptavidin. Examples of such preferred streptavidin muteins have a hydrophobic aliphatic amino acid instead of Glu at on 44, any amino acid at position 45, a hydrophobic aliphatic amino acid at position 46 or/and a basic amino acid instead of Val at position 47. The streptavidin mutein may be a mutein that comprises the amino acid sequence Va144-Thr45-Ala46-Arg47 (SEQ ID NO: 02) at sequence positions 44 to 47 or the streptavidin mutein (analog) that comprises the amino acid sequence lle44-Gly45-Ala46- Arg47 (SEQ ID NO: 03) at sequence positions 44 to 47 of wild type streptavidin, Such muteins are described in US patent 6,103,493, for example, and are commercially available from IBA GmbH in the form of mutein "m1" and mutein "m2" under the trademark Strep-Tactin®. id="p-81" id="p-81" id="p-81" id="p-81" id="p-81"

[0081] A method according to the present invention may in some embodiments be used to deplete a sample of reagents that have previously been used in cell ion. The first or second agent and the respective free partner (the competition agent) may, for instance, be present included in the eluate of an ion method as described above. Using a method according to the invention such reagents may be at least essentially, including entirely removed from a sample, e.g. from a cell population. As an illustrative example, a first or second agent as defined above may be depleted from a sample to levels that are below the detection limit of e.g. FACS or Western Blot. A competition reagent (free first or second binding partner or analogue thereof) may have been used in order to terminate and control the expansion and release the cell population form the multimerization agent. This competition reagent may have a binding site that is e of specifically binding to the binding site Z of the affinity t in a al cartridge" of WC 2013/ 124474. In such an embodiment the respective method of the invention may also serve in depleting the first and second agent and the competition reagent, including removing the same.

A method according to the t invention may be d out at any temperature at which the Viability of the cell population is at least essentially uncompromised.

When reference is made herein to conditions that are at least essentially not harmful, not detrimental or at least essentially not compromising ity, conditions are ed to, under which the percentage of the population of cells that are to be expanded with full viability, is at least 70 %, including at least 75 %, at least 80 %, at least 85 %, at least 90 %, at least 92 %, at least 95 %, at least 97 %, at least 98 %, at least 99 % or at least 99.5 %. In some embodiments a method according to the invention is carried out at a temperature of about 20 °C or higher. Depending on the cell tion to be expanded a le temperature range may for instance be from about 20 0C to about 45 °C, including from about 25 °C to about 40 °C, or from about 32 °C to 37 °C. In some ments a method according to the ion is carried out at a constant temperature value, or at a selected temperature value :: about 5 °C, i about 4 °C, :: about 3 CC, i about 2 °C, i about 1 °C or i about 0.5 0C. The person skilled in the art is able to empirically determine a suitable temperature, taking into account the nature of the cells and the expansion conditions. Typically human cells are expanded at a temperature such as 37 °C.

In a further embodiment, the invention provides an in vitro-method of expanding a population of cells, comprising contacting a sample sing a population of cells with a multimerization reagent, n the multimerization reagent is in a soluble form and has immobilized n (bound thereto) a first agent that es a primary tion signal to the cells. The multimerization reagent comprises at least one binding site Zl for the binding of the first agent, wherein the first agent comprises at least one binding partner Cl, wherein the binding partner Cl is able of g to the binding site Z] of the multimerization reagent. The first agent is bound to the multimerization reagent via the bond formed between the binding partner Cl and the binding site Z1, and the first agent binds to a receptor molecule on the surface of the cells, thereby providing a y activation signal to the cells and thereby activating the cells. It is expressly noted here that when a soluble multimerization agent is used, the bond between the binding part Cl and the binding site Zl does not need to be reversible. id="p-84" id="p-84" id="p-84" id="p-84" id="p-84"

[0084] In an embodiment of this second the multimerization agent has immobilized thereon (bound thereto) a second agent that ates an accessory molecule on the surface of the cells, wherein the second agent comprises a binding partner C2, wherein the binding partner C2 is able of being bound to a binding site Z2 of the multimerization reagent. The second agent is bound to the multimerization reagent via the bond formed between the binding partner C2 and the binding site Z2, wherein the second agent binds to the accessory molecule on the surface on the surface of the cells, thereby stimulating the activated cells.

In one embodiment of this second method, the bond formed between the binding partner Cl and the binding site 21 may be irreversible and/or also the bond formed between the binding partner C2 and the binding site Z2 may be irreversible. id="p-86" id="p-86" id="p-86" id="p-86" id="p-86"

[0086] In a different embodiment of this second , the bond formed between the binding partner Cl and the binding site Z1 may be reversible. Also the bond formed between the binding r C2 and the binding site Z2 may be reversible. In this case, the dissociation constant (Kd) for the reversible binding between said binding site Z1 and said g partner C1 and/or for the reversible binding between said binding site Z2 and said binding partner C2 may be in the range of 10'2 M to 10'13 M.

In this second method that is based on a soluble multimerization reagent, the first and second reagent as well as the multimerization reagent and all other reagents and cell populations can ise be used in the same manner as disclosed above for the method that makes use of reversible between the first or second agent and the multimerization reagent.

The invention further es a reagent kit for expanding a population of cells, the kit comprising (i) a erization reagent, wherein the multimerization reagent comprises at least one binding site Z for the reversible binding of a first agent, (ii) a first agent that binds to a receptor molecule on the e of the cells, thereby providing a primary activation signal to the cells and thereby activating the cells, wherein the first agent comprises at least one binding partner Cl, wherein the binding partner Cl is able of reversibly binding to a g site Zl of the multimerization reagent, wherein the first agent is bound to the multimerization reagent via the reversible bond formed between the binding partner C1 and the binding site Zl and (iii) a second agent that stimulates an accessory molecule on the surface of the cells, wherein the second agent comprises a binding partner C2, wherein the binding partner C2 is able of reversibly binding to a binding site Z2 of the multimerization reagent, wherein the second agent is bound to the multimerization reagent via the bond formed between the g partner C2 and the binding site Z2, wherein the second agent binds to the accessory molecule on the surface on the surface of the cells, y stimulating the activated cells.

The invention also provides a reagent kit for expanding a population of cells, the kit comprising (i) a multimerization reagent, wherein the multimerization t is in soluble form and comprises at least one binding site Z for the reversible binding of a first agent, (ii) a first agent that binds to a receptor molecule on the surface of the cells, thereby providing a y activation signal to the cells and thereby activating the cells, wherein the first agent ses at least one g r Cl, wherein the binding partner Cl is able of binding to a binding site Z] of the multimerization reagent, wherein the first agent is bound to the multimerization reagent via the reversible bond formed between the g partner Cl and the binding site Z1.

This second reagent kit may further comprises (iii) a second agent that stimulates an accessory molecule on the surface of the cells, wherein the second agent comprises a binding partner C2, wherein the binding partner C2 is able of binding to a binding site Z2 of the multimerization t, wherein the second agent is bound to the multimerization reagent via the bond formed between the binding partner C2 and the g site Z2.

A kit as disclosed herein is in particular used when the population of cells is a lymphocyte population.

In accordance with the disclosure above, the invention also provides novel multimerization reagents and novel composition comprising multimerization reagents that care e of ing a population of cells. Such a multimerization reagent that is capable of expanding a population of cells is a multimerisation reagent that is in soluble form and comprises at least one binding site Z1 for the reversible binding of a first agent that provides a primary activation signal to the cells, wherein the multimerization t has reversibly immobilized thereon (bound thereto) said first agent that provides a primary activation signal to the cells; wherein the first agent comprises at least one binding partner C1, n the binding r C1 is able of reversibly binding to the at least one binding site Z] of the multimerization reagent, wherein the first agent is bound to the multimerization t via the reversible bond formed between the binding partner C1 and the binding site Z1. It should be noted here that such a multimerization agent can have immobilized n any of the first agent that are described herein.

A multimerization reagent of the invention may further comprise at least one binding site Z2 for the reversible binding of a second agent that stimulates an accessory molecule on the surface of the cells, wherein the multimerization reagent has reversibly immobilized thereon (bound o) the second agent that stimulates an accessory molecule on the surface of the cells, wherein the second agent comprises a g partner C2, wherein the binding partner C2 is able of binding to the at least one g site ZZ of the multimerization reagent. In this embodiment the second agent is bound to the multimerization reagent via the bond formed between the binding partner C2 and the binding site Z2.

Also in line with the disclosure given above, such a multimerization reagent is capable of ing a cyte population or a subpopulation contained in the lympocyte population. The lymphocyte population to be expanded may any suitable population, for example, a B cell population, a T cell population, or a l killer cell population. The T-cell population may be an antigen-specific T cell tion, a T helper cell population, a cytotoxic T cell, a memory T cell, a regulatory T cell, or a l killer T cell population. Accordingly, in such embodiments of the multimerization reagent the first agent is able to stimulate a TCR/CD3 complex-associated signal in the T cells. The first agent present in the multimerization t may thus be binding reagent that specifically binds CD3, while the second agent that binds the accessory molecule may be a binding agent that specifically binds CD28 or CD137.

In embodiments of the multimerization reagent the first agent that specifically binds CD3 may be an anti-CD3-antibody, a divalent antibody fragment of an anti-CD3 antibody, a lent antibody fragment of an anti-CD3-antibody, and/or a proteinaceous CD3 g le with antibody-like binding properties. In these embodiments, the second agent that specifically binds CD28 or CD137 may be an anti-CD28-antibody, a divalent antibody fragment of an D28 antibody, a monovalent antibody fragment of an anti-CD28-antibody, a proteinaceous CD28 binding molecule with antibody—like binding properties, an anti-CD137-antibody, a divalent antibody fragment of an D137 antibody, a lent antibody fragment of an D137-antibody, a proteinaceous CD137 binding molecule with antibody-like binding properties, 4-1BB ligand, and any mixture thereof. Thus, a multimerization reagent of the invention can generally have immobilized thereon one kind of first agent and a mixture of second agents, for example, an anti-CD3 antibody as first agent and for example, an anti-CD28 antibody and 4-1BB ligand as (joint) second agents.

If the multimerization reagent is to be used for the expansion of B cells, the first agent immobilized on the multimerization reagent may be a binding reagent that specifically binds CD40 or CD137. In accordance with the disclosure given herein, in such embodiments the first binding reagent that specifically binds CD40 or CD137 may be selected from an anti- CD40-antibody, a divalent antibody nt of an anti-CD40 antibody, a monovalent antibody fragment of an anti-CD40-antibody, and a proteinaceous CD40 binding molecule with antibody-like binding properties or an anti-CD137—antibody, a divalent antibody fragment of an anti-CD137 antibody, a monovalent antibody fragment of an anti—CD137-antibody, a proteinaceous CD137 binding molecule with antibody-like binding properties, and CD40 ligand (CD154).

Also in accordance with the general disclosure of the present invention, in the erization reagent as described herein the binding sites Z1 and Z2 of the multimerization reagent can be identical. As described above, such a multimerization reagent may comprises an oligomer or a polymer of streptavidin, an oligomer or a polymer of avidin, an oligomer or a polymer of an analog of streptavidin that reversibly binds biotin, an oligomer or a polymer of an analog avidin that reversibly bind biotin, a reagent that ses at least two ing groups K, wherein the at least two chelating groups are capable of binding to a tion metal ion, thereby rendering the reagent capable of binding to an oligohistidine affinity tag, multimeric glutathione-S-transferase, eric calmodulin and a biotinylated r protein. id="p-98" id="p-98" id="p-98" id="p-98" id="p-98"

[0098] A novel composition provided herein that is e of expanding a population of cells may comprise (i) a first multimerization t, wherein the first multimerisation reagent is in soluble form and comprises at least one binding site Z] for the reversible binding of a first agent that provides a primary activation signal to the cells, wherein the first multimerization reagent has reversibly immobilized n (bound thereto) said first agent that provides a primary activation signal to the cells, wherein the first agent comprises at least one binding partner Cl, wherein the binding partner Cl is able ofreversibly binding to the at least one binding site Zl of the multimerization reagent, wherein the first agent is bound to the multimerization reagent via the reversible bond formed between the binding partner Cl and the binding site Zl , and (ii) a second multimerization reagent, n the second multimerization reagent is in soluble form and comprises at least one g site Z2 for the reversible binding of a second agent that stimulates an accessory molecule on the surface of the cells, wherein the multimerization reagent has reversibly immobilized thereon (bound thereto) said second agent that stimulates an accessory molecule on the surface of the cells, wherein the second agent comprises a binding partner C2, wherein the binding partner C2 is able of binding to the at least one binding site Z2 of the erization reagent, wherein the second agent is bound to the multimerization reagent via the bond formed between the binding partner C2 and the g site Z2. id="p-99" id="p-99" id="p-99" id="p-99" id="p-99"

[0099] Such a novel composition is, for example, the reaction mixture used in Example 13, in which two separate multimerization reagents were filnctionalized either with an (1CD3 Fab fragment alone or an (xCD28 Fab fragment alone. It is noted in this context, that such a composition was shown in Example 13 to have the same expansion efficiency as a single multimerization reagent on which both the first agent and the second agent are jointly lized. Thus, the combined use of two or more multimerization reagents being functionalized dually with only one type of reagent (for example, one first or one second agent) is functionally equivalent to using for the expansion one joint multimerization t which has immobilized thereon both a first agent and a second agent. In this context, it is also noted that a multimerization t of the present invention be functionalized with as many agents (for e, one, two, three, four or even more agents) that are intended to be used for the expansion of a ed cell population. A third or fourth agent may, for e, for example provide a us for the expansion of a desired subpopulation of cells. See in this context, for instance, e 13 in which a soluble multimerization reagents was reversibly onalized with three reagents, namely a (1CD3 Fab nt as first reagent, a (1CD28 Fab fragment as second reagent and a aCD8 Fab fragment as third reagent to enrich the subpopulation of CD8+ T cells in a sample of a population of CD3+ T cells (lymphocyte). By using such a combinations of agents that can all be reversibly immobilized on the same multimerization reagent, the present invention allows for the possibility to preferentially expand or selectively enrich any desired cell (sub)population from an sample that, for example, comprises a variety of different subpopulations. In this t, it is noted that it however also possible to use for this purpose use three different multimerization reagents, for example, a first multimerization reagent that is functionalized with only a (xCD3 Fab fragment, a second multimerisation reagent that is fianctionalized with a (1CD28 Fab fragment and a third multimerization reagent that is functionalized with a (1CD8 Fab fragment. Likewise, it is possible to use only two different multimerization reagents, a first multimerization reagent that is functionalized with only a aCD3 Fab fragment and a second multimerisation reagent that is fimctionalized with both a aCD28 Fab fragment and a (1CD8 Fab fragment. ingly, the present invention allows to design any kind ofwanted expansion reagent in a modular fashion.

The invention also provides an in vitro-method of serially expanding a tion of lymphocytes, wherein the population of lymphocytes comprises T cells. This method comprises contacting a sample comprising the T cell comprising population of lymphocytes with a multimerization reagent, wherein the multimerization reagent is in a soluble form and has reversibly immobilized thereon (i) a first agent that provides a primary activation signal to the T cells and (ii) a second agent which stimulates an accessory molecule on the surface of the T cells, wherein the erization reagent comprises at least one binding site Z1 for the reversible binding of the first agent, wherein the first agent ses at least one g partner Cl, wherein the binding partner Cl is able ofreversibly binding to the binding site Z1 of the multimerization reagent, wherein the first agent is bound to the multimerization reagent via the reversible bond formed between the binding partner C1 and the binding site Z1, wherein the multimerization reagent comprises at least one binding site Z2 for the ible binding of the second agent, wherein the second agent comprises at least one g partner C2, wherein the binding partner C2 is able of reversibly binding to the binding site Z2 of the multimerization reagent, wherein the first agent is bound to the multimerization reagent via the reversible bond formed between the binding partner C2 and the binding site Z2, wherein the first agent binds to a receptor molecule on the surface of the T cells, thereby providing a primary tion signal to the cells and thereby activating the T cells, wherein the second agent binds to the accessory molecule on the surface of the T cells, thereby stimulating the activated cells, the first agent and the second agent thereby together inducing the T cells to expand. id="p-101" id="p-101" id="p-101" id="p-101" id="p-101"

[00101] In this method contacting the sample that ns the population of lymphocytes that in turn contains the T cell population with the soluble multimerization reagent that has immobilized thereon the first and second agent results in specific binding of T cells to the multimerization reagent.

The contacting of the sample comprising the T cell comprising tion of lymphocytes with the multimerization reagent can be d out in a bioreactor such as a hollow-fiber ctor (e.g. hollow fiber bioreactor of the Quantum® cell ion system) or a plastic bag bioreactor (e.g. Cellbag® used in Xuri Cell Expansion System W25 from GE Healthcare).

This method further comprises contacting the population of lymphocytes ion mixture ning the T cells bound to the multimerization reagent Via the first agent and the second agent) with (i) a free first binding partner C1 or an analogue thereof e of disrupting the bond between the first binding partner C1 and the binding site Z1 and (ii) a free second binding partner C2 or an analogue thereof, capable of disrupting the bond between the second g partner C2 and the binding site Z2. By so doing the reversible bond between said binding partner C1 of the first agent and said binding sites Zl as well as the reversible bond between said binding partner C2 of the second agent and said binding site Z2 of said multimerization reagent is disrupted, thereby releasing in an eluate the T cells bound to the multimerization reagent Via the first agent and the second agent and stopping the expansion of the T cells.

] In this method the eluate (the on mixture in which the expansion reaction has been terminated by addition of the free first r(s) or analogue(s) thereof) that contains the ed T cell population may be exposed to chromatography on a le (first) stationary phase. The (first) stationary phase may be a gel ion matrix and/or an affinity chromatography matrix as bed in International patent application .

This gel filtration and/or affinity chromatography matrix comprises an affinity reagent, wherein the affinity reagent ses a binding site Z1 and/or Z2 specifically binding to the binding partner Cl and/or C2 comprised in the first agent or the second agent. By so doing the first agent, the second agent, the first binding partner C1 and/or the free second binding r C2 are immobilized on the stationary phase. In this method, the first stationary phase is fluidly connected to the bioreactor.

In one of the ments of this serial expansion the binding sites Z1 and Z2 of the multimerization agent are identical. In addition, a single multimerization agent may be used. When a soluble multimerization agent is used, the T cell population (or the expanded cell population in general) is separated from the soluble multimerization reagent. The separation/removal might be carried out using a second stationary phase. For this purpose, a mixture comprising the T cells and the soluble multimerization reagent are exposed, before or after being applied onto the first stationary phase described above, to chromatography on a suitable second stationary phase. This secondary stationary phase may be a gel filtration matrix and/or affinity chromatography matrix, wherein the gel filtration and/or affinity chromatography matrix comprises an y reagent. The affinity reagent comprised on the tography resin include a binding partner D that (specifically) binds to the binding site Z1 and/or binding site Z2, if present, of the multimerization reagent, thereby immobilizing the multimerization reagent on the stationary phase. If a streptavidin based multimerization agent is used and both first and second agents have a streptavidin binding peptide as binding partner C1 or C2, the binding partner D that is comprised in the affinity reagent of this second nary phase can be biotin. The soluble oligomer of streptavidin or of a streptavidin mutein that is used as multimerization reagent then binds to the biotin that is usually covalently coupled to a chromatography matrix such as biotin-sepharoseTM that is cially available.

In this method of serial expansion the first agent may stimulates a TCR/CD3 complex-associated signal in the T cells and the first agent may thus be a binding reagent that specifically binds CD3. In addition, the accessory molecule on the T cell may be CD28. In this case the second agent that binds the accessory molecule is a binding reagent that specifically binds CD28.

In this method of serial ion, the T cells may be ected either during or alter expansion e.g. with a T cell or (TCR) or a chimeric antigen or (CAR, also known as artificial T cell receptor). This transfection for the introduction of the gene of the desired receptor can be carried out with any suitable iral vector, for example. The genetically modified cell population can then be liberated from the initial stimulus (the CD3/CD28 stimulus, for example) and subsequently be stimulated with a second type of us e. g. via the de novo introduced receptor). This second type of stimulus may comprise an antigenic stimulus in form of a peptide/MHC molecule, the cognate (cross-linking) ligand of the genetically uced or (e.g. natural ligand of a CAR) or any ligand (such as an antibody) that ly binds within the framework of the new receptor (e.g. by recognizing constant regions within the receptor). Cf. in this respect, Cheadle et al, "Chimeric antigen receptors for T-cell based therapy" Methods Mol Biol. 2012; 907:645-66 or Barrett et a1., Chimeric Antigen Receptor Therapy for Cancer Annual Review of Medicine Vol. 65: 333-347 id="p-108" id="p-108" id="p-108" id="p-108" id="p-108"

[00108] In this method, the population of lymphocytes that comprises T cells can be a population of peripheral blood mononucleated cells (PBMC) or a population of enriched or purified T cells. The population of lymphocytes may, for example, be derived from whole blood, or from a non-mobilized apheresis product or a frozen tissue preparation.

In this method of serial expansion that is based on a soluble multimerization reagent, the first and second reagent as well as the multimerization reagent and all other reagents and cell populations can ise be used in the same manner as disclosed above for the method that makes use of reversible between the first or second agent and the multimerization reagent.

The invention is further directed to an arrangement of a bioreactor and a first stationary phase for chromatography. The bioreactor is suitable for the expansion of cells, and the nary phase is le for cell separation and removal of reagents. The first nary phase is a gel filtration matrix and/or affinity chromatography matrix, n the gel filtration and/or affinity chromatography matrix comprises an affinity reagent, wherein the affinity reagent comprises a binding site Zl specifically binding to a binding partner Cl comprised in a first agent and/or the affinity reagent comprises a binding site Z2 specifically binding to a g partner C2 comprised in a second agent. The first stationary phase is thereby being suitable of immobilizing thereon the first agent and/or the second agent, the first binding partner C1 and/or the free second binding partner C2. In addition the bioreactor and the stationary phase are fluidly connected. This arrangement can be used in the serial expansion as explained above and can be integrated into known cell expansion systems such as the Quantum® cell expansion system) or the Xuri Cell Expansion System W25. id="p-111" id="p-111" id="p-111" id="p-111" id="p-111"

[00111] In this arrangement the first stationary phase is either comprised in a chromatography column or is a planar stationary phase. The arrangement may further comprises a second stationary phase which is fluidly connected to the first nary phase.

The ary stationary phase may be a gel filtration matrix and/or affinity chromatography matrix, wherein the gel filtration and/or affinity chromatography matrix comprises an affinity reagent. This affinity reagent may comprise a binding partner D that (specifically) binds to the binding site Zl of the multimerization reagent, thereby being suitable of immobilizing the erization reagent on the stationary phase.

The invention is further directed to an apparatus for purification and expansion of a population of cells, the apparatus comprising at least one arrangement of a bioreactor and a first stationary phase or a second stationary phase for chromatography as defined above.

The tus may further comprise a ity of arrangements of a bioreactor and a stationary phase being fluidly connected in series.

The tus may se a sample inlet being fluidly connected to the bioreactor of the arrangement of a bioreactor and the stationary phase for chromatography. The apparatus may also comprise a sample outlet for purified and expanded target cells, the sample outlet being fluidly ted to the stationary phase of the last of the at least one arrangement of a bioreactor and the stationary phase for chromatography.

Finally, the apparatus may be ed as a functionally closed system.

As one of ordinary skill in the art will readily appreciate from the disclosure of the t invention, other compositions of matter, means, uses, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding exemplary embodiments described herein may likewise be utilized according to the present invention.

Experimental Examples Example 1: Stimulation/expansion of CD3+ T responder cells with CD28 Fab nts that were reversibly immobilized on beads coated with the streptavidin mutein Strep-tactin®. 300.000 CD3+CD62L-responder T cells (Tresp, isolated by serial magnetic enrichment from a non-mobilized donor sis product) were labeled with 3uM CFSE and stimulated with Sul of a 15111 preparation of actin® beads (10 mg magnetic particles/ml, loaded with 35 ug Streptactin®/mg beads) either loaded with 0.5ug orCD3 Fab fragment alone, 0.5ug dCD28 Fab nt alone or a e of 0.5 ug orCD3 Fab fragment and 0.5ug dCD28 Fab.

The (xCD3 Fab fragment used was derived from the CD3 binding monoclonal antibody produced by the hybridoma cell line OKT3. The hybridoma cell line OKT3 and the OKT3 antibody are described in US Patent 4,361,549, the cell line has been deposited under accession number ATCC® CRL-8001TM). The CD28 Fab used was derived from the monoclonal anti-human CD28 antibody CD283 (Vanhove et a1, BLOOD, 15 July 2003, Vol. 102, No. 2, pages 564-570). The nucleotide sequence of the variable s of this antibody CD283 has been deposited in GenBank in the form of a synthetic single chain Fv uct anti-human CD28 antibody scFv28.3 under k accession number AF451974.1). id="p-119" id="p-119" id="p-119" id="p-119" id="p-119"

[00119] Both Fab fragments were recombinantly produced in E. 0012' as described in International patent applications W02013/011011 and carrying as constant domains (CH1 and Ckappa) an IgGl consensus sequence. The heavy chain of both Fab fragments was carboxy-terminally fused with a sequential arrangement of two avidin binding modules (SAWSHPQFEK(GGGS)2GGSAWSHPQFEK, (SEQ ID NO: 07)), that is commercially available as "Twin-Strep-tag® from IBA GmbH, Gottingen, Germany). The orCD3 Fab fragment was used as first agent with the streptavidin binding peptide serving as binding partner C 1 and the (1CD28 Fab fragment was used as second agent with the streptavidin binding peptide g as binding partner C2. The (tetrameric) streptavidin mutein "Strep—tactin® serves as multimerization reagent on which both Fab fragments were ibly immobilized.

In the expansion experiment, Tresp cells stimulated with blank beads (no Fab) served as negative control. Tresp cells were seeded in triplets in 48-well plates along with 300.000 CD3 cells autologous feeder cells (irradiated with 30Gy) in 3m1 complete cell culture medium (RPMI (Gibco) supplemented with 10% (v/v) fetal calf serum, L-glutamine, b- mercapto ethanol, HEPES, penicillin, streptomycine and ycine) supplemented with IOU/ml interleukin 2 (IL-2). The cells were ted at 37°C without media exchange and analyzed alter 4 days by FACS analysis. FACS staining and analysis was done after 10min incubation with lOOuM D-biotin. One representative plot for each condition is shown in Fig. 4. Plots show live CD3+ cells that were stained with propidium iodide (PI) for live/dead discrimination. Fig. 4a is a histogram showing size-distribution (forward scatter) of ated cells. Fig. 4a shows that a specific cell population of Tresp cells was stimulated and expanded (increase in umber compared to the ulated "beads only" control) when incubated in the presence of beads on which a mixture of 0.5ug (1CD3 Fab fragment and 0.5ug uCD28 Fab was immobilized, after being stimulated in vitro with uCD3/uCD28 Fab fragments that were ibly immobilized on beads coated with the streptavidin mutein Strep-tactin®. Fig. 4B s histograms of the dilution of the proliferation dye CFSE representing the degree of proliferation according to the number of cells per cell division (indicated on top of Fig. 4B, 0 represents undivided cells; 5 represents cells that have gone through at least 5 divisions). It can be seen from Fig. 43 that the population of T cells stimulated with the beads on which a mixture of 0.5ug uCD3 Fab fragment and 0.5ug uCD28 Fab was immobilized have mostly gone through three cell divisions and represent a more uniform eration pattern than with a single stimulus alone (small number of cells within the undivided peak "0"). The increased absolute amount of proliferation (more cells have proliferated uniformly after 4d ation with uCD3 and uCD28 fianctionalized beads) is also represented by a more intense consumption of media as ed by a indicator color change to yellow in Fig. 4C.

Example 2: Analysis of the differential intracellular calcium mobilization in Jurkat cells ime low-cytometric analysis of the differential intracellular calcium mobilization induced in Jurkat cells that are either labeled with the aCD3 antibody clone OKT3 or with Fab fragments of OKT3 being multimerized with Strep-tactin® was ed here. id="p-122" id="p-122" id="p-122" id="p-122" id="p-122"

[00122] For this purpose, Jurkat cells were loaded with the calcium-sensitive dye lndo-l-AM and calcium release was triggered by injection of either (xCD3 monoclonal antibody OKT3 (produced by the hybridoma cell line OKT3, see above, black squares) or (1CD3 Fab fragments ed from the parental cell line OKT3) that were multimerized by reversible binding of its streptavidin binding peptide to e Strep-Tactin fluorescently conjugated with phycoerythrin. In the case of the intact eric OKT3 Fab-Strep-Tactin complexes, the calcium release was triggered over an identical time period as with the al antibody clone (dark grey triangles). Activation of cells could be completely avoided by injection of D-biotin treated, ssociated Fab-Strep-Tactin complexes (light grey circles) identical to injection of the PBS negative control (inverted white triangles). Application of ionomycine served as ve control for calcium influx. Time-resolved changes in intracellular Ca2+ concentration were monitored by flow-cytometry based on the change in FL6/FL7 ratio. It can be seen from Fig. 5A that both the parental antibody OKT3 as well as the erized monovalent Fab fragment of OKT3 effected m e, meaning that the multimerized monovalent Fab fragment of OKT3 is essentially as fiinctional as the parental antibody. Notably, the multimeric OKT3 Fab fragment was not able to trigger calcium release if biotin was added to Strep-tactin on which the OKT3 Fab fragment was immobilized prior to the addition of the Streptactin—OKT3 Fab fragment. In this case, the biotin disrupted the reversible bond formed n Strep-tactin as multimerization agent and the OKT3 Fab fragment. The monovalent Fab fragment was therefore ced from the multimerisation agent and after dissociation was not able to trigger m release by g to CD3 of the Jurkat cells.

In the experiments shown in Fig. 5B indo-l-AM-labeled Jurkat cells were activated by OKT3 derived aCD3 rep-Tactin—complexes as described in Fig. 5a.

Injection of intact (upper graph) or pre-dissociated complexes (lower graph) served as positive or negative controls respectively. In addition, stimulation of cells with intact Fab-Strep Tactin— complexes followed by uent injection of D-biotin (near the peak activation at t=14OS) resulted in abrupt disruption of uCD3 Fab-multimer signaling (middle graph). Injection of ionomycine into the pre—dissociated Fab complex group served as positive control. Data are representative of three different experiments. Importantly, Fig. 5B shows that the addition of D-biotin to the sample rapidly displaces the Fab fragment from the Strep-tactin multimerization agent, thereby effectively terminating the calcium release even under ongoing calcium stimulation and demonstrating that the dissociated OKT3 Fab fragment is not any longer biologically . Likewise, the multimeric OKT3 Fab fragment was also not able to r calcium release when biotin was added to the Strep-tactin—OKT3 Fab fragment multimer prior to the addition of the Streptactin—OKT3 Fab sample to the Jurkat cells.

Example 3: Reversible staining of cells by CD3 Fab-multimers This Example examines the reversible staining of cells by CD3 Fab- multimers. Freshly isolated PBMCs were stained with either the dCD3 monoclonal antibody clone OKT3 (left dot plot, parental clone for the Fab-multimers) or cognate phycoerythrine (PE)-labeled OKT3 Fab-multimers and analyzed either before (second left column) or after treatment with D-biotin (middle column). Remaining Fab monomers were then detected after subsequent washing steps using fresh PE-labeled Strep-Tactin® d right column).

Secondary Fab-multimer staining of reversibly stained cells served as control (right column).

Only live CD3 cells which are negative in ng with propidium iodide (PI) for ead discrimination are shown in Fig. 6. Numbers in dot plots indicate the percentage of cells within gates. This experiment shows that the staining of CD3+ PBMCs with an anti-CD3 Fab fragment multimerized with Streptactin as ization reagent is fully reversible by addition of D-biotin and that the lent Fab fragment alone does not bind to the CD3 molecule t on PBMCS. e 4: Reversible isolation of cells by CD28 Fab-multimers id="p-125" id="p-125" id="p-125" id="p-125" id="p-125"

[00125] This Example shows the isolation of cells by reversible binding of anti- CD28 Fab fragments multimerized with Strep-Tactin® magnetic particles (the magnetic particles are available from IBA GmbH Gottingen, Germany). The Fab fragments derived from the antibody CD283 described in e 1 above were used for this purpose. CD28+ cells were ed/isolation by ltimer magnetic cell selection from freshly isolated PMBCs as essentially described in International Patent Application W02013/011011. Before selection cells were control stained with either the cognate fluorescent (xCD28—mu1timers (left dot plot) or with an antibody directed against the irnmunoglobulin kappa light chain d left dot plot, oc-Ig kappa mAb) as a control staining. After selection, CD28+ cells were treated with D-biotin and subsequently washed to remove magnetic beads and Fab-monomers.

Liberated CD28+ cells were subsequently (re-) stained either with CD28 Fab-multimers (second right dot plot) or with the a—ngappa mAb (right dot plot) to detect potentially ing Fab-monomers. Only live (Plnegafive) CD3+ cells are shown. Numbers in dot plots te the percentage of cells within gates. Fig. 7 shows that CD28+ cells can be isolated from PMBC using such multimerized anti-CD28 Fab nt and that all isolation reagents including the anti CD28 Fab—monomers can be removed after selection.

Example 5: Stimulation/expansion of CD3+ T responder cells with aCD3/aCD28 Fab fragments that were reversibly immobilized on soluble Strep-tactin In this example CD3+ T responder cells (isolated by magnetic selection from a sample of fresh PBMCs obtained from a Ficoll nt) were expanded after in vitro stimulation with aCD3/(xCD28 Fab fragments that were reversibly immobilized on soluble oligomeric Strep-tactin® acting as a soluble multimerization t. The oligomeric Strep- tactin® was obtained by polymerizing Strep-tactin® with sulfo SMCC (sulfosuccinimidyl 4- (N-maleimidomethy1)cyclohexane-l-carboxylate, product # 22122 Thermo Scientific) and iminothiolan (product # 26101 Thermo Scientific) according to the protocol of the manufacturer o Scientific). The oligomeric streptavidin were separated from monomeric (unreacted) and dimeric streptavidin mutein by size exclusion tography and the so obtained fraction of the oligomeric avidin mutein (n2 3) was used as soluble multimerization reagent.

For the in vitro expansion, 300.000 CD3+ responder T cells (Tresp) were labeled with 2uM yfluorescein succinimidyl ester (CFSE) and stimulated with varying amounts of a preparation of soluble Strep-tactin® oligomers on which a combination of the above described (XCD3 OKT3 Fab fragment and the (xCD28 Fab fragment of the antibody 28.3 (both carrying the above-mentioned Twin—Strep-tag® as streptavidin binding peptide at the heavy chain) were immobilized. ("lx" corresponds to 3 ug multimerized Streptactin fiinctionalized with 0.5ug of the orCD3- and 0.5ug (1CD28 monomeric Fab fragment, the s "0.5x", "2x" and "5x" indicate the respective n-fold amount of "1x"). Tresp cells either left unstimulated or were ated with blank Strep-tactin multimers (no Fab) served as negative controls. Tresp cells were seeded in duplicates in 48-well plates along with 0 CD3 negative gous feeder cells (irradiated with 30Gy) in lml cell culture medium supplemented with 20U/m1 IL-2. Cells were incubated at 37°C without media exchange and proliferation was analyzed according to CFSE dilution after 5 days by FACS is. Fig. 8A shows the increase in the size distribution of proliferating cells after 5 days in culture compared to the negative controls. Fig. 8B shows that CD3+ Tresp cells were properly stimulated and proliferated vigorously when incubated with soluble oligomeric Strep-tactin® (as ed to solid actin magnetic particles in Fig.4) on which a mixture of aCD3 Fab and (1CD28 Fab fragments were immobilized. The results in Fig. 8a and 8b indicate that under these in vitro conditions most of the CD3+ T responder cells divided (2 to 5 cell divisions) afier ment of the surface CD28 and TCR/CD3 x with the uCD3 and (1CD28 Fab fragments that were reversibly immobilized on soluble Strep—tactin® oligomers. After in vitro expansion the soluble Fab-Strep—Tactin stimulation reagents were dissociated and removed after D-biotin treatment. The dissociation and removal of monomeric Fab fragments was flow- cytometrically analyzed by restaining cells with phycoerythrine label Strep-Tactin®) (ST-PE).

A representative histogram (dark grey histogram) is shown compared to the appropriate ST—PE only negative control (light gray histogram). It can be seen from Fig. 8C that both Fab nts had completely dissociated and were entirely d from the expanded cells. Fig. 8D shows the absolute number of live (trypan blue negative) cells after 5 days. The number was d using a Neubauer counting chamber and plotted t the respective stimulation condition. Median cell numbers are shown in Fig. 8D; error bars indicate standard deviation (SD). Fig. 8D shows that all which mixtures of (xCD3 Fab fragments and dCD28 Fab fragments that were immobilized on a soluble Strep-tactin multimerization reagent were equally effective in expanding the CD3+ cells and resulted in an approx. 4-fold increase of absolute cell numbers.

Example 6: Kinetics of proliferation of purified CD4+ and CD8+ T responder cells ated in vitro with reversible aCD3/aCD28 Fab-Streptamer multimers without medium exchange In this example the ion kinetics of proliferation of purified CD4+ and CD8+ T der cells ) that were stimulated in vitro with dCD3/0tCD28 Fab fragments that were reversibly immobilized soluble eric streptavidin muteins were examined. For this purpose, e oligomeric Strep-tactin® mutein of two different sizes served as soluble multimerization reagent. The first kind of oligomeric Strep-tactin® was the fraction of the oligomeric streptavidin mutein (n2 3) obtained in Example 5 (also ed herein as "conventional Streptactin® backbone", illustrated by the le symbol with the tip on top in Fig. 13). The second kind of this oligomeric streptavidin mutein used as soluble multimerization reagent was an oligomeric streptavidin mutein (n2 3) that was reacted with biotinylated human serum albumin (also referred herein as "large Streptactin® ne).

In this e 500.000 purified CD4+ or CD8+ responder T cells (Tresp) were separately stimulated with these two different Streptamer ers as explained above, i.e. with either the Streptactin backbone of Example 5 (using a solution with a concentration of 1mg oligomeric streptavidin mutein/ml)) or with the large Streptactin backbones (0.1mg/ml). 3 ul of the both different backbones were either loaded with a ation of 0.5ug of the dCD3 and 0.5ug dCD28 Fab used in the earlier Examples that carried a streptavidin binding e SAWSHPQFEK(GGGS)2GGSAWSHPQFEK (SEQ ID NO: 07) at the C-terminus of the heavy chain of the Fab fragment. In addition, 4.5 ul of the conventional Streptactin backbone was loaded with 0.5ug uCD3 Fab fragment, 0.5 ug (xCD8 Fab fragment (IBA GmbH Gottingen, that also carries at the C—terminus of the Fab fragment the streptaVidin binding peptide SAWSHPQFEK(GGGS)2GGSAWSHPQFEK (SEQ ID NO: 07) and 0.5ug uCD28 Fab fragment. ted (unstimulated) Tresp cells served as negative control and Tresp cells stimulated with commercially available Dynabeads (beads on which (1CD3 and 0LCD28 monoclonal dies are irreversible lized) as positive control. Tresp cells were seeded in duplicates in 48-well plates in 1m1 cell culture medium (RPMI 1640 (Gibco) supplemented with 10% (V/V fetal calf serum, 0.025% (w/V) L-glutamine, 0.025% (w/V) L- arginine, 0.1% (w/V) HEPES, 0.001% (w/V) gentamycine, 0.002% (w/V) streptomycine, 0.002% (w/V) peniciline) supplemented with 30U/ml IL-2. Cells were incubated at 37°C without media exchange and cell count was analyzed after 1, 3 and 6 days. In the experiments of Fig. 13 the expansion was d out without medium exchange. The results for the CD4+ T responder cells are shown in A, the results for the CD8+ T responder cells are shown in Fig. 133, with the graphs representing degree of proliferation ing to the number of cells harvested per time point for CD4+ Tresp (Fig. 13A) and for CD8+ Tresp in Fig.13B.

As can be seen from Fig. 13A the "smaller" soluble multimerization t on which uCD3 and uCD28 Fab fragments were reversibly lized provided for the same amount of expansion of CD4+ T cells as Dynabeads (which are so far the standard reagent for the expansion of T cells), while the "larger" oligomeric soluble streptactin provided for even better expansion compared to Dynabead. This improvement might be caused by the soluble "larger oligomeric multimerization reagent" being able to bind to more T cells at the same time than the "smaller" soluble oligomer, thereby being able to stimulate more CD4+ T cells than the er" oligomer.

As evident from Fig. 13B, using the soluble multimerization reagents of the present invention CD8+ T cells could be expanded within the first 3 days at least as ently as with Dynabeads. Notably, in this time period, the expansion ment that used a soluble multimerization reagent that in addition to uCD3 and uCD28 Fab fragments (as first and second agent) carried reversibly immobilized thereon 0LCD8 Fab fragment, showed the best degree of expansion under these culturing conditions. This indicates that it is le by using a stimulus that is specific for a particular sub-population of cells (here the uCDS Fab fragment) to increase or modulate the selectivity of the expansion, thereby being able to obtain larger amounts of a desired cell (sub)—population.

Thus, summarizing the above, Example 6 shows that the functionality of the soluble multimerization reagent used in the present invention in terms of triggering expansion of T cells is comparable to the current standard methodology of using Dynabeads for this purpose. r, since the stimulation can be controlled (and terminated, if wanted) by adding a competitor such as biotin in the case of a streptavidin based ible interaction between the first and second agent and the erization reagent, the present invention provides a significant advantage over the Dynabeads technology since the expansion conditions can be optimized (it would for example be possible to stop the stimulation in the experiment of Fig.13B after 3 days). In addition, since the soluble multimerization reagent can be easily removed from the reaction (for example, by immobilizing the reagent on a ylated column after the expansion reaction), the expansion method of the invention can be carried out and automated in closed systems that are, for e, needed for GMP production of cells for therapeutic es, t having to deal with the l of beads such as Dynabeads.

Example 7: Kinetics of proliferation of purified CD4+ and CD8+ T responder cells stimulated in vitro with reversible aCD3/aCD28 Fab-Streptamer multimers with medium exchange id="p-133" id="p-133" id="p-133" id="p-133" id="p-133"

[00133] Also in this example the expansion kinetics of proliferation of purified CD4+ and CD8+ T responder cells (Tresp) that were stimulated in vitro with uCD3/uCD28 Fab fragments that were reversibly immobilized on soluble oligomeric streptavidin muteins were examined. For this e, soluble oligomeric Strep-tactin® mutein of two different sizes served as soluble multimerization reagent. The first kind of oligomeric Strep-tactin® was the fraction of the oligomeric streptavidin mutein (n2 3) ed in Example 5 (also referred herein as ntional Streptactin® backbone", illustrated by the triangle symbol with the tip down in Fig. 13). The second kind of this oligomeric streptavidin mutein used as soluble multimerization reagent was ed by reacting the oligomeric Strep—tactin (n2 3) obtained in Example 5 with biotinylated human serum n. This e oligomeric multimerization reagent is also referred herein as "large Streptactin® backbone.

In this example, 400.000 purified CD4+ or CD8+ responder T cells (Tresp) were separately stimulated with these two different Streptamer multimers as explained above, i.e. with either the Streptactin backbone of Example 5 (1.0 mg/ml) or with the large Streptactin backbones (0.1mg/ml). 3ul of both the different backbones were either loaded with a combination of 0.5ug 0iCD3 and 0.5ug 0iCD28 Fab fragments described above. In addition, 4.5 ul of the Streptactin backbone of Example 5 was loaded with 0.5 ug 0LCD3, 0.5ug (1CD8 Fab and 0.5ug 0iCD28 Fab fragment as described above. Untreated (unstimulated) Tresp cells served as negative control and Tresp cells stimulated with Dynabeads (on which (1CD3 and uCD28 monoclonal antibodies are irreversible immobilized) as positive control. Tresp cells were seeded in ates in l plates in lml cell culture medium supplemented with 30U/ml IL-2. Cells were ted at 37°C with media exchange on day 3 and cell count was analyzed after 1, 3 and 6 days. The s for the CD4+ T responder cells are shown in A, the results for the CD8+ T responder cells are shown in Fig. 143, with the graphs representing degree of proliferation according to the number of cells harvested per time point for CD4+ Tresp (Fig. 14A) and for CD8+ Tresp in Fig.14B. id="p-135" id="p-135" id="p-135" id="p-135" id="p-135"

[00135] As can be seen from Fig. 14A the soluble multimerization reagents of the present invention on which (1CD3 and (xCD28 Fab fragments were reversibly immobilized ed for better expansion of CD4+ T cells than Dynabeads.

As t from Fig. 14B, using the soluble multimerization reagents of the present invention CD8+ T cells could be ed within the first 6 days at least as efficiently as with Dynabeads. Notably, in this time period, the ion experiment that used the larger soluble multimerization reagent that carried (1CD3 and (1CD28 Fab fragments (as first and second agent) showed the best degree of expansion under these culturing conditions. This might again be caused by the soluble "larger oligomeric multimerization reagent" being able to bind to more T cells at the same time than the "smaller" soluble oligomer, thereby being able to stimulate more CD4+ T cells than the "smaller" er.

Example 8: Expansion kinetics of purified CD4+ and CD8+ T cell cultures with or without medium exchange In this Example the combined data from Examples 6 and 7 were normalized on input cell number for the er" soluble multimerization reagent and positive and negative l. No normalization data was obtained on the "larger" multimerization reagent. As explained in Examples 6 and 7, 400.000 to 500.000 CD4+ or CD8+ der T cells (Tresp) were stimulated with 3 ul of a preparation of Streptactin multimers (lmg/ml; on which 0.5ug (xCD3 Fab fragment and 0.5pg aCD28 Fab fragment were immobilized. Untreated (unstimulated) Tresp cells served as negative control and Tresp cells stimulated with ads as positive control. Tresp cells were seeded in duplicates in 48-well plates in lml cell culture medium supplemented with 30U/ml lL—2. Tresp cells were seeded in duplicates in 48-well plates in lml cell culture medium supplemented with 30U/ml IL-2. Cells were ted at 37°C with media exchange ght lines in Fig. 15) or without media exchange d lines in Fig. 15) on day 3 and cell count was analyzed after 1, 3 and 6 days. As evident from the normalized data of Fig. 15A, the "smaller" soluble erization t on which (xCD3 and orCD28 Fab fragments were reversibly lized yielded an about 2.5 fold expansion of CD4+ T cells, while the expansion using Dynabeads yielded an about 1.8 fold expansion rate. Thus, the use of a soluble multimerization reagent of the invention even provides for an improvement in the expansion of CD4+ T cells over Dynabeads. Similarly, Fig. ISB, confirms that using the soluble erization reagents of the present invention CD8+ T cells could be expanded within the first 3 days at least as efficiently as with ads.

Example 9: Early cluster formation after activation of purified CD4+ and CD8+ T responder cells stimulated in Vitro with reversible aCD3/aCD28 Fab-Streptamer multimers id="p-138" id="p-138" id="p-138" id="p-138" id="p-138"

[00138] In this Example, 400.000 CD4+ or CD8+ responder T cells (Tresp) were stimulated with 3 pl of a preparation of oligomeric Streptactin multimerization reagent (1mg/ml) loaded with a combination of 0.5ng aCD3— and 0.5ug (xCD28 Fab. Untreated (unstimulated) Tresp cells served as negative control and Tresp cells stimulated with Dynabeads as positive l. Tresp cells were seeded in duplicates in 48-well plates in lml cell culture medium supplemented with 30U/ml IL—2. Cells were incubated at 37°C and microscopically analyzed after 1 and 2 days. Stimulation of CD4+ Tresp (Fig. 16A) and CD8+ Tresp (Fig. 163) are shown for Dynabeads e row) and Streptamer multimers (lower row) respectively. The photographs represent degree of r formation: For better Visibility exemplary clusters are indicated by circles for the stimulation with soluble streptavidin mutein oligomers in Fig. 16A and Fig. 168. Clusters within the Dynabead stimulation are readily visibly by accumulation of dark stimulatory particles. As evident, both for CD4+ and CD8+ T cells early clusters formed when using the expansion method of the invention that employs a soluble oligomeric multimerization reagent.

Example 10: Expansion kinetics & phenotype of polyclonal activated/expanded bulk CD3+ central memory T cells (Tcm) In this Example, 500.000 CD3+CD62L+CD45RA- responder Tcm cells ) were ated with 3 ul of a preparation of the soluble oligomeric Streptactin of Example 5 (1mg/ml) that was either loaded with a combination of 0.5ug dCD3 and 0.5ug uCD28 Fab. rmore, 4.5 ul of a preparation of Streptactin multimers loaded with 0.5ug (xCD3, 0.5ug dCD8 Fab and 0.5ug dCD28 Fab was used as an additional ation condition. Untreated (unstimulated) Tresp cells served as negative control and Tresp cells stimulated with Dynabeads (on which orCD3 and dCD28 monoclonal antibodies are irreversible immobilized) as positive control. Tresp cells were seeded in 48-well plates in 1ml cell culture medium supplemented with 30U/ml IL-2 only or 30U/m11L-2 and Sng/ml IL-15. Cells were incubated at 37°C with media exchange every 3 days and cell count was ed after 7 and 14 days.

Graphs represent degree of proliferation according to the number of cells harvested per time point, in Fig. 17A only IL-Z supplemented media and in Fig.17B IL-2 and IL-15 supplemented media. As can be seen from both Fig.17A and Fig. 17B, the soluble multimerization reagent that has reversibly bound n CD3 Fab nt and uCD28 Fab fragment yields better cell expansion than the Dynabeads. As further shown by the flow-cytometric analysis of CD62L and CD127 surface expression after 14 days of e in variable cytokine milieus of Fig. 17C, the experimental ches using soluble multimerization reagents of the present invention retain, under both conditions chosen here, a higher t of CD127-expressing long-lived memory T cells than expansion with Dynabeads. This illustrates a further advantage ofthe methods of the present invention.

Example 11: Selective Antigen-specific expansion of Tcm responder cells out of bulk CD3+ central memory T cells ics & phenotype) In this Example, the kinetics and the phenotype of selective Antigen specific (Ag-specific) expansion out of purified CD3+CD62L+CD45RA- Tcm responder cells was examined.

] In more detail, CD3+CD62L+CD45RA— Tcm responder cells were stimulated in vitro with both a peptide:MHC molecule complex (that acts as first agent that provides a primary activation signal to the cells) and an orCD28 Fab fragment (that acts as second reagent that stimulates an accessory molecule on the surface of the cells). Both the complex of antigen Specific peptide with the MHC molecule and the uCD28 Fab fragment were reversibly immobilized on the soluble oligomeric streptavidin mutein (with n2 3) described in Example . The peptide that was used for the antigen specific expansion was the peptide CRVLCCYVL (SEQ ID NO: 06), amino acids 7 of the ate-early 1 protein (described in Ameres et al, PLOS Pathogens, May 2013, vol. 9, issue 5, e1003383) representing an HLA— l epitope that is specific for cytomegalovirus (CMV). The MHC I molecule that presents the peptide carries at the C-terminus of the or chain (heavy chain) the streptavidin binding peptide (SAWSHPQFEK(GGGS)2GGSAWSHPQFEK, (SEQ ID NO: 07) that is commercially available as "Twin-Strep-tag®" from IBA GmbH, gen, Germany).

For this purpose, 500.000 CD3+CD62L+CD45RA- responder Tcm cells (Tresp) were stimulated Ag-specifically using 3 ul of a preparation of soluble oligomeric Streptactin erization reagent fianctionalized with 0.5 ug of the peptide:MHC class I complexes equipped with the streptavidin binding peptide and with 0.5ug of the uCD28 Fab described above. As an alternative, 4.5 ul of a of preparation of the Streptactin multimerization reagent were loaded with 0.5ug ofthese ezMHC class I xes, 0.5ug CD8 uFab and 0.5 ug (1CD28 Fab. For comparison, onal stimulation was performed, using 31.11 of a preparation of Streptactin multimerization reagent (lmg/ml) either loaded with a combination of 0.5ug uCD3 Fab and 0.5ug aCD28 Fab. Again as the alternative stimulation condition described above, 4.5ul of a preparation of Streptactin multimerization reagent reversibly loaded with 0.5 ug orCD3 Fab, 0.5ug orCD8 Fab and 0.5ug uCD28 Fab was used. Untreated (unstimulated) Tresp cells served as negative control and Tresp cells stimulated polyclonal with Dynabeads (beads on which uCD3 and (1CD28 monoclonal antibodies are irreversible immobilized) as positive control. Tresp cells were seeded in 48—well plates in lml cell culture medium supplemented with 30U/ml IL-2 and 5ng/ml IL-lS. Cells were ted at 37°C with media exchange every 3 days and cell count was analyzed after 7 and 14 days. The exemplary flow-cytometric analysis for the fraction of Ag-specific cells that was ated/expanded via the soluble strept-tactin oligomer on which the peptidezMHC—I complex for an /IE-l e (for CMV) was immobilized (Fig. 18A) show that these antigen-specific T cells were specifically expanded. The graphs of Fig. 18B to Fig. 18E (that represent the degree of expansion of ct Ag—specificities according to the number of peptide:MHCI multimer- positive cells harvested per time point in analogy to the expansion experiment shown in Fig.18A) show that, the multerimerization reagent that uses the respective complex of the Ag- c peptide and MHC 1 molecule provided for the highest number of expanded cells (ranging from an twentyfold increase in the number of cells for the Ag-specific cells that recognize the pp65 epitope ofCMV (amino acids 341-350 (QYDPVAALF, (SEQ ID NO: 08)) restricted by HLA-A2402) (see Fig. ISB) to an 98 fold increase in the number of Ag-specific cells that recognize the HLA-B7/IE-1309_317 epitope (CRVLCCYVL (SEQ ID NO: 06)) of CMV (see Fig. 18E), thereby showing that the expansion method of the present ion is fully applicable to the expansion of Ag-specific cells. Finally, the exemplary flow-cytometric analysis of CD62L and CD127 surface expression after 14 days of e for HLA- B7/Hexon5 epitope (for adenovirus) shown in Fig. 18F r confirms that experimental approaches using the soluble multimerization ts of the present invention retain a higher content of expressing long-lived memory T cells in polyclonal and cific stimulatory ions.

Example 12: Selective Ag—specific expansion kinetics & phenotype of bulk central memory T cells This Example examines the kinetics of selective Ag-specific expansion out of purified CD3+CD62L+CD45RA—Tcm responder cells that were stimulated in vitro with a) antigen specific peptide MHC I complexes and b) aCD28 Fab fragments that were reversibly immobilized as first and second agent on soluble oligomeric streptavidin muteins.

For this purpose 500.000 CD3+CD62L+CD45RA- responder Tcm cells (Tresp) were stimulated cifically using 3u1 of a preparation of Streptactin multimerization reagent fimctionalized with 0.5ug peptidezMHC class I complexes equipped with a streptavidin g peptide (the specific peptide represents amino acids 114-124 (CPYSGTAYNSL, SEQ ID NO: 10) of the Hexon 5 protein of adenovirus ) restricted by HLA-B07) and 0.5ug uCD28 Fab. As an alternative, 4.5 ul of a preparation of Streptactin multimerization reagent loaded with 0.5 ug this peptide2MHC class I complex, 0.5ug (1CD8 Fab and 0.5ug (XCD28 Fab. For comparison, polyclonal stimulation was performed, using 3 ul of a preparation of Streptactin multimerization reagent l) either loaded with a combination of 0.5 ug (1CD3 Fab and 0.5ug uCD28 Fab. Again as the alternative stimulation condition described above, 4.5ul of a preparation of Streptactin multimers loaded with 0.5ug uCD3 Fab, 0.5ug uCD8 Fab and 0.5ug uCD28 Fab was used. Untreated (unstimulated) Tresp cells served as negative control and Tresp cells ated polyclonal with Dynabeads as positive control. Tresp cells were seeded in 48—well plates in lml cell culture medium supplemented with 30U/ml IL-2 and Sng/ml IL-lS. Cells were incubated at 37°C with media exchange every 3 days and cell count was ed after 7 and 14 days. The pictures shown in Fig. 19 represent degree of r formation on day 5, exemplary Ag-specific stimulation is illustrated for the HLA-B7/Hexon 5 e of adenovirus. As can be seen from Fig. 19, such adenovirus antigen specific cells could be specifically expanded from the al 62L+CD45RA-Tcm responder population.

Example 13: Yield and phenotype of expanded CD8+ T cells — size variation of soluble multimerization reagent and addition of uCDS-Fab addition for stimulation In this Example, the expansion of d CD8+ T responder cells stimulated in vitro with (XCD3/(XCD28 Fab fragments that were reversibly immobilized soluble oligomeric streptavidin muteins were examined. In addition, the effect of adding aCDS-Fab to the erization reagent for increasing the specificity of the expansion for CD8+ T cells was examined.

For this purpose, 300.000 purified CD8+ responder T cells (Tresp) were separately stimulated with two different Streptactin based multimerization reagents, namely either the small oligomeric Streptactin multimerization reagent of Example 5 (lmg/ml) or the larger Streptactin ers described above (0.1mg/ml). 3ul of both different multimerization reagent (backbones) were either loaded with a combination of the 0.5ug aCD3 and 0.5 ug (xCD28 Fab fragments described above. In addition, 4.5 ul of the smaller Streptactin multimerization reagent (backbone) was loaded with 0.5 ug (1CD3, 0.5 ug aCD8 Fab and 0.5 ug (1CD28 Fab fragments bed above. Furthermore 3ul of the "smaller" Streptactin multimerization reagent one) only fianctionalized with 0.5ug (xCD3 Fab fragment alone or 0.5 ug (1CD28 Fab fragment alone was used. Unstimulated Tresp cells served as negative control and Tresp stimulated with ads served as positive control. Tresp cells were seeded in duplicates in 48—well plates in lml cell culture medium supplemented with 30U/ml IL-2. Cells were incubated at 37°C with media exchange after 3 days and analyzed afier 6 days. Fig. 20A depicts the degree of proliferation according to the number of cells harvested at day 6 compared to the negative controls and normalized to the ve control. Fig. 20A shows that the expansion of the CD8+ T cells using the soluble multimerization reagents of the invention result in higher yields of the CD8+ T cells than expansion using dynabeads. The FACS analysis of CD8 e expression (Fig.20B) and CD45RO surface expression (Fig. 20C) after cell culture shows that the same phenotype of CD8+ T cells were expanded by either the multimerization reagents of the invention or Dynabeads (the various stimulating conditions were ed using y ANOVA and no significant difference (n.s.) was detected). The improved yield of the CD8+ cells using the inventive expansion methods compared to the Dynabeads might be due to the fact that the soluble multimerization reagent can access their target receptors on the cell surface better than the antibodies that are immobilized on the Dynabeads. This improved yield might become very advantageous when expanding rare population of cells from an l sample.

In addition, comparing the yield of expansion achieved with the erization agent on which both the 0.5ug uCD3 and 0.5ug (1CD28 Fab fragments were jointly immobilized (second column from the left in Fig. 203) to the yield using two multimerisation reagents which were functionalized only with the orCD3 Fab fragment alone or the (1CD28 Fab fragment alone (third column from the left in Fig. 20B), it can be seen that both experiments had the same expansion efficiency. Thus, these ments show that using one multimerization reagent on which both the first agent and the second agent are y immobilized is functionally equivalent to using for the expansion two separate multimerization reagents which are loaded with only the first agent and the second agent, respectively. e 14: Yield & phenotype of expanded CD8+ T cells — titration of separate soluble erization reagents with different ratios of aCD3- and aCD28 Fab fragment immobilized thereon In this Example the yield and the phenotype of expanded CD8+ T responder cells (Tresp) that were stimulated in vitro with aCD3/0tCD28 Fab fragments that were reversibly immobilized in ent amounts on soluble oligomeric streptavidin muteins were examined. id="p-149" id="p-149" id="p-149" id="p-149" id="p-149"

[00149] For this purpose 300.000 CD8+ responder T cells (Tresp) were stimulated with varying amounts of a mixture of preparations of the "small" oligomeric Streptactin multimerization reagent (lmg/ml) functionalized with (xCD3 Fab alone and aCD28 Fab alone (,,lx" corresponds to 1.5ug Streptactin multimerization reagent functionalized with 0.5ug 0tCD3 alone and 1.5 ug multimerized Streptactin functionalized with 0.5ug (1CD28 Fab fragment alone), or 3 ul of a preparation of the Streptactin multimerization reagent loaded with 0.5ug uCD3 and (10.5ug CD28 Fab, or 4.5 ul of a preparation of the Streptactin multimerization reagent loaded with 0.5ug uCD3, 0.5ug tagged (1CD8 and 0.5ug uCD28 Fab. Untreated Tresp cells served as ve control and Tresp stimulated with Dynabeads as positive control. Tresp cells were seeded in 48-well plates in 1ml cell culture medium supplemented with 30U/ml IL—2. Cells were incubated at 37°C without media exchange and analyzed after 5 days. Fig.21A depicts the degree of eration according to the number of cells harvested at day 5 compared to the negative controls and ized to the positive control. Fig. 21A shows that the expansion of the CD8+ T cells using the various e multimerization reagents of the invention result in higher yields of the CD8+ T cells than expansion using dynabeads (especially the cumulative total reagent amount of the 5x condition resulted in an l ion of cells especially over time/increase in total cells by ing cell division). The FACS analysis of CD8 surface expression (Fig.21B) and CD45RO surface expression (Fig. 21C) after cell culture shows that the same phenotype of CD8+ T cells were ed by either the various multimerization reagents of the invention or by the commercially available ads.

Example 15: Activation of intracellular signaling cascades after Streptamer multimers stimulation of aCD19-CAR transduced Jurkat cells In this Example the activation of intracellular signaling cascades of transduced Jurkat cells that have been modified to express a tumor-specific chimeric antigen receptor (CAR), namely here CD19 and that were stimulated using the oligomeric Strep-tactin® of Example 5 as soluble multimerization reagent was ed.

] For this purpose, 300.000 Jurkat responder cells (Jresp) were stimulated with (A) varying amounts of a mixture of preparations of Streptactin multimerization reagent (1mg/ml) functionalized with (1CD3 Fab and uCD28 Fab fragments described here (,,x1" corresponds to 3ug Streptactin multerization t fianctionalized with 0.5ug orCD3- and 0.5 ug (1CD28 Fab — this provides a "polyclonal Streptactin based multimerization reagent"), or (B) 3ul of a preparation of Streptactin multimerization t onalized with 0.5ug (X1) or lug (X2) of the extracellular domain (ECD) of CD19 (the natural ligand for the 0tCDl9- CAR — this provides a "CAR-specific Streptactin based multimerization reagent"), or 3ul of a preparation of Streptactin multimerization reagent loaded with 0.5 ug (X1) or lug (X2) aIgG izing the IgG4 spacer within the uCD19—CAR — this also provides a "CAR-specific Streptavidin mutein based multimerization t). ECD of CD19 equipped with a hexahistidine tag was obtained from Sino Biological/Life technologies (SEQ ID NO: 27) and was functionalized for binding to the streptavidin based multimerization reagent by mixing the ECD of CD19 with the adapter molecule His-STREPPER (IBA GmbH, Germany, Order number 2005) at a molecular ratio of 1:1 and incubating for 15 min at room temperature. The His-STREPPER adapter molecule contains a chelating n that binds to the hexahistidine tag and a streptavidin binding peptide, y temporarily providing the target molecule, here the ECD of CD19 with a streptavidin binding peptide that can reversibly bind to a streptavidin mutein based multimerization reagent. Jresp stimulated with Dynabeads (beads having irreversibly immobilized thereon (xCD3- and uCD28- monoclonal antibodies) or PMA and cin served as positive controls. Jresp cells were seeded in 1.5ml Eppendorf tubes in 200ul cell culture medium supplemented with 30U/ml IL-2. Cells were incubated at 37°C and put on ice and lysed after 0min to 20min of stimulation. Detection of phosphorylated ERK indicates active MAPK signaling, staining of the housekeeper B-Actin indicates loading of equal amounts of total protein per ion and time point. As can be seen from the comparison of Fig. 22A showing activation of the Jurkat cells via the "polyclonal Streptactin multimerization reagent" and Fig. 22B showing activation of the Jurkat cells via the two "CAR-specific Streptactin based multimerization ts", the Jurkat cells can be activated/expanded via the binding of the CD19 extracellular domain to the CD19 c chimeric antigen receptor. Since genetic down-stream processing of T cells is almost exclusively med on pre-selected cell populations, a generic activation via cross-linking of introduced CARS via the IgG4 spacer domain (this is conserved within various CARs with different specificities) broadens the ability for reversible cell stimulation/expansion in these in vitro cell—processing situations. id="p-152" id="p-152" id="p-152" id="p-152" id="p-152"

[00152] Thus, this experiment shows that in principle any cell population that is activated by binding of an agent (ligand) that provides a primary activation signal to the cell population can be expanded using a first agent reversibly immobilized on a multimerization reagent as described here.

Example 16: Yield and subset composition of expanded CD3+ T cells with addition of aCDS-Fab for stimulation The ment shows the ion of purified CD3+ T responder cells stimulated in vitro with dCD3/0tCD28 Fab fragments that were reversibly lized on the soluble oligomeric Strep-tactin® of Example 5 that served a soluble multimerization reagent.

In one experiment, in addition to dCD3/dCD28 Fab nts, also a aCDS Fab fragment cially available from IBA GmbH, Gottingen, Germany (catalogue number - 203) was immobilized on the soluble oligomer of the streptavidin mutein in order to test whether it is possible to preferentially stimulate a specific T cell subpopulation in vitro with the reversible aCD3/aCD28 Fab-Streptamer multimers. In more detail, 500.000 purified CD3+ responder T cells (Tresp) were stimulated with 3 ul of a ation of oligomeric Streptavidin (lmg/ml) loaded with a combination of 0.5ug ofthe dCD3 and 0.5ug ofthe dCD28 Fab. As an alternative approach, 4.5ul of the Streptactin oligomer were loaded with 0.5ug 0tCD3, 0.5ug strep-tagged 0LCD8 Fab and 0.5 pg strep-tagged (xCD28 Fab. Unstimulated Tresp cells served as negative control and Tresp stimulated with Dynabeads (beads on which dCD3 and dCD28 monoclonal antibodies are irreversible lized) served as positive control. As can be seen from Fig. 23A, the multimerization reagent that is reversibly loaded with the (XCD3 Fab fragment, the dCD28 Fab fragment and also the 0tCD8 Fab fragment provided the highest number of expanded CD3+ T cells. With 1x1 x 106 the number of expanded cells the yield was about 30 % higher than for expansion of these T cells using cially available ads. In addition and more ant, as shown in Fig. 23B with this multimerization reagent that caries the (xCD3 Fab fragment, the dCD28 Fab fragment and the (xCDS Fab fragment, the amount of CD8+ T cells were the highest, compared to both the expansion with Dynabeads or a soluble erization reagent of the invention that caries only the dCD3 Fab fragment and the (xCD28 Fab fragment as first and second agent as described herein. Thus, also this experiment shows the advantage of the present invention that in addition to a first agent that provides a primary activation signal to the desired cell population and optionally a second agent that provide a co-stimulatory signal, a further agent that is specific for the activation of the desired cell population can be immobilized on the multimerization reagent.

Thus, by so doing, the present invention provides for the ility to preferentially expand or selectively enrich any desired cell (sub)population from an sample that, for example, comprises a variety of different subpopulations.

Example 17: Parallel Antigen-specific expansion of Tcm responder cells out of a single pool id="p-154" id="p-154" id="p-154" id="p-154" id="p-154"

[00154] In this Example, the kinetics of parallel Antigen specific (Ag-specific) expansion out of a single pool of T responder cells stimulated in vitro with multiple reversible peptide:MHC/ dCH28 Fab-Streptamer multimers is examined. 500.000 CD3+CD62L+CD45RA— responder Tcm cells (Tresp) are simultaneously stimulated for multiple Ag-specificities using for each specificity, 3 ul of Streptactin multimers fianctionalized with 0.5ug of the respective peptide:MHC class I complexes that carries a avidin binding peptide and 0.5ug (1CD28 Fab that also carries a streptavidin binding peptide. As an alternative approach, 4.5 ul of Streptactin based multimerization reagent fiinctionalized with 0.5ug e:MHC class 1 complexes carrying a streptavidin binding e, 0.5ug dCD8 Fab and 0.5 ug (xCD28 Fab as described here are used for each specificity. For comparison, polyclonal stimulation is performed, using 3 ul of a preparation of Streptactin based multimerization reagent (lmg/ml) either reversibly loaded with a ation of 0.5ug (1CD3 Fab and 0.5ug (xCD28 Fab. Again as the alternative stimulation condition described above, 4.51.1.1 of a preparation of the Streptactin based multimerization reagent ibly loaded with 0.5 ug (1CD?) Fab, 0.5ug uCD8 Fab and 0.5 ug uCD28 Fab (each of them carrying a streptavidin g peptide can be used. Untreated (unstimulated) Tresp cells serve as negative control and Tresp cells stimulated polyclonal with Dynabeads (OLCD3- and — mAb coated beads) as ve control. Tresp cells are seeded in 48-well plates in lml cell culture medium supplemented with 30U/ml IL-2 and 5ng/ml IL- . Cells are incubated at 37°C with media exchange every 3 days and cell count are analyzed after 7 and 14 days.

Example 18: Preferential proliferation of CD8+ T cells among CD3+ T responder cells ated in vitro with streptavidin based erization reagents reversibly functionalized with aCD3/aCD8/aCD28 Fab fragments id="p-156" id="p-156" id="p-156" id="p-156" id="p-156"

[00156] 300.000 CD3+ der T cells ) are stimulated with 3ul of a preparation of Streptactin multimerization (lmg/ml) or a preparation of a multimerization reagent using the large Streptactin backbone (0.1mg/ml) either loaded with a combination of 0.5ug (1CD3 and 0.5ug 0LCD28 Fab, or 4.5ul of a preparation of Streptactin based multimerization reagent loaded with 0.5ug uCD3, 0.5ug (1CD8 Fab and 0.5 ug uCD28 Fab, or 3 ul of a mixture of preparations of actin based multimerization reagent with 0.5ug 0LCD3 Fab alone and 0.5ug uCD28 Fab alone (each Fab fragment again carries a streptavidin binding peptide). Untreated Tresp cells serve as negative control and Tresp stimulated with Dynabeads (uCD3- and (1CD28- mAb coated beads) as ve control. Tresp cells are seeded in duplicates in l plates in lml cell culture medium supplemented with 30U/ml IL-2.

Cells are incubated at 37°C with media exchange after 3 days and analyzed after 6 days.

Example 19: Preferential proliferation of CD8+ T cells among CD3+ T responder cells stimulated in vitro with streptavidin based multimerization reagents reversibly functionalized with aCD3 and aCD28 Fab fragments 300.000 CD3+ responder T cells (Tresp) are stimulated with varying amounts of a mixture of preparations of Streptactin based multimerization reagent l) functionalized with (xCD3 Fab nt alone and uCD28 Fab fragment alone (1.5 ug Streptactin based multimerization reagent functionalized with 0.5ug uCD3 Fab fragment alone and 1.5 ug Streptactin based erization reagent functionalized with 0.5 ug (1CD28 Fab fragment alone), or varying amounts of a mixture of preparations of Streptactin based erization reagent fianctionalized with (1CD3 Fab fragment and dCD28 Fab fragment with or without uCD8 Fab fragment (each Fab fragment again carries a streptavidin binding peptide) (3 ug Streptactin based multimerization reagent fiinctionalized with 0.5ug (1CD3- and 0.5ug 0LCD28 Fab fragment — t (1CD8 Fab fragment, or 4.5ul of a preparation of Streptactin multimerization reagent loaded with 0.5 ug (1CD3 Fab nt, 0.5ug 0LCD8 Fab fragment and 0.5ug uCD28 Fab fragment, wherein Fab fragment again carries a streptavidin binding peptide). Untreated Tresp cells serve as negative control and Tresp stimulated with ads (uCD3- and uCD28- mAb coated beads) as positive l. Tresp cells are seeded in 48-well plates in lml cell culture medium supplemented with 30U/ml IL-2. Cells are incubated at 37°C with media exchange after 3 days and analyzed afier 6 days. id="p-158" id="p-158" id="p-158" id="p-158" id="p-158"

[00158] The listing or discussion of a previously published document in this specification should not necessarily be taken as an acknowledgement that the document is part ofthe state of the art or is common l knowledge.

The invention illustratively described herein may suitably be practiced in the e of any element or elements, limitation or limitations, not specifically disclosed herein.

Thus, for example, the terms "comprising", "including," ning", etc. shallbe read expansively and without limitation. Additionally, the terms and expressions employed herein have been used as terms of description and not of tion, and there is no intention in the use of such terms and expressions of excluding any equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the invention claimed. Thus, it should be tood that although the present invention has been specifically disclosed by exemplary embodiments and optional features, modification and variation of the inventions embodied n herein disclosed may be resorted to by those d in the art, and that such modifications and variations are ered to be within the scope of this invention.

The invention has been described broadly and generically herein. Each of the narrower species and subgeneric groupings falling within the generic disclosure also form part of the invention. This includes the generic description of the invention with a proviso or negative tion removing any subject matter from the genus, regardless of whether or not the excised material is specifically recited herein.

Other embodiments are within the following claims. In addition, where features or aspects of the invention are bed in terms of Markush groups, those skilled in the art will recognize that the ion is also thereby described in terms of any individual member or up of s of the Markush group.

In a first aspect, the invention relates to a reagent kit for stimulating a population of cells, the kit comprising: (a) a first agent that (i) comprises a streptavidin-binding peptide C1 and (ii) binds to a receptor molecule on the surface of cells, thereby providing a primary tion signal to the cells; (b) a second agent that (i) comprises a streptavidin-binding peptide C2 and (ii) binds to an accessory molecule on the surface of the cells, thereby stimulating the cells; and (c) a soluble multimerization reagent comprising streptavidin or a streptavidin mutein that reversibly binds to the streptavidin-binding peptides C1 and C2.

In a second , the ion relates to a multimerization reagent capable of stimulating a population of cells, wherein the multimerization reagent is in a soluble form and is reversibly bound to a first agent comprising a streptavidin-binding peptide C1 and a second agent comprising a streptavidin-binding peptide C2; wherein the multimerization reagent comprises streptavidin or a streptavidin mutein that reversibly binds to the avidin-binding peptides C1 and C2; wherein the first agent binds to a receptor molecule on the surface of cells to provide a primary tion signal to the cells; and wherein the second agent binds to an ory molecule on the surface of the cells to stimulate an accessory signal in the cells.

Claims (53)

What is claimed is:

1. A reagent kit for stimulating a population of cells, the kit comprising: (a) a first agent that (i) comprises a streptavidin-binding peptide C1 and (ii) binds to a receptor molecule on the surface of cells, thereby providing a y tion signal to the cells; (b) a second agent that (i) comprises a streptavidin-binding peptide C2 and (ii) binds to an accessory molecule on the surface of the cells, thereby stimulating the cells; and (c) a soluble multimerization reagent comprising streptavidin or a streptavidin mutein that reversibly binds to the streptavidin-binding peptides C1 and C2.

2. The kit of claim 1, wherein the first agent comprises a MHC I:peptide complex or ates a TCR/CD3 complex-associated signal in T cells.

3. The kit of claim 1 or claim 2, wherein the first agent ses a g reagent that specifically binds CD3.

4. The kit of any of claims 1-3, wherein the accessory molecule is CD28.

5. The kit of any of claims 1-4, wherein the second agent is a binding reagent that specifically binds CD28.

6. The kit of any of claims 1-5, n: said first agent is selected from the group consisting of an anti-CD3 antibody, a divalent antibody fragment of an anti-CD3 antibody, a monovalent antibody fragment of an anti-CD3 antibody, and a proteinaceous CD3 binding molecule with antibody-like binding properties; and/or the second agent is selected from the group consisting of an anti-CD28-antibody, a nt antibody fragment of an anti-CD28 antibody, a monovalent antibody fragment of an anti-CD28-antibody, and a proteinaceous CD28 g molecule with antibody-like binding properties.

7. The kit of claim 6, n the divalent antibody fragment is an F(ab’)2 fragment, or a divalent single-chain Fv fragment.

8. The kit of claim 6, wherein the lent antibody fragment is selected from the group consisting of a Fab fragment, a Fv nt, and a single-chain Fv fragment (scFv).

9. The kit of any of claims 1-8, wherein the first agent comprises an anti-CD3 Fab and the second agent comprises an D28 Fab.

10. The kit of claim 6, wherein the proteinaceous CD3 or CD28 binding molecule with antibody-like binding properties is selected from the group of an aptamer, a mutein based on a ptide of the lipocalin family, a glubody, a protein based on the ankyrin scaffold, a protein based on the crystalline scaffold, an adnectin, and an avimer.

11. The kit of any of claims 1-10, wherein the multimerization reagent comprises an oligomer or a polymer of streptavidin or an oligomer or a r of the streptavidin mutein.

12. The kit of claim 11, wherein the oligomer or polymer is inked by a polysaccharide or via a bifunctional linker.

13. The kit of claim 11 or claim 12, wherein the oligomer or polymer comprises three or more ers of streptavidin or the streptavidin mutein.

14. The kit of any of claims 1-13, wherein the streptavidin-binding peptides C1 and C2 are different.

15. The kit of any of claims 1-13, wherein the streptavidin-binding peptides C1 and C2 are cal.

16. The kit of any of claims 1-15, wherein said streptavidin-binding peptide C1 and/or said streptavidin-binding peptide C2 is Trp-Ser-His-Pro-Gln-Phe-Glu-Lys or SAWSHPQFEK(GGGS)2GGSAWSHPQFEK (SEQ ID NO: 7).

17. The kit of any of claims 1-16, wherein the streptavidin-binding peptide C1 is fused to the C-terminus of the heavy chain of the first agent, and/or the streptavidin-binding peptide C2 is fused to the C-terminus of the heavy chain of the second agent.

18. The kit of any of claims 1-17, wherein the streptavidin mutein comprises the amino acid sequence Val44-Thr45-Ala46-Arg47 at sequence positions 44 to 47 of wild type streptavidin or the amino acid sequence Ile44-Gly45-Ala46-Arg47 at sequence positions 44 to 47 of wild type streptavidin.

19. The kit of claim 18, wherein the streptavidin mutein comprises an N-terminal amino acid residue starting at an amino acid in the region of amino acids 10 to 16 of the wildtype streptavidin amino acid sequence and a C-terminal amino acid e ending in the region of amino acids 133 to 142 of the pe streptavidin amino acid sequence.

20. The kit of any of claims 1-19, wherein the dissociation constant (Kd) for the reversible binding between said multimerization reagent and said streptavidin-binding peptide C1 and/or for the reversible binding n said multimerization reagent and said streptavidin-binding peptide C2 is in the range of 10-2 M to 10-13 M.

21. The kit of any of claims 1-20, wherein the dissociation constant (Kd) for the reversible binding between said multimerization reagent and said streptavidin-binding peptide C1 and/or the Kd for the reversible binding between said multimerization reagent and said streptavidin-binding peptide C2 is between 10-5 M and 10-10 M.

22. The kit of any of claims 1-21, wherein the reversible bond n said streptavidin-binding peptide C1 of the first agent and/or said streptavidin-binding peptide C2 of the second agent and said multimerization reagent can be disrupted in the presence of biotin or a biotin analog.

23. The kit of claim 22, wherein the biotin analog is obiotin.

24. The kit of any of claims 1-23, wherein the ible bond can be disrupted in the ce of in.

25. A multimerization reagent capable of stimulating a population of cells, wherein the multimerization reagent is in a soluble form and is reversibly bound to a first agent comprising a streptavidin-binding peptide C1 and a second agent comprising a streptavidin-binding e C2; wherein the multimerization reagent comprises streptavidin or a streptavidin mutein that reversibly binds to the streptavidin-binding peptides C1 and C2; wherein the first agent binds to a receptor molecule on the surface of cells to provide a primary activation signal to the cells; and wherein the second agent binds to an accessory molecule on the e of the cells to stimulate an accessory signal in the cells.

26. The multimerization reagent of claim 25, wherein: the first agent comprises a MHC ide complex; the first agent stimulates a 3 complex-associated signal in T cells; or the first agent comprises a binding reagent that specifically binds CD3.

27. The multimerization reagent of claim 25 or claim 26, wherein the accessory molecule is CD28 or CD137.

28. The multimerization reagent of any of claims 25-27, wherein: said first agent is selected from the group consisting of an anti-CD3 antibody, a divalent antibody fragment of an D3 antibody, a lent antibody fragment of an D3 antibody, and a proteinaceous CD3 binding molecule with antibody-like binding properties, and/or the second agent is selected from the group consisting of an anti-CD28 antibody, a divalent antibody fragment of an anti-CD28 antibody, a monovalent antibody fragment of an anti-CD28 antibody, a proteinaceous CD28 binding molecule with dy-like binding properties, an D137 antibody, a divalent antibody fragment of an anti-CD137 antibody, a monovalent antibody nt of an anti-CD137 antibody, a proteinaceous CD137 g molecule with antibody-like binding properties, 4-1BB ligand, and any mixture thereof.

29. The multimerization reagent of claim 28, wherein the divalent antibody fragment is an F(ab’)2 fragment, or a nt single-chain Fv fragment.

30. The multimerization reagent of claim 28, wherein the monovalent antibody fragment is selected from the group consisting of a Fab fragment, a Fv fragment, and a single-chain Fv fragment (scFv).

31. The erization reagent of any of claims 25-30, wherein the first agent comprises an D3 Fab and the second agent comprises an anti-CD28 Fab.

32. The multimerization reagent of claim 28, wherein the proteinaceous CD28 binding molecule or the proteinaceous CD137 g molecule with antibody-like binding properties is selected from the group of an aptamer, a mutein based on a polypeptide of the lipocalin family, a glubody, a protein based on the ankyrin scaffold, a protein based on the crystalline scaffold, an adnectin, and an .

33. The multimerization reagent of claim 25, n the first agent is a binding reagent that specifically binds CD40 or CD137.

34. The multimerization reagent of claim 25 or claim 33, wherein the first agent is ed from the group consisting of an anti-CD40 antibody, a divalent antibody fragment of an anti-CD40 antibody, a monovalent antibody fragment of an anti-CD40 antibody, a proteinaceous CD40 binding molecule with antibody-like binding properties, an anti-CD137 antibody, a divalent dy fragment of an anti-CD137 antibody, a lent antibody nt of an D137 antibody, a proteinaceous CD137 binding molecule with antibody-like binding properties, and CD40 ligand (CD154).

35. The multimerization reagent of claim 34, wherein the divalent antibody fragment is an 2 fragment, or a divalent single-chain Fv fragment.

36. The multimerization reagent of claim 34, wherein the monovalent antibody fragment is selected from the group consisting of a Fab fragment, a Fv fragment, and a single-chain Fv fragment (scFv).

37. The multimerization t of claim 34, wherein the proteinaceous CD40 binding molecule or the proteinaceous CD137 binding molecule with antibody-like g properties is selected from the group of an aptamer, a mutein based on a polypeptide of the lipocalin family, a glubody, a protein based on the ankyrin scaffold, a protein based on the crystalline scaffold, an adnectin, and an avimer.

38. The multimerization reagent of any of claims 25 and 33-37, wherein the accessory molecule is CD40 or CD137.

39. The multimerization reagent of any of claims 25 and 33-38, wherein the second agent is CD40 ligand (CD154), CD137, or a mixture thereof.

40. The multimerization reagent of any of claims 25-39, n the multimerization t comprises an oligomer or a polymer of streptavidin or an oligomer or a polymer of the streptavidin mutein.

41. The multimerization reagent of claim 40, wherein the oligomer or polymer is crosslinked by a polysaccharide or via a bifunctional linker.

42. The erization reagent of claim 40 or claim 41, wherein the oligomer or polymer comprises three or more ers of streptavidin or the streptavidin mutein.

43. The multimerization reagent of any of claims 25-42, wherein the streptavidinbinding peptides C1 and C2 are different.

44. The multimerization reagent of any of claims 25-42, wherein the streptavidinbinding peptides C1 and C2 are identical.

45. The multimerization reagent of any of claims 25-44, wherein: said streptavidin-binding peptide C1 and/or said streptavidin-binding peptide C2 is Trp-Ser-His-Pro-Gln-Phe-Glu-Lys or SAWSHPQFEK(GGGS)2GGSAWSHPQFEK (SEQ ID NO: 7).

46. The multimerization reagent of any of claims 25-45, n the avidinbinding e C1 is fused to the C-terminus of the heavy chain of the first agent, and/or the streptavidin-binding peptide C2 is fused to the C-terminus of the heavy chain of the second agent.

47. The multimerization reagent of any of claims 25-46, wherein the streptavidin mutein ses the amino acid ce Val44-Thr45-Ala46-Arg47 at sequence positions 44 to 47 of wild type streptavidin or the amino acid sequence Ile44-Gly45-Ala46-Arg47 at sequence positions 44 to 47 of wild type streptavidin.

48. The multimerization reagent of claim 47, wherein the streptavidin mutein comprises an N-terminal amino acid residue starting at an amino acid in the region of amino acids 10 to 16 of the wildtype streptavidin amino acid sequence and a inal amino acid residue ending in the region of amino acids 133 to 142 of the wildtype avidin amino acid sequence.

49. The multimerization reagent of any of claims 25-48, wherein the dissociation constant (Kd) for the reversible binding between said multimerization reagent and said streptavidin-binding peptide C1 and/or for the reversible binding n said multimerization reagent and said streptavidin-binding peptide C2 is in the range of 10-2 M to 10-13 M.

50. The multimerization reagent of any of claims 25-49, wherein the dissociation constant (Kd) for the reversible binding between said multimerization reagent and said streptavidin-binding peptide C1 and/or the Kd for the reversible binding between said erization reagent and said avidin-binding peptide C2 is between 10-5 M and 10-10

51. The multimerization reagent of any of claims 25-50, wherein the reversible bond between said streptavidin-binding peptide C1 of the first agent and/or said streptavidinbinding peptide C2 of the second agent and said erization reagent can be disrupted in the presence of biotin or a biotin analog.

52. The erization reagent of claim 51, wherein the biotin analog is desthiobiotin.

53. The multimerization reagent of any of claims 25-52, wherein the reversible bond can be disrupted in the presence of D-biotin. Juno Therapeutics GmbH By the Attorneys for the ant SPRUSON & FERGUSON Per: