NO316916B1 - Use of a bispecific antibody construct targeting CCR5 and CD3 for the preparation of a pharmaceutical composition for the treatment of chronic arthritis, autoimmune diseases, allergic reactions or for the reduction of chemokine receptor expression - Google Patents

Abstract

The invention relates to antibody and chemokine constructs against chemokine receptor expressing cells, especially against monocytes/macrophages expressing the chemokine receptor CCR5 and CCR5<+> T cells. The invention further relates to the use of antibody and chemokine constructs for destroying cells expressing the chemokine receptor for treating autoimmune diseases and allergic diseases, especially for treating chronic inflammatory diseases of the joints. The inventive antibody and chemokine constructs facilitate the specific depletion of chemokine receptor expressing cells and thus a specific immunosuppressive therapy of autoimmune diseases.

Description

The present invention relates to the use of antibody and chemokine constructs against chemokine receptor-expressing cells, especially against monocytes/macrophages, which express the chemokine receptor CCR5 and CCR5+ T cells. Furthermore, the invention relates to the use of antibody and chemokine constructs for the production of a drug for the destruction of chemokine receptor-expressing cells for the treatment of autoimmune diseases and allergic diseases, in particular for the treatment of chronic inflammatory diseases of joints. Antibody and chemokine constructs from the invention enable the direct reduction of chemokine receptor-expressing cells and thereby a targeted immunosuppressive therapy of autoimmune joint diseases.

In Germany, about 1% of the population suffers from rheumatoid arthritis. In addition, there are a number of other rheumatoid diseases that also lead to arthritis. Currently, three groups of drugs - non-steroidal antirheumatic drugs, cortisone preparations and second-line agents and TNFα-blocking agents are used in the treatment of inflammatory joint diseases. Until now, therapy has focused on local injection of cortisone preparations in combination with a systemic administration of antiphlogistics or second-line agents.

Non-steroidal anti-rheumatic drugs have a mild analgesic and anti-inflammatory effect, but they have many side effects when used frequently (e.g. gastric ulcers, nephrosis). In high doses, cortisone preparations have a strong decongestant and analgesic effect, which, however, leads to a rapid decline after the end of therapy. Moreover, cortisone preparations cannot stop the destruction process of the joint disease. A long-term therapy with cortisone usually produces serious side effects (infections, Cushing's phenomenon, osteoporosis, parchment-like skin, metabolic and hormonal disturbances). The local injection of cortisone also has the essential disadvantage that the activity of tightening white blood cells is only reduced but not destroyed, which leads to a rapid decline when the therapy ends. As mentioned above, the same happens with systemic application. Rarely is an inflammation due to the irritating effect of cortisone crystals worsened after injection of cortisone. The duration of effect of a cortisone injection varies enormously, ranging from primary ineffectiveness to a duration of effect of several weeks.

In rheumatology, the second-line agents are used to achieve a long-term suppression of the inflammation and a reduction in cortisone preparations. Due to the considerable toxicity (allergies, infections, malignant diseases, kidney insufficiency, blood pressure crises, lung diseases) it is necessary for medical specialists to be close to the patients. After starting treatment, it may be that no therapeutic effect is visible in the first three months. Currently, there are 4 or 5 such second-line agents available that are used individually first, or are combined if the therapy is not effective. For the most part, almost nothing is known about the mode of action of second-line agents. It is not yet completely clear whether the application of second-line agents can reduce the destruction of the joint. In recent years, a new group of substances has been introduced in the treatment of rheumatoid arthritis which is based on the blocking of cell signaling substances (TNFa) by means of monoclonal antibodies or soluble receptor constructions.

In addition, there are patients who do not respond to the therapies that are currently available. In other cases, conventional therapy has been stopped because of intolerable side effects.

Therefore, there is a need for a new therapeutic concept for the treatment of chronic inflammatory joint diseases, or rheumatic diseases in general, and other autoimmune diseases.

Therefore, the technical problem underlying the present invention is to provide new therapeutic agents for the treatment of inflammatory joint diseases and other autoimmune diseases as well as allergic diseases, which overcome the disadvantages of the known technique.

The features defined in the independent requirements serve to solve this problem.

Advantageous embodiments have been defined in the respective independent claims.

This technical problem has been solved by providing antibody or chemokine constructs capable of binding to a chemokine receptor on the surface of a target cell, wherein the binding of the construct to the chemokine receptor results in the destruction of the target cells. The antibody and chemokine constructs used in the invention cause target cells expressing chemokine receptors, especially leukocytes, to be selectively destroyed. The constructs include bispecific antibodies, antibody constructs, chemokine constructs, murine, chimeric or humanized antibodies, and bind both to a chemokine receptor-expressing target cell and to an antigen on the surface of effector cells, particularly a CD3 antigen, or contain a toxin. The effector cells are preferably leukocytes, especially monocytes/macrophages or T cells or dendritic cells.

In a study of more than 40 patients suffering from various joint diseases, it was found that there is a very strong concentration of monocytes/macrophages expressing the chemokine receptor CCR5 and T-lymphocytes in the inflamed joint. In the joint, more than 90% of the monocytes and T-lymphocytes express the chemokine receptor CCR5, while in the blood only 10% or 20% do this. Because of this expression pattern, the chemokine receptor CCR5, or chemokine receptors in general, is a very suitable target for cell depletion therapy. Therefore, almost all monocytes and T-lymphocytes in a joint would be affected by a CCR5 depletion, while in the bloodstream only a small number of these cells would be depleted. When it comes to chronic arthritis, monocytes and T-lymphocytes are the dominant cell types where the monocytes are mainly responsible for the joint destruction.

Surprisingly, it will now be possible to see that leukocytes expressing chemokine receptors, especially CCR5, can be destroyed by targeted methods of newly developed antibody and chemokine constructs.

While current treatment strategies essentially represent a symptomatic therapy and can influence the course of a joint disease and joint destruction only to a limited extent and second-line agents, for example, become effective only after several months and, in addition, like the other drugs that are used, has considerable toxicity when used over longer periods of time, the constructions from the invention trigger an almost complete depletion of monocytes/macrophages expressing chemokine receptors, especially CCR5+, and lymphocytes in the joint within only a few hours. These cell types are responsible for chronic inflammation and joint destruction. Due to depletion, a long-term effect can be achieved. Since the monocytes are eliminated very efficiently, the use of the antibody of the present invention enables the joint destruction to be affected in a positive way. The non-selective inhibition of the immune system by establishing second-line agents and TNFcc-blocking agents is expected to increase predisposition to infections and tumor formation. In contrast, due to the distribution of chemokine receptor-expressing cells, especially of CCR5-expressing leukocytes, the leukocytes involved in the inflammatory process can be eliminated to a high degree without influencing the immune system to any particular extent overall. All in all, the antibody makes a therapy possible that has little side effects, and which at the same time improves the course of the joint disease and prevents joint destruction.

In a preferred embodiment, the construct is a bispecific antibody with one specificity directed against a chemokine receptor, preferably against a human chemokine receptor and most preferably against the human chemokine receptor CCR5, and with the other specificity against an antigen on the surface of an effector cell, preferably against CD3 on the surface of a T cell. The invention also encompasses antibody constructs that have an identical or similar epitope specificity.

In a particularly preferred embodiment of the invention, the bispecific antibody is a single-chain antibody.

In another embodiment of the invention, the antibody construct is a bispecific antibody, one specificity which is directed against a chemokine receptor, preferably against a human chemokine receptor and most preferably against the human chemokine receptor 5 (CCR5), and the other specificity is directed against a toxin. In a preferred embodiment, also in this case, the bispecific antibody is a single-chain antibody.

In another preferred embodiment of the invention, a chemokine construct is used in the form of a chemokine toxin which is the result of the fusion of a modified or unmodified chemokine with a modified or unmodified toxin. The chemokines that bind to CCR5, such as the constructs with MIP 10, MIP la, MCP-2, MCP-3 and RANTES are particularly preferred.

In the case of the chemokine construct, the chemokine can be covalently linked to a toxin. However, the binding between the chemokine and the toxin can also take place in different ways. Via a multimerization domain, the chemokine can also be bound to an antibody that has, separated from a compatible multimerization domain, a specificity against an antigen on the surface of an effector cell, preferably against CD3 on the surface of a T cell and/or against a toxin. It is also possible to bind the chemokine via a multimerization domain to a toxin with a compatible multimerization domain. In addition, the chemokine can be covalently bound to an antibody which has a specificity against an antigen on the surface of an effector cell, preferably against CD3 on the surface of a T cell and/or against a toxin. In addition, the chemokine via a multimerization domain can be bound to a toxin via a compatible multimerization domain bound to the toxin. Binding to the multimerization domain can be performed in vitro or in vivo.

In another embodiment of the invention, the antibody construct is an antibody against a chemokine receptor, preferably against CCR5, which is covalently bound to a toxin. In this case, these are so-called immunotoxins.

Suitable toxins include, in particular, abbreviated Pseudomonas toxin, abbreviated diphtheria toxin and similar toxins.

The invention also encompasses the use of antibody constructs comprising an antibody against a chemokine receptor, preferably against CCR5, which via a multimerization domain in homodimers/heterodimers, can be bound in vitro and/or in vivo to a second antibody directed against an antigen on an effector cell, preferably against CD3 and/or against a toxin.

In addition, the invention also includes the use of antibody constructs in which an antibody against a chemokine receptor, preferably against CCR5, can be bound in vitro or in vivo via a multimerization domain to a toxin with a compatible multimerization domain.

In general, the antibody constructs, chemokine constructs and murine, chimeric or humanized antibodies are substances capable of destroying chemokine receptor-expressing cells, especially leukocytes, with this selective destruction being used for the treatment of inflammatory diseases (autoimmune diseases, allergic diseases and the like).

In connection with the invention, the term antibody or antibody constructs also includes antibody fragments that have the specificity(s) for the antibody or antibody construct, so-called active fragments.

Bispecific antibodies can be constructed using methods described below or by known methods; chemically linked antibodies or antibody fragments, the construction by means of the hybrid-hybridoma technique, the construction as bispecific single-chain antibodies, diabodies and the construction by means of linking two antibodies via multimerization domains, are just a few examples of this.

The bispecific antibodies are preferably single-chain antibodies. Different parts of these antibodies can be bound using conventional methods or constructed as adjacent protein using recombinant DNA techniques, e.g. in such a way that a nucleic acid molecule encoding a chimeric or humanized anti-substance chain is expressed to construct an adjacent protein (see, for example, Mack et al., (1995) Proe. Nati. Acad. Sei. USA, vol. 92, pp. 7021-7025).

In a particularly preferred embodiment, a single-chain antibody with the following Fv fragments is used: sc-Fv fragment of a monoclonal antibody against the chemokine receptor, preferably against CCR5 and a cs-Fv fragment from a monoclonal antibody against CD3. In this case, both the Fv fragment directed against the chemokine receptor and the Fv fragment directed against CD3, be located in the N-terminal position. The Fv fragment against CCR5 is preferred to be in the N-terminal position. The order of the VL and VH antibody domains can be variable in both constructs; the order of the Fv fragment against CCR5 is preferably VL-VH and the one of the Fv fragment against CD3 is VH-VL. The links between the variable domains as well as between the two Fv fragments consist of peptide linkers, preferably of a hydrophilic, flexible glycine- and serine-containing linker of 0-25 amino acids. An additional histidine chain of 6 x His in the C- or N-terminal position can be used to simplify the purification and detection.

Compared to conventional bispecific antibodies, bispecific single-chain antibodies have the advantage that they consist of only one protein chain, and therefore their composition is precisely defined. They have a low molecular weight of normally <60 kD, and can easily be produced on a large scale in suitable cell lines, e.g. in CHO cells, using recombinant techniques. The most essential advantage, however, is that they have no constant antibody domains, and thereby only activate T-lymphocytes to lyse when these are bound to their target cells, i.e. to the chemokine receptor-expressing cells. Therefore, single-chain antibodies are often superior to conventional bispecific antibodies, since their clinical use involves fewer or less severe side effects.

A cell of eukaryotic or prokaryotic origin can produce an antibody construct as described, in particular a bispecific antibody from the invention or an in vitro technique for protein production.

The chemokine toxins resulting from binding of a chemokine to a toxin can be constructed by chemical coupling by producing a fusion protein from a chemokine and a modified or unmodified prokaryotic or eukaryotic toxin and by binding a chemokine and a toxin via additional multimerization domains.

In a particularly preferred embodiment, a recombinantly produced fusion protein from a chemokine that binds to the human chemokine receptor CCR5 (MIP 1p, MIP la, RANTES, MCP-2, MCP-3) and a shortened version of Pseudomonas exotoxin A ( eg PE38, PE40). In this case, the chemokine is linked to the Pseudomonas toxin by means of a short peptide linker. The linker preferably consists of a flexible and hydrophilic amino acid sequence, especially of glycines and tendons, and has a length of 0 to 20 amino acids.

In addition, the technical problem from the invention is solved by providing a pharmaceutical composition comprising at least one antibody or chemokine construct from the invention, which in particular comprises at least one bispecific antibody in a quantity sufficient to destroy chemokine receptor-expressing cells, and optionally a pharmaceutically acceptable carrier.

Pharmaceutical compositions comprising the bispecific antibody are suitable for parenteral administration, i.e. subcutaneously, intramuscularly, intravenously, intra-articularly, intraperitoneally, wherein the compositions for parenteral administration usually include a solution of the antibody or a cocktail thereof, dissolved in an acceptable carrier, preferably an aqueous carrier. Suitable aqueous carriers are, for example, water, NaCl solution and glycine. In addition, the compositions may contain conventional pharmaceutically acceptable adjuvants, which are for example used to adjust the pH value, such as a buffer substance or the like.

The concentration of the bispecific antibody in the composition can vary considerably, ie from less than about 1+"<7>% w/v to 1% w/v. The concentration is preferred to be between 10"<4>% w/v and 10"<1>% w/v. For intra-articular application, the dose of the bispecific antibody should be 1 mg to

0.0001 mg, and especially about 0.02 mg, of the bispecific single chain antibody.

Therefore, for an intra-articular application in a knee joint, a suitable composition would for example comprise about 20 µg of the bispecific antibody or chemokine toxin of the invention, dissolved in about 2-5 ml of sterile NaCl solution, e.g. buffered with phosphate or Tris. An intravenous injection would also be a suitable form of application.

A further purpose of the invention is to provide new possibilities for application of the antibody as described.

This purpose is achieved by using at least one of the antibodies or one of the chemokine toxins from the invention, to deplete chemokine receptor-expressing cells. In a preferred embodiment, the antibody or chemokine toxin of the invention is used for the preparation of a pharmaceutical composition to treat chronic arthritis and other autoimmune diseases or allergic diseases.

The selective chemokine receptor depletion, especially the CCR5 depletion, has two significant advantages compared to previous immunosuppressive therapies (e.g. cortisone, methotrexate, cytokine blockade): First, previous therapies do not target depletion of the infiltrating leukocytes, but only lead to a suppression of the activity. This leads to a rapid return after termination of therapy, and requires permanent immunosuppression. In contrast to this, when it comes to depletion of the responsible leukocytes in the joint, there is hope that a long-lasting decline can already be achieved already after one or a few treatments. The other advantage of a chemokine receptor depletion is that, due to the distribution of cells expressing chemokine receptors, especially CCR5, only cells involved in the inflammatory process are depleted. However, the other cells remain largely intact.

The mode of action of the bispecific antibody, one specificity directed to a chemokine receptor, and the other specificity to an antigen on the surface of T cells performing cells, is illustrated in Figure 1 (top) and Figure 2, using a preferred embodiment of the invention. As shown in Figure 1 (top), a bispecific antibody binds with its two arms to two different antigens. In a preferred embodiment, these are the chemokine receptor CCR5 and the surface molecule CD3 on T lymphocytes. As shown in Figure 2, the bispecific antibody leads to a cross-linking of T lymphocytes and CCR5-expressing cells. Because of the cross-linking, the T-lymphocytes are activated to lyse, and the CCR5+ cells bound thereto are destroyed. As a consequence, a lysis of CCR5+ cells only takes place in the presence of T lymphocytes. These are present in large quantities with all forms of chronic arthritis. In this way, it is particularly possible to purposefully eliminate the cells responsible for the inflammation by injecting the bispecific antibody into the inflamed joint.

Further embodiments of the invention and their mode of operation are illustrated in the attached figures 1 to 9.

Due to the possibility of deliberately depleting chemokine receptor-expressing cells, the concept is not only suitable for chronic arthritis, but also for rheumatic diseases and other autoimmune diseases that were found to have a similarly strong concentration of cells expressing chemokine receptors, especially CCR5.

While various possibilities for using bispecific antibodies in the treatment of tumors have already been reported (eg, Kroesen, BJ. et al. (1993) Cancer Immunol. Immunother. 37:400-7; Nitta. T. et al. (1990) Lancet 335:368-71; Bolhuis, R. L. et al. (1992) Int. J. Cancer Suppl., 7:78-81; Canevari, S. et al. (1995) J. Nat. Cancer Inst. . 87:1463-9; De gast, G. et al. (1995) J. Hematother. 4:433-437; Kroesen, B.J. et al. (1994) Br. J. Cancer, 70:652-61; Tibben , J.G. et al (1993) J. Nat. Cancer Inst. 85:1003.4), the application of bispecific antibodies for immunosuppression has not been described heretofore.

Description of the figures:

Figure 1 shows antibody and chemokine constructs of the invention that cause cross-linking of target cells, in this case CCR5-expressing cells and effector cells, in

in this case T cells with CD3 on the surface, top: Bispecific antibody with specificities both against CCR5 and CD3, middle: Chemokine construct consisting of a chemokine and an antibody against CD3, below: Chemokine construct in which a chemokine with a multimerization domain can bind to an antibody directed against CD3 via a compatible multimerization domain.

As shown schematically in Figure 2, the cross-linking leads to the activation of T-lymphocytes to lysis and to the destruction of CCR5-positive cells cross-linked thereto.

Figure 3 shows antibody and chemokine constructs from the invention that lead to a binding between target cells, in this case CCR5-expressing cells and a toxin, top: Bispecific antibody that has specificities against both CCR5 and a toxin, below: Chemokine construct consisting of a chemokine and an antibody against a toxin.

The cross-linking of a target cell and a toxin as illustrated in Figure 4 leads to cell death of the CCR5-positive target cell.

Figure 5 shows, in the same way as Figure 3, antibody and chemokine constructs that lead to a binding between a target cell and a toxin, in which, however, the toxin is not bound via the specificity of an antibody directed against the toxin, but is either covalently bound to an antibody directed against the chemokine receptor , preferably against CCR5 (Figure 5, top), or to a chemokine (Figure 5, middle), or can, via a multimerization domain, be bound to an antibody with a compatible multimerization domain directed against a chemokine receptor (Figure 5, bottom).

As has been shown in Figure 6, the cross-linking of a target cell and a toxin also leads to cell death of the target cell. Figure 7 shows the result of a FACS analysis (performed as described in Mack et al. (1998) J. Exp. Med. 187, pp. 1215-1224), which explains the depletion of CCR5-positive T cells and monocytes from the the inflamed synovial joint fluid of a patient with chronic polyarthritis or from cultured peripheral blood leukocytes (PBMC). Figure 8 shows the cytotoxicity of the chemokine toxin Ra-PE38, or more precisely, the destruction of CCR5-expressing CHO cells by the chemokine toxin Ra-PE38 (10 ng/ml) after a 24 hour incubation (right, below). The CHO cells expressing the chemokine receptor CXCR4 instead of CCR5 are not destroyed by Ra-PE38 (top) since RANTES does not bind to CXCR4. Incubation with medium does not kill CHO cells. Ra-PE38 - a fusion protein of RANTES and a shortened Pseudomonas exotoxin with a molecular weight of 38 kD'.

Figure 8 explains the approach described in Figure 5, middle.

Figure 9 shows a 48 hour incubation of synovial fluid with CD3-CCR5 bispecific antibodies. Therefore, figure 9 should be seen in connection with figure 7, at the top. There is a concentration-dependent depletion of the T-lymphocytes and monocytes. At an antibody concentration of 125 ng/ml, monocytes and T lymphocytes were reduced by 96% and 97.5%, respectively.

The present invention comprises the use of a bispecific antibody construct capable of binding to a human chemokine receptor CCR5 as a first antigen and a CD3 antigen on the surface of an effector cell as a second antigen, and active fragments of said bispecific antibody constructs for the production of a pharmaceutical composition for the treatment of chronic arthritis, autoimmune diseases or allergic diseases.

The present invention also encompasses the use of at least one bispecific antibody construct as defined in any one of claims 1 to 8 for the preparation of a pharmaceutical composition for the "depletion" of chemokine receptor expressing cells.

EXAMPLES

Example 1: Concentration of a bispecific antibody

For the construction of bispecific antibodies, for example, the single-chain technique can be used (Mack et al. (1995) Proe. Nati. Acad. Sei. USA, 92:7021-7025; Mack et al. (1997) J. Immunol. 158: 3965-3970). In this case, as shown schematically in Figures 1 (top) and 3 (top), the variable domains of the light (VL) and heavy (VH) immunoglobulin chains of two different antibodies are fused together in a particular order, optionally a histidine chain of 6 x His is additionally attached. The fusion is effected on the basis of a DNA, so that a protein chain with four different variable domains is formed after expression (cf. figures 1 (top) and 3 (top)). The attached histidine chain enables a simple and effective purification via immobilized Ni ions in one step. Figure 1 (top) shows a preferred embodiment of the bispecific antibody binding to the CD3 antigen on the surface of the effector cell and the human CCR5 on the surface of leukocytes as target cells.

By means of RT-PCR, the variable antibody domains from the hybridoma cells that form the desired antibody are amplified. The PCR fragments thus acquired are cloned into a vector and sequenced. Then, a single-chain antibody with a specificity is generated by fusion PCR by inserting a linker of (Gly4Seri)3 between the two antibody variable domains. In a further fusion PCR, the antibody fragment against CCR5 is fused to the already published antibody fragment against CD3, with a linker consisting of Gly4Seri inserted (cf. Mack et al. supra). The following order of the domains has been chosen: VL(1)-VH(1)-VH(2)-VL(2), where (1) is the specificity against CCR5 and (2) the specificity against CD3.

Example 2: Expression and purification of the bispecific antibody from Example 1

To express the bispecific antibody, the corresponding DNA sequence is subcloned into a eukaryotic expression vector (eg, PEF-DHFR, Mack et al. (1995) PNAS, supra) and transfected into DHFR-deficient CHO cells by electropo -rering. The bispecific antibody is purified from the supernatant of stably transfected CHO cells by affinity chromatography on Ni-NTA, with elution by lowering the pH. The pH is then adjusted, and the protein is adjusted to a suitable concentration.

Example 3: In v/ frost tests for blood leukocytes and leukocytes in inflamed joints

For the in v/fro tests, joint effusion fluid that includes the cells is incubated with the bispecific antibodies for one or more days. After 24 hours, CCR5-positive lymphocytes and monocytes have already almost disappeared. When the medium is checked after longer incubation, the monocytes have differentiated into macrophages which are visible at the bottom of the culture flask. After a suitable incubation with the bispecific antibody, no macrophages are visible.

A corresponding result can be obtained when cultured PBMCs are incubated with the bispecific antibody. In this case, there is a complete depletion of CCR5-positive monocytes and an almost complete depletion of CCR5-positive T lymphocytes. The depletion of CCR5-positive T cells and monocytes is shown in Figure 7.

The results showed, in accordance with Example 1, that the construct of the invention is capable of completely destroying CCRS-positive monocytes. This is used both for monocytes from the joint aspirate and the blood monocytes that express CCR5 when this is differentiated into macrophages. Depletion of monocytes/macrophages takes place within a few hours (< 25 hours). In particular, the depletion of monocytes/macrophages in the joint is of great benefit in therapy, since it is these cells that are mainly responsible for the joint destruction. Moreover, when it comes to the activation of T-lymphocytes, an interaction with macrophages is also required, so that the function of T-lymphocytes is at the same time suppressed.

In addition to the depletion of monocytes/macrophages, a considerable reduction in the number of CCR5-positive T-lymphocytes could be observed.

Claims (9)

1. Use of a bispecific antibody construct capable of binding to a human chemokine receptor CCR5 as a first antigen and a CD3 antigen on the surface of an effector cell as a second antigen for the preparation of a pharmaceutical composition for the treatment of chronic arthritis, autoimmune diseases or allergic diseases. 2. The use according to claim 1, where said bispecific antibody construct is a single-chain antibody or a diabody or a construct comprising two antibodies bound via a multimerization domain in homodimers/heterodimers. 3. The use according to claim 2, where said bispecific single-chain antibody comprises an scFv fragment of a monoclonal antibody directed against human CCR5 as well as scFv fragment from a monoclonal antibody directed against CD3. 4. The use according to claim 3, where said scFv fragment against CCR5 is located in the N-terminal part. 5. The use according to any one of claims 2 to 4, where the bispecific single antibody comprises the following sequence of antibody domains: where (1) is specific against CCR5 and (2) is specific against CD3. 6. The use according to any one of claims 3 to 5, where the links between the variable domain as well as between the two Fv fragments consist of peptide linkers. 7. The use according to claim 6, where the bispecific antibody constructs comprise linkers consisting of hydrophilic, flexible glycine- and serine-containing linkers of 0-20 amino acids. 8. The use according to any one of claims 1 to 7, wherein the effector cell is a leukocyte, in particular a monocyte/macrophage or a T cell, or a dendritic cell. 9. The use of at least one bispecific antibody construct capable of binding to a human chemokine receptor CCR5 as a first antigen and a CD3 antigen on the surface of an effector cell as a second antigen for the preparation of a pharmaceutical composition for the reduction of chemokine receptor expressing cells.