CA2704119A1 - Humanized anti-venezuelan equine encephalitis virus recombinant antibodies - Google Patents

Abstract

A CDR grafted humanized recombinant antibody against infection from Venezuelan equine encephalitis virus (VEEV) comprises a human Ig framework having CDRs from murine mAb 1A4A1 VH and VL. DNA sequences, expression vectors incorporating such sequences and transformed host cells are also provided. Also provided are pharmaceutical compositions and methods of prophylaxis and treatment against VEEV infection using the humanized recombinant antibodies of the invention.

Description

Agent Ref: 67853/00022 4 [0001] The present application claims priority from Canadian patent application number 2,607,771 filed on November 1, 2007. The present application is a Continuation in Part of U.S.
6 patent application number 11/933,948, filed on November 1, 2007. The entire contents of the above 7 mentioned prior applications are incorporated herein by reference.

9 [0002] The present invention relates to a humanized antibodies (Abs) and, more specifically, to humanized recombinant antibodies (rAbs) against infection by the Venezuelan equine encephalitis 11 virus (VEEV). The invention provides methods of prophylaxis and treatment against VEEV using 12 such antibodies.

14 [0003] Venezuelan equine encephalitis virus (VEEV), a member of the alphavirus genus of the family Togaviridae, is an important mosquito-borne pathogen in humans and equides [1]. VEEV
16 infections mainly target the central nervous system and lymphoid tissues causing severe 17 encephalitis in equines and a spectrum of human diseases ranging from unapparent or sub-clinical 18 infection to acute encephalitis. Neurological disease appears in 4-14% of cases. The incidence of 19 human infection during equine epizootics could be up to 30%. Mortality associated with the encephalitis in children is as high as 35%. Recent outbreaks in Venezuela and Colombia in 1995 21 resulted in around 100,000 human cases with more than 300 fatal encephalitis cases [2].
22 Furthermore, VEEV is highly infectious by aerosol inhalation in humans and other animals.
23 However, there are no antiviral drugs available that are effective against VEEV although currently 24 there are two forms of IND (investigational new drug) VEEV vaccines available for human and veterinary use: TC-83, a live-attenuated Trinidad donkey strain and C-84, a formal in-inactivated TC-26 83 [3,4]. However, for various reasons, these vaccines are far from satisfactory. For example, 27 approximately 20% of recipients that receive the TC-83 vaccine fail to develop neutralizing Abs, 28 while another 20% exhibit reactogenicity. In addition, the TC-83 vaccine could revert to wild-type 29 form. The vaccine C-84 is well tolerated, but requires multiple immunizations, periodic boosts, and fails to provide protection against aerosol challenge in some rodent models.

21989275.1 1 Agent Ref: 67853/00022 1 [0004] Like the other alphaviruses, VEEV is an enveloped virus, consisting of three structural 2 proteins: a capsid encapsidating the viral RNA genome, and two envelope glycoproteins, El and 3 E2. El and E2 form heterodimers, which project from the virus envelope as trimer spikes. Epitopes 4 on the spikes are the targets of neutralizing Abs. Studies have shown that the viral neutralizing epitopes are mainly located on the E2 protein, and that the E2C epitope appears to be the hub of the 6 neutralization epitopes [5,6]. The murine monoclonal Ab (mAb) 1A1A4 [14] is specific for E2C. This 7 mAb has been shown to be efficient in protecting animals from a lethal peripheral challenge with 8 virulent VEEV [7].

9 [0005] Murine mAbs, however, have serious disadvantages as therapeutic agents in humans [8]. For example, one of the problems associated with using murine mAbs in humans is that they 11 may induce an anti-mouse Ab response. Further, repeat administration of murine mAbs may result 12 in rapid clearance of the murine mAbs and anaphylaxis, which can sometimes be fatal. To 13 overcome this hurdle, the humanization of murine mAbs has been proposed, by which process 14 murine Ab frameworks are replaced by human Ab ones in order to reduce immunogenicity of Abs in humans [9,10].

16 [0006] An effective means of immunization againt VEEV is needed. In particular, a means of 17 prophylaxis against VEEV and/or a therapy for VEEV infection is desired.

19 [0007] In one aspect, the present invention provides prophylaxis and post-exposure therapy against VEEV infection.

21 [0008] In one aspect, the invention provides a humanized rAb comprising a human 22 immunoglobulin (Ig) framework and having grafted thereon complementarity determining regions 23 (CDRs) from the murine mAb 1A4A1. In a preferred embodiment, the human Ig framework is 24 obtained from IgG1.

[0009] In another aspect, the invention provides a humanized rAb having specificity to the E2 26 envelope protein of VEEV. More specifically, the rAb has specificity to the E2c epitope of the E2 27 protein.

28 [0010] In another aspect, the invention provides a humanized rAb wherein the complementarity 29 determining regions CDR1, CDR2 and CDR3 of the heavy chain variable region (VH) have the following amino acid sequences:
31 CDR1: SEQ ID NO: 1 21989275.1 2 Agent Ref: 67853/00022 1 CDR2: SEQ ID NO: 2 2 CDR3: SEQ ID NO: 3.

3 [0011] In another aspect, the invention provides a humanized rAb wherein the complementarity 4 determining regions CDR1, CDR2 and CDR3 of the light chain variable region (VL) have the following amino acid sequences:
6 CDR1: SEQ ID NO: 4 7 CDR2: SEQ ID NO: 5 8 CDR3: SEQ ID NO: 6.

9 [0012] In a further aspect, the invention provides a humanized rAb having a VH comprising the amino acid sequence of SEQ ID NO: 7.

11 [0013] In a further aspect, the invention provides a humanized rAb having a VL comprising the 12 amino acid sequence of SEQ ID NO: 8.

13 [0014] In another aspect, the invention provides a DNA sequence which encodes a polypeptide 14 corresponding to a CDR grafted VH having the amino acid sequence according to SEQ ID NO: 7.
[0015] In another aspect, the invention provides a DNA sequence which encodes a polypeptide 16 corresponding to a CDR grafted VL having the amino acid sequence according to SEQ ID NO: 8.

17 [0016] In a further aspect, the invention provides a DNA construct having a nucleic acid 18 sequence according to SEQ ID NO:11 or SEQ ID NO:13.

19 [0017] In another aspect, the invention provides an expressed protein comprising a humanized rAb having an amino acid sequence according to SEQ ID NO: 12 or SEQ ID NO: 14.

21 [0018] The invention provides vectors containing such DNA sequences and host cells 22 transformed thereby.

23 [0019] In other aspects, the invention provides methods and uses for treatment and/or 24 prophylaxis against VEEV infection comprising the antibodies described herein. The invention also provides pharmaceutical preparations for such treatment or prophylaxis.

27 [0020] These and other features of the invention will become more apparent in the following 28 detailed description in which reference is made to the appended drawings wherein:

29 [0021] Figure 1 is a representation of the external structure of the VEEV.
21989275.1 3 Agent Ref: 67853/00022 1 [0022] Figures 2a to 2d schematically illustrate murine, human, chimeric and humanized Abs, 2 respectively.

3 [0023] Figures 3a to 3c schematically illustrate the humanization of the murine Ab variable 4 region.

[0024] Figure 4 schematically illustrates the cloning of the murine Ab VH and VL.

6 [0025] Figure 5 schematically illustrates the humanization of the Ab VH and shows its amino 7 acid sequence.

8 [0026] Figure 6 schematically illustrates the humanization of the Ab VL and shows its amino 9 acid sequence.

[0027] Figure 7 schematically illustrates the design of a full Hu1A4A1IgG1 rAb gene in a single 11 open reading frame with two versions, Hu1A4A1IgG1-furin and Hu1A4A1lgG1-2A.

12 [0028] Figure 8 schematically illustrates the cloning of the Hu1A4A1IgG1-furin and 13 Hu1A4A1IgG1-2A genes into an adenoviral vector respectively.

14 [0029] Figure 9 schematically illustrates expression and purification of the Hu1A4A1IgG1-furin and Hu1A4A1lgG1-2A rAbs.

16 [0030] Figures 10 and 11 illustrate the results from the SDS-PAGE
separation of the produced 17 Hu1A4A1IgG1-furin rAb.

18 [0031] Figure 12 illustrates the results from the sodium dodecyl sulfate-polyacrylamide gel 19 electrophoresis (SIDS-PAGE) separation of the produced Hu 1 A4A1 IgG 1 -2A
rAb.

[0032] Figure 13 illustrates the results of the enzyme-linked immunosorbent assays (ELISA) for 21 the reactivity of the Hu1A4A1IgG1-furin and Hu1A4A1IgG1-2A rAbs.

22 [0033] Figure 14 schematically illustrates Hu 1 A4A1 IgG I -2A was cleaved between the heavy 23 and light chains as expected, whereas Hu1A4A1IgG1-furin was not cleaved.

24 [0034] Figure 15 schematically illustrates the neutralization assay used in assessing the neutralizing activity of the Hu1A4A1IgG1-furin and Hu1A4A1IgG1-2A rAbs against VEEV.
21989275.1 4 Agent Ref: 67853/00022 2 [0035] The terms "monoclonal antibody" or "monoclonal antibody composition"
as used herein 3 refer to a preparation of antibody molecules of single molecular composition. A monoclonal antibody 4 composition displays a single binding specificity and affinity for a particular epitope.

[0036] The term "recombinant antibody", as used herein, refers to antibodies that are prepared, 6 expressed, created or isolated by recombinant means, such as (a) antibodies isolated from an 7 animal (e.g., a mouse) that is transgenic or transchromosomal for immunoglobulin genes or a 8 hybridoma prepared therefrom, (b) antibodies isolated from a host cell transformed to express the 9 antibody, e.g., from a transfectoma, (c) antibodies isolated from a recombinant, combinatorial antibody library, and (d) antibodies prepared, expressed, created or isolated by any other means 11 that involve splicing of immunoglobulin gene sequences to other DNA
sequences.

12 [0037] As used herein the terms "expression vector" or "cloning vector"
include vectors which 13 are designed to provide transcription of the nucleic acid sequence. The transcribed nucleic acid may 14 be translated into a polypeptide or protein product. As used herein, the term "vector" refers to a nucleic acid molecule capable of transporting another nucleic acid to which it has been linked. One 16 type of vector is a "plasmid", which refers to a circular double stranded DNA loop into which 17 additional DNA segments can be ligated. Another type of vector is a viral vector, wherein additional 18 DNA segments can be ligated into the viral genome. Certain vectors are capable of autonomous 19 replication in a host cell into which they are introduced (e.g., bacterial vectors having a bacterial origin of replication). Other vectors are integrated into the genome of a host cell upon introduction 21 into the host cell, and thereby are replicated along with the host genome.
Moreover, certain vectors 22 are capable of directing the expression of genes to which they are operatively-linked. Such vectors 23 are referred to herein as "expression vectors" or "cloning vectors". In general, expression vectors of 24 utility in recombinant DNA techniques are often in the form of plasmids. In the present specification, "plasmid" and "vector" can be used interchangeably as the plasmid is the most commonly used form 26 of vector. However, the invention is intended to include such other forms of expression vectors, 27 such as viral vectors or plant transformation vectors, binary or otherwise, which serve equivalent 28 functions.

29 [0038] The recombinant expression vectors of the invention comprise a nucleic acid of the invention in a form suitable for expression of the nucleic acid in a host cell, which means that the 31 recombinant expression vectors include one or more regulatory sequences, selected on the basis of 32 the host cells to be used for expression, that is operatively-linked to the nucleic acid sequence to be 33 expressed. Within a recombinant expression vector, "operatively-linked" or "operably-linked" is 21989275.1 5 Agent Ref: 67853/00022 1 intended to mean that the nucleotide sequence of interest is linked to the regulatory sequence(s) in a 2 manner that allows for expression of the nucleotide sequence (e.g., in an in vitro 3 transcription/translation system or in a host cell when the vector is introduced into the host cell).

4 [0039] The term "regulatory sequence" is intended to include promoters, enhancers and other expression control elements (e.g., polyadenylation signals). Such regulatory sequences are well 6 known in the art such as, for example, in Goeddel, Gene Expression Technology: Methods in 7 Enzymology 185, Academic Press, San Diego, Calif. (1990). Regulatory sequences include those 8 that direct constitutive expression of a nucleotide sequence in many types of host cells and those 9 that direct expression of the nucleotide sequence only in certain host cells (e.g., tissue-specific regulatory sequences) or inducible promoters (e.g., induced in response to abiotic factors such as 11 environmental conditions, heat, drought, nutrient status or physiological status of the cell or biotic 12 such as pathogen responsive). Examples of suitable promoters include for example constitutive 13 promoters, ABA inducible promoters, tissue specific promoters and abiotic or biotic inducible 14 promoters. It will be appreciated by those skilled in the art that the design of the expression vector can depend on such factors as the choice of the host cell to be transformed, the level of expression 16 of protein desired as well as timing and location of expression, etc. The expression vectors of the 17 invention can be introduced into host cells to thereby produce proteins or peptides, including fusion 18 proteins or peptides, encoded by nucleic acids as described herein.

19 [0040] The terms "host cell" and "recombinant host cell" are used interchangeably herein. It is understood that such terms refer not only to the particular subject cell but also to the progeny or 21 potential progeny of such a cell. Because certain modifications may occur in succeeding 22 generations due to either mutation or environmental influences, such progeny may not, in fact, be 23 identical to the parent cell, but are still included within the scope of the term as used herein.

24 [0041] Vector DNA can be introduced into prokaryotic or eukaryotic cells via conventional transformation or transfection techniques. As used herein, the terms "transformation" and 26 "transfection" are intended to refer to a variety of art-recognized techniques for introducing foreign 27 nucleic acid (e.g., DNA) into a host cell.

28 [0042] A host cell of the invention, such as a prokaryotic or eukaryotic host cell in culture, can 29 be used to produce (i.e., express) a polypeptide of the invention encoded in an open reading frame of a polynucleotide of the invention. Accordingly, the invention further provides methods for 31 producing a polypeptide using the host cells of the invention. In one embodiment, the method 32 comprises culturing the host cell of invention (into which a recombinant expression vector encoding 33 a polypeptide of the invention has been introduced) in a suitable medium such that the polypeptide is 21989275.1 6 Agent Ref: 67853/00022 1 produced. In another embodiment, the method further comprises isolating the polypeptide from the 2 medium or the host cell.

3 [0043] Figure 1 illustrates the external structure of the VEEV. As shown, the virus 10 includes a 4 nucleocapsid 12 enveloping the viral RNA genome. The envelope comprises glycoproteins El and E2, arranged in the form of heterodimers 14. Protein E2, which is responsible for viral attachment to 6 the host cell, contains neutralizing epitopes.

7 [0044] As has been described in the prior art, the murine mAb 1A4A1 has been found to be 8 specific to the VEEV E2 envelope protein and, further, has been found to have a strong neutralizing 9 function against VEEV. The murine mAb, however, causes a sometimes fatal allergenic reaction in humans, resulting in the formation of human anti-mouse Abs (HAMA). It is for this reason that the 11 present inventors have sought to humanize the 1A4A1 mAb so as to provide an effective agent to 12 counter VEEV infection in humans. In the course of this research, humanized recombinant anti-13 VEEV monoclonal antibodies have recently been designed and developed [18].
Such recombinant 14 antibodies are described further herein and are the subject of Canadian patent application number 2,607,771 and U.S. patent application number 11/933,948, both filed on November 1, 2007. The 16 present invention provides methods and uses involving such antibodies for the prevention 17 (prophylaxis) and treatment against VEEV infection in mammals.

18 [0045] In vivo efficacy studies in mice have demonstrated that treatment with murine mAb 19 1A4A1 leads to protection of animals from a lethal peripheral challenge with virulent VEEV. Thus, the present invention builds upon these findings by providing a humanized mAb 1A4A1 to reduce the 21 foreignness of murine mAb in humans. For doing this, the majority of the non-human protein 22 sequence (in one embodiment, more than 90%) of mAb 1A4A1 is replaced with a human Ab 23 sequence and the resultant whole humanized mAb gene is then synthesized and cloned to an 24 expression vector such as an adenoviral vector. The recombinant adenoviral vector can be delivered as a therapeutic agent for prophylaxis or treatment of VEEV
infection in humans. One 26 advantage of this method is that the vector can express the humanized Ab in the human body for a 27 long period of time. The humanized Ab can also be produced in cell culture and delivered directly as 28 a therapeutic.

29 [0046] The humanization of the present anti-VEEV mAb 1A4A1 has not been done previously and particularly not for the prophylaxis or treatment of VEEV infection. The present invention 31 provides in one embodiment a humanized Ab, referred to herein as Hu1A4A1IgG1, that retains the 32 VEEV-binding specificity and neutralizing activity of murine 1A4A1 while not eliciting a HAMA
33 response. As described further below, the humanized Ab comprises an Ig framework of human 21989275.1 7 Agent Ref: 67853/00022 1 IgG1 and CDRs obtained from murine mAb 1A4A1. The rAb of the present invention is specific to 2 an epitope of the E2 envelope glycoprotein of VEEV and, more specifically, to the E2c epitope 3 thereon.

4 [0047] The construction of the humanized Ab of the invention is schematically illustrated in Figures 2a to 2d. Figure 2a illustrates schematically the structure of a murine Ab 16 containing 6 murine CDRs 18 on the respective variable regions. Figure 2b shows a human Ab 20 containing 7 human CDRs 22. As shown in Figure 2c, a chimeric Ab 26 would comprise the murine variable 8 regions 24, containing the murine CDRs 18, joined to the constant regions of the human Ab. On the 9 other hand, Figure 2d illustrates a humanized Ab 28 according to an embodiment of the invention, wherein only the murine CDRs 18 are grafted to the variable regions of the human Ab 20.

11 [0048] The substitution of the murine CDRs into the human Ig framework is illustrated also in 12 Figures 3a to 3c. As shown, the humanized Ab variable region comprises the grafted CDRs, 18, 13 from the murine Ab.

14 [0049] The protein sequences of the rAbs of the invention include linker sequences. The expressed rAbs of the invention have amino acid sequences as shown in SEQ ID
NO:12 and SEQ
16 ID NO:14. The nucleic acid constructs used in transforming cells to express the above rAbs are 17 shown in SEQ ID NO:11 and SEQ ID NO:13.

18 [0050] As illustrated further below, the humanized recombinant antibodies of the present 19 invention have been found to be effective as both a prophylaxis and a treatment against VEEV
infection.

21 [0051] Examples 22 [0052] The following examples are provided to illustrate embodiments of the present invention.
23 The examples are not intended to limit the scope of the invention in any way.

24 [0053] Example 1: Construction of Hu1A4A1IgG1 and in vitro studies [0054] In the study described below, murine mAb 1A4A1 CDRs of VH, VL were grafted onto the 26 frameworks of germline variable and joining (V, J) gene segments of human Ig heavy and light 27 chains, respectively, which were chosen based on the CDR similarities between human Igs and 28 murine mAb 1A4A1. Furthermore, the humanized VH and VL were, respectively, grafted onto 29 human gamma 1 heavy chain constant regions (CHs) and kappa 1 light chain constant region (CL) to assemble the whole humanized Ab gene. The resultant whole humanized mAb gene was 31 synthesized and cloned to an adenoviral vector. After the humanized Ab was expressed in HEK 293 21989275.1 8 Agent Ref: 67853/00022 1 cells and purified with protein L column, the Ab was demonstrated to retain antigen-binding 2 specificity and neutralizing activity.
3 [0055] Materials and Methods 4 [0056] Humanization of murine mAb 1A4A1 [0057] Murine mAb 1A4A1 was provided by Dr. J.T. Roehrig (Division of Vector-borne Infectious 6 Diseases, Centers for Disease Control and Prevention, Fort Colins, CO, USA).
The VH and VL of 7 mAb 1A4A1 were cloned in a single chain variable fragment (ScFv) format, mA116 previously [7], 8 which showed to retain the same binding specificity as mAb 1A4A1 [11]. The humanization of VH
9 and VL of murine mAb 1A4A1 was done by Absalus Inc. (Mountain View, CA, USA). Briefly, in order to select human VH and VL frameworks 1-3, the VH and VL amino acid sequences of murine 1A4A1 11 were separately subjected to IgBlast and IMGT searches against the entire human Ig germline V
12 gene segments and then human heavy and light chain germline V gene segments were selected 13 based on their highest CDR 1 and 2 similarities with those of murine 1A4A1 VH and VL without 14 consideration of framework similarity. Both human VH and VL framework 4 were selected, respectively, from human heavy and light chain J gene segments based on the highest similarities 16 between human J gene segments and murine 1A4A1 VH and VL CDR3. Finally, CDRs of murine 17 1A4A1 VH and VL were, respectively, grafted onto the frameworks of selected germline V and J
18 gene segments of human Ab heavy and light chains, resulting in humanized 1A4A1 (Hu1A4A1).
19 Furthermore, the Hu1A4A1 VH and VL were, respectively, grafted onto human gamma 1 heavy chain CHs and kappa 1 light chain CL to assemble the whole humanized Ab gene, resulting in 21 humanized 1A4A1IgG1 (Hu1A4A1IgG1). This process is illustrated in Figures 3 to 6.

22 [0058] Construction, expression and purification of Hu1A4A1 IqG1 (Hu1A4A1IgG1-furin and 23 Hu1A4A1IgG1-2A) 24 [0059] The Hu1A4A1IgG1 DNA sequence (-2 kb) is schematically illustrated in Figure 7. The nucleic acid sequence of the Hu1A4A1IgG1-furin rAb is provided in SEQ ID NO:11 and the nucleic 26 acid sequence of the Hu1A4A1IgG1-2A rAb is provided in SEQ ID NO:13.

27 [0060] The Hu1A4A1IgG1 DNA sequences were synthesized as follows. As shown in Figure 7, 28 a light chain leader sequence was provided upstream from the light chain, followed by a furin or 2A
29 linker (discussed further below) before the heavy chain. The whole DNA
sequence flanked by Kpn I
and Hind III was synthesized by GenScript Corporation (Scotch Plaines, NJ, USA) and cloned into 31 pUC57 vector, resulting in pUC57-Hu1A4A1IgG1-furin or pUC57-Hu1A4A1IgG1-2A.

21989275.1 9 Agent Ref: 67853/00022 1 [0061] Recombinant adenovirus vectors expressing either Hu1A4A1IgG1-furin or 2 Hu1A4A1IgG1-2A were constructed using AdEasyTM system (Qbiogene, Carlsbad, CA, USA) 3 according to the manufacturer's protocol. Briefly, the Kpn I-Hind I I I
fragment of Hu 1 A4A1 IgG 1 -furin 4 or Hu1A4A1IgG1-2A was ligated to a Kpn I-Hind III-digested pShuttle-CMV
vector. The resulting pShuttle construct was co-transformed with the pAdEasy-1 vector into Escherichia coli BJ5183 cells 6 to produce recombinant adenoviral genomic constructs for Hu1A4A1IgG1-furin or Hu1A4A1IgG1-2A
7 proteins. The recombinant adenoviral constructs, pAd-Hu1A4A1IgG1-furin and pAd-Hu1A4A1IgG1-8 2A were linearized with Pac I and transfected into HEK 293 cells (American Type Culture Collection, 9 Manassas, VA, USA) cultured in Dulbecco's Modified Eagle's Medium supplemented with 5% fetal bovine serum (FBS) for amplification and then the amplified adenovirus was purified by a 11 chromatographic method. This procedure is illustrated in Figure 8.

12 [0062] As illustrated in Figure 9, the expression of Hu1A4A1 IgG1 -furin or Hu1A4A1lgG1-2A was 13 achieved by first infecting HEK 293 cells with the recombinant adenovirus pAd-Hu1A4A1IgG1-furin 14 or pAd-Hu1A4A1IgG1-2A at a multiplicity of infection (MOI) of 1. The infected cells were cultured for one week and the culture supernatant was harvested. The expressed Hu1A4A1IgG1-furin or 16 Hu1A4A1IgG1-2A was purified using protein L agarose gel from Pierce (Brockville, Ont., Canada).
17 Briefly, culture supernatant was dialyzed against phosphate buffer saline (PBS) (Sigma-Aldrich, 18 Oakville, Ont., Canada) for 12h and then concentrated using PEG (Sigma-Aldrich) to less than 50 19 ml. The concentrated sample was incubated with 2m1 protein L agarose gel at 4 C for 1 h. The gel and supernatant mixture was then loaded to an empty column, which was subsequently washed with 21 binding buffer. Bound Hu1A4A1IgG1-furin or Hu1A4A1lgG1-2A was eluted with elution buffer. The 22 eluted Ab was further desalted using an excellulose column (Pierce) and then concentrated by a 23 CentraconTM YM-30 (Millipore Corp., Bedford, MA, USA).

24 [0063] The amino acid sequence of the expressed Hu1A4A1IgG1-furin is shown in SEQ ID
NO:12 and the amino acid sequence of the expressed Hu1A4A1IgG1-2A is shown in SEQ ID NO:14.
26 [0064] Cells that were transformed to express the Hu1A4A1IgG1-furin and Hu1A4A1IgG1-2A
27 humanized antibodies have been deposited at the International Depositary Authority of Canada 28 (IDAC) (National Microbiology Laboratory, Winnipeg, Manitoba, Canada) under accession numbers 29 141107-01 and 141107-02, respectively.

[0065] SDS-PAGE

31 [0066] Abs were separated by 10% SDS-PAGE gels using a Mini-PROTEAN TM II
apparatus 32 (Bio-Rad Laboratories, Mississauga, Ont., Canada). The bands were visualized by SimplyBlueTM
33 safestain staining (Invitrogen, Burlington, Ont., Canada). The molecular weights of the samples 21989275.1 10 Agent Ref: 67853/00022 1 were estimated by comparison to the relative mobility values of standards of known molecular 2 weights. The SDS-PAGE analyses of the purified Hu1A4A1IgG1-furin are illustrated in Figures 10 3 and 11. Figure 12 illustrates the SDS-PAGE analysis of the purified Hu1A4A1IgG1-2A. As shown, 4 lanes 1 and 3 correspond to purified Hu1A4A1IgG1 and control human IgG1 in a non-reducing condition and lanes 2 and 4 correspond to purified Hu1A4A1IgG1 and control human IgG1 in a 6 reducing condition.

7 [0067] ELISA

8 [0068] The reactivity of purified Hu1A4A1IgG1-furin or Hu1A4A1IgG1-2A to VEEV E2 antigen 9 was determined by ELISA. Nunc MaxisorpTM flat bottomed 96-well plates (Canadian Life Technologies, Burlington, Ont., Canada) were coated overnight at 4 C with recombinant VEEV E2 11 antigen at a concentration of 10pg/ml in carbonate bicarbonate buffer, pH
9.6. The plates were 12 washed five times with PBS containing 0.1 % TweenTM-20 (PBST) and then blocked in 2% bovine 13 serum albumin for 2h at room temperature. After five washes with PBST, the plates were incubated 14 for 2h at room temperature with various concentrations of Hu1A4A1IgG1-furin, Hu1A4A1IgG1-2A or 1A4A1 Abs diluted in PBST. Following five washes with PBST, the plates were incubated for 2h at 16 room temperature with horseradish peroxidase (HRP)-conjugated rabbit anti-human IgG fragment 17 crystallizable portion or HRP-conjugated rabbit anti-mouse IgG (Jackson ImmunoResearch 18 Laboratories Inc., West Grove, PA, USA) diluted 1:5000 in PBST. Finally, the plates were washed 19 five times with PBST and developed for 10 min at room temperature with a 3,3',5,5'-tetramethylbenzidine substrate (Kirkegaard and Perry Laboratories). The reactions were read at an 21 absorbance of 650 nm by a microplate autoreader (Molecular Devices, Sunnyvale, CA, USA). The 22 results of the ELISA Hu1A4A1IgG1-antigen binding assay are illustrated in Figure 13.

23 [0069] Neutralization assay in vitro 24 [0070] Neutralizing activity of each of Hu1A4A1IgG1-furin and Hu1A4A1IgG1-2A against VEEV
(strain TC-83) was analyzed by a plaque reduction assay. Briefly, each Ab was serially two-fold 26 diluted (1:32, 1:64, 1:128, etc.) and mixed with an equal volume containing 50 plaque-forming units 27 of virus per 100 pl. Afterwards, the mixtures were incubated for 1 h at room temperature, 200 pl of 28 the mixture was inoculated in duplicate into wells of six-well plates containing confluent Vero cell 29 monolayers and incubated at 37 C for 1 h. At the end of the incubation, the virus/Ab mixtures were removed from the wells before the wells were overlaid by tragacanth gum and then incubated for 2 31 days. The wells were stained with 0.3% crystal violet and plaques were counted. Neutralization titre 32 was expressed as the highest Ab dilution that inhibited 50% of virus plaques. This procedure is 33 illustrated in Figure 15.

21989275.1 11 Agent Ref: 67853/00022 1 [0071] Results and Discussion 2 [0072] Different approaches have been developed to humanize murine Abs in order to reduce 3 the antigenicity of murine Abs in humans [9,10]. One widely used approach is CDR-grafting, which 4 involves the grafting of all murine CDRs onto a human Ab frameworks. The human Ab frameworks are chosen based on their similarities to the frameworks of the murine Ab to be humanized. The 6 CDR-grafting approach has been proven successful in some cases. However, in many more 7 instances, this humanization process could result in CDR conformation changes, which affect the 8 antigen-binding affinity. To restore the affinity, additional work for back-mutation of several murine 9 framework amino acids, which are deemed to be critical for CDR loop conformation, have to be done.

11 [0073] Recently, Hwang et al. [12] employed an approach which consisted of grafting CDRs 12 onto human germline Ab frameworks based on the CDR sequence similarities between the murine 13 and human Abs while basically ignoring the frameworks. Because the selection of the human 14 frameworks is driven by the sequence of the CDRs, this strategy minimizes the differences between the murine and human CDRs. This approach has the potential to generate humanized Abs that 16 retain their binding affinity to their cognate antigen. Further, since all residues in frameworks are 17 from human Ab germline sequences, the potential immunogenicity of non-human Abs is highly 18 reduced.

19 [0074] Using the above approach, and as disclosed herein, the present inventors humanized an anti-VEEV murine mAb 1A4A1. The amino acid sequences of VH and VL from murine 1A4A1 were 21 first aligned with human Ig germline V and J genes. As shown in Figure 5, the human heavy chain V
22 gene segment H5-51 and J gene segment JH4 were selected to provide the frameworks for the 23 murine 1A4A1 VH. Similarly, as shown in Figure 6, for the murine 1A4A1 VL, the human light chain 24 V gene segment L15 and J gene segment Jk3 were selected.

[0075] The identities of the CDR1 and CDR2 amino acid sequences between murine 26 and the human H5-51 gene segment were 20% and 47%, respectively, while the identity of the 27 CDR3 between murine 1A4A1 VH and the JH4 gene segment was 33%. For the light chain, the 28 identities of the CDR1 and CDR2 between murine 1A4A1 VL and the human L15 gene segment 29 were 27% and 14%, respectively, while the identity of the CDR3 between murine 1A4A1 VL and human Jk3 gene segment was 22%. The CDRs of murine 1A4A1 VH were then grafted onto the 31 frameworks of selected human Ig germline H5-51 and JH4 gene segments, while the CDRs of 32 murine 1A4A1 VL were grafted onto human L15 and Jk3 gene segments. The hu1A4A1 VH was 33 further grafted onto the human gamma 1 heavy chain CHs to form a complete heavy chain, while the 21989275.1 12 Agent Ref: 67853/00022 1 VL was grafted onto the human kappa 1 light chain CL to form a whole humanized light chain. This 2 procedure is schematically illustrated in Figures 5 and 6 with the end structure being illustrated in 3 Figure 7.

4 [0076] As shown in Figure 5, the murine 1A4A1 VH CDRs grafted onto the human framework comprised the following amino acid sequences:

6 VH CDR1: DYHVH (SEQ ID NO: 1) 7 VH CDR2: MTYPGFDNTNYSETFKG (SEQ ID NO: 2) 8 VH CDR3: GVGLDY (SEQ ID NO: 3) 9 [0077] As shown in Figure 6, the murine 1A4A1 VL CDRs grafted onto the human framework comprised the following amino acid sequences:

11 VL CDR1: KASQDVDTAVG (SEQ ID NO: 4) 12 VL CDR2: WSSTRHT (SEQ ID NO: 5) 13 VL CDR3: HQYSSYPFT (SEQ ID NO: 6) 14 [0078] As shown in Figure 5, the VH of the humanized Ab according to the present invention comprises the following amino acid sequence:

16 Hu-VH:

18 KGQVTISADKSISTAYLQWSSLKASDTAMYYCARGVGLDYWGQGTLVTVSS (SEQ ID NO: 7).

19 [0079] Thus, as shown in Figure 6, the VL of the humanized Ab according to the present invention comprises the following amino acid sequence:

21 Hu-VL:

23 GVPSRFSGSGSGTDFTLTISSLQPEDFATYYCHQYSSYPFTFGPGTKVDIKR (SEQ ID NO: 8).
24 [0080] In order to express heavy and light chains in a monocistronic construct, a six-residue peptide, RGRKRR (SEQ ID NO: 9) containing the recognition site for the protease furin, designated 26 as "furin linker", or a twenty-four-residue peptide of the foot-and-mouth-disease virus (FMDV)-27 derived 2A self-processing sequence, APVKQTLNFDLLKLAGDVESNPGP (SEQ ID NO:
10), 21989275.1 13 Agent Ref: 67853/00022 1 designated as "2A linker", was incorporated between the two chains. The location of the furin or 2A
2 linker within the nucleic acid constructs of the Abs is illustrated in Figure 7. Furin is a ubiquitous 3 subtilisin-like proprotein convertase, which is the major processing enzyme of the secretory pathway 4 [13]. The furin minimal cleavage site is R-X-X-R; however, the enzyme prefers the site R-X-(K/R)-R. An additional R at the P6 position appears to enhance cleavage. The FMDV-derived 2A
6 linker is able to cleave at its own C terminus between the last two residues through an enzyme-7 independent but undefined mechanism, probably by ribosomal skip, during protein translation. To 8 get the expressed Ab to be secreted to culture media, a leader sequence was added upstream to 9 the Ab gene. Figure 7 illustrates the synthesized DNA sequence, of approximately 2 kb, including the human Ab kappa light chain L15 leader sequence, the humanized light chain (VL + CL), the furin 11 or 2A linker, and the humanized heavy chain (VH + CH1 + CH2 + CH3). This sequence was then 12 cloned into an adenoviral vector. The unique restriction sites, as also shown in Figure 7, flanking the 13 V regions, which allow for efficient V region replacement and at the heavy chain V-C region junction 14 for generation of fragment antigen-binding portion of Ab (Fab), were also designed.

[0081] Protein G and A columns are widely used for a quick purification for Abs because of 16 protein G and A binding to the Fc portion of Ig. However, protein G and A
cannot only bind to 17 human Ig, but also bind to bovine Ig, therefore they cannot be used for purification of Hu1A4A1IgG1-18 furin or Hu1A4A1IgG1-2A in our study since pAd-Hu1A4A1IgG1-furin or pAd-Hu1A4A1IgG1-2A-19 infected HEK 293 cells were cultured in the medium with 5% FBS containing a high percentage of bovine Ig. Unlike protein G and A, protein L binds Ig through interactions with the light chains.
21 Protein L only binds to Ig containing light chains of type kappa 1, 3 and 4 in human and kappa 1 in 22 mouse. Most importantly, protein L does not bind to bovine Ig. Since our humanized Ab has human 23 kappa 1 chain, we chose a protein L column to purify Hu1A4A1IgG1-furin or Hu1A4A1IgG1-2A to 24 eliminate co-purification of bovine Ig. In this way, the purity of Hu1A4A1IgG1-furin or Hu1A4A1IgG1-2A was relatively high in SDS-PAGE as shown in Figures 10, 11 and 12.

26 [0082] When the purified product was subjected to 10% SDS-PAGE, Hu1A4A1IgG1-furin and 27 Hu1A4A1IgG1-2A showed up in a different way. As illustrated in Figure 12, Hu1A4A1IgGI-2A
28 showed the same patterns as a control human IgG1, one band of -150kDa in non-reducing condition 29 (intact disulfide bridges) and two bands, 50kDa for heavy chains and 25kDa for light chains (broken disulfide bridges) in reducing condition, indicating that the 2A linker underwent self-processing 31 perfectly. On the other hand, Hu1A4A1IgG1-furin showed only one clear band of -75kDa in 32 reducing condition observed as illustrated in Figures 10 and 11, indicating that the furin linker was 33 not cleaved. However, in another study (data not shown), the same furin linker sequence was 34 cleaved in another Fab construct expressed in a mammalian system. This indicated the 21989275.1 14 Agent Ref: 67853/00022 1 conformation of expressed Hu1A4A1 IgG1-furin probably rendered the furin linker inaccessible to 2 furin or that the sequence surrounding the furin linker influenced furin cleavage.

3 [0083] The specific binding reactivities of purified Hu1A4A1IgG1-furin and Hu1A4A1lgG1-2A to 4 VEEV E2 antigen were examined by ELISA. As illustrated in Figure 13, both versions of the Hu1A4A1 IgG1 were found to bind to VEEV E2 in a dose-dependent manner, similar to the binding to 6 VEEV E2 of its parental murine 1A4A1, indicating this non-cleaved Ab was still reactive to VEEV E2 7 antigen in ELISA. Furthermore, both versions were evaluated for their ability to block VEEV infection 8 in Vero cells using a standard plaque-reduction assay. The Hu1A4A1IgG1-fruin showed a 9 neutralizing activity with 50% plaque reduction neutralization titre at 0.78 pg/mi, whereas Hu1A4A1IgG1-2A showed a much higher neutralization titre at 0.1 pg/ml.

11 [0084] From the above results, it is concluded that the murine 1A4A1 Ab was successfully 12 humanized. As illustrated in Figure 14, the expressed and purified Ab of Hu1A4A11gG1-2A was 13 cleaved between the heavy and light chains as expected; however, Hu1A4A1IgG1-furin was not 14 cleaved. Nevertheless, the present inventors have exhibited that both versions of the Hu1A4A1IgG1 retained the antigen binding specificity and virus neutralizing activity.
Thus, the Hu1A4A1IgG1-furin 16 or Hu1A4A1IgG1-2A discussed and characterized herein would serve as an effective prophylactic 17 and therapeutic agent against VEEV infection.

18 [0085] Example 2: In vivo study - Protection or pre-exposure prophylaxis of mice from 19 VEEV challenge by passive immunization with Hu1A4A1IgG1-furin or HuIA4A1IgG1-2A
[0086] Materials and methods 21 [0087] Passive immunization (Pre-exposure prophylaxis) 22 [0088] Balb/c mice aged 6-8 weeks were injected intraperitoneally (i.p) with 50 pg of 23 Hu1A4A1IgG1-furin or Hu1A4A1IgG1-2A in 100 pl PBS, human IgG in 100 pl PBS
(positive control) 24 or 100 pl PBS alone (negative control) 24 h prior to VEEV challenge.

[0089] VEEV challenge 26 [0090] Each mouse was challenged subcutaneously (s.c.) with 30-50 plaque forming units (pfu) 27 of virulent VEEV (Trinidad donkey, TRD) in 50 pl of Leibovitz L15 maintenance medium (L15MM) 24 28 h after passive immunization. The challenge dose approximated to 100 x 50%
lethal dose (LD50).
29 Mice were examined frequently for signs of illness for 14 days, and humane endpoints were used.

21989275.1 15 Agent Ref: 67853/00022 1 [0091] Results 2 [0092] Hu1A4A1IgG1-furin or HuIA4A11gG1-2A clearance in mice 3 [0093] To determine the half-life of Hu1A4A1IgG1-furin or Hu1A4A1lgG1-2A in mouse serum, 4 groups of 4 mice, were injected i.p. with 50 pg, each mouse, of either Hu1A4A1IgG1-furin or Hu1A4A1IgG1-2A, or human anti-VEEV IgG and bled from the vein at increasing time intervals after 6 injection. The quantity of Ab present in serum samples was estimated by immunoassay.
7 Hu1A4A1IgG1-furin or Hu1A4A1IgG1-2A had a similar half-life as human anti-VEEV IgG, around 10 8 days.

9 [0094] Protection of mice from VEEV challenge by passive immunization with Hu1A4A1IgG1-furin or Hu1A4A1IgG1-2A

11 [0095] Groups of 8 mice were injected i.p. with the Hu1A4A1IgG1-furin, Hu1A4A1lgG1-2A, 12 human IgG (positive control) or PBS alone (negative control) and 24h later challenged s.c. with 100 13 x LD50 of VEEV. None of the mice treated only with human IgG (positive control) or PBS alone 14 (negative control) survived. All the Hu1A4A1IgG1-furin or Hu1A4A1lgG1-2A
treated mice survived the VEEV challenge without any clinical signs at 14 days post-challenge.

16 [0096] Discussion 17 [0097] Passive immunization of the Hu1A4AI IgG1-furin or Hu1A4A1IgG1-2A in mice (50 18 pg/mouse) 24 h before virulent VEEV challenge provided 100% protection against 100xLD50 19 challenge of VEEV when mice were treated with 50 pg/each mouse of Hu1A4A1IgG1-furin or Hu1A4A1 IgG1-2A. The mice were also found to be asymptomatic throughout the 14 day 21 observation period. These results indicate that the humanized anti-VEEV
rAbs of the present 22 invention have pre-exposure prophylactic capacity against VEEV infections.
The half-lives of the 23 humanized anti-VEEV rAbs in mice was around 10 days suggesting that the humanized anti-VEEV
24 rAbs of the invention would be an effective prophylactic against VEEV for at least several weeks.
Thus, the rAbs of the invention have been demonstrated to have functionality as an immunization 26 agent against VEEV infection.

21989275.1 16 Agent Ref: 67853/00022 1 [0098] Example 3: In vivo study - Treatment or post-exposure therapy of mice after VEEV
2 challenge by passive immunization with Hu1A4A1IgG1-furin or Hu1A4A1IgG1-2A

3 [0099] Materials and methods 4 [00100] Post-exposure Therapy [00101] Balb/c mice aged 6-8 weeks were challenged s.c. with 100 x LD50 of virulent VEEV in 6 50 p1 of L15MM per mouse. At 24 h post-challenge, mice were injected i.p with 50 lag of 7 Hu1A4A1IgG1-furin or Hu1A4A1IgG1-2A in 100 pl PBS, or 100 pl PBS alone. Mice were examined 8 frequently for signs of illness for 20 days, and humane endpoints were used.

9 [00102] Results [00103] The half-lives of Hu1A4A1IgG1-furin or Hu1A4A1IgG1-2A was determined above in 11 Example 2.

12 [00104] Treatment of mice after VEEV challenge using Hu1A4A1IgG1-furin or Hu1A4A1lgG1-2A
13 [00105] Groups of 8 mice were challenged s.c. with 100 x LD50 of VEEV.
Twenty-four hours 14 later, the infected mice were administered i.p. with Hu1A4A1IgG1-furin, Hu1A4A1IgG1-2A or PBS
alone (50 ug/mouse). All the Hu1A4A1IgG1-2A-treated mice survived throughout the observation 16 period (20 days post-challenge) with minor clinical signs. All Hu1A4A1lgG1-furin or PBS-treated 17 mice died.

18 [00106] Discussion 19 [00107] Passive immunization of the Hu1A4A1IgG1-2A in mice (50 lag/mouse) 24 h after virulent VEEV challenge provided 100% protection against 100xLD50 challenge of VEEV
with only minor 21 clinical signs, indicating the Hu1A4A1IgG1-2A has post-exposure therapeutic capacity against VEEV
22 infections. Unfortunately, Hu1A4A1IgG1-furin did not show any post-exposure therapy capacity.
23 One possible reason for this finding may be that the antigen binding capacity of uncut 24 Hu1A4A1 IgG 1 -furin is inferior to the cleaved Hu1A4A1IgG1-2A.

26 [00108] Bibliography 27 [00109] One or more of the following documents have been referred to in the present disclosure.
28 The following documents are incorporated herein by reference in their entirety.

21989275.1 17 Agent Ref: 67853/00022 1 [00110] [1] Weaver SC, Ferro C, Barrera R, Boshell J, Navarro JC. Venezuelan equine 2 encephalitis. Annu Rev Entomol, 2004;49:141-74.

3 [00111] [2] Rivas F, Diaz LA, Cardenas VM, Daza E, Bruzon L, Alcala A, et al. Epidemic 4 Venezuelan equine encephalitis in La Guajira, Colombia, 1995. J Infect Dis, 1997;175:828-32.

[00112] [3] Pittman PR, Makuch RS, Mangiafico JA, Cannon TL, Gibbs PH, Peters CJ. Long-term 6 duration of detectable neutralizing antibodies after administration of live-attenuated VEE vaccine and 7 following booster vaccination with inactivated VEE vaccine. Vaccine, 1996;
14:337-43.

8 [00113] [4] Jahrling PB, Stephenson EH. Protective efficacies of live attenuated and 9 formaldehyde-inactivated Venezuelan equine encephalitis virus vaccines against aerosol challenge in hamsters. J Clin Microbiol, 1984; 19:429-31.

11 [00114] [5] France JK, Wyrick BC, Trent DW. Biochemical and antigenic comparison of the 12 envelope glycoproteins of Venezuelan equine encephalomyelitis virus strains. J Gen Virol, 1979;
13 44:725-40.

14 [00115] [6] Roehrig JT, Day JW, Kinney RM. Antigenic analysis of the surface glycoproteins of a Venezuelan equine encephalomyelitis virus (TC-83) using monoclonal antibodies.
Virology, 16 1982;118:269-78.

17 [00116] [7] Roehrig JT, Mathews JH. The neutralization site on the E2 glycoprotein of 18 Venezuelan equine encephalomyelitis (TC-83) virus is composed of multiple conformationally stable 19 epitopes. Virology, 1985; 142:347-56.

[00117] [8] Schroff RW, Foon KA, Beatty SM, Oldham RK, Morgan Jr AC. Human anti-murine 21 immunoglobulin responses in patients receiving monoclonal antibody therapy.
Cancer Res, 1985;
22 45:879-85.

23 [00118] [9] Verhoeyen M, Milstein C, Winter G. Reshaping human antibodies:
grafting an 24 antilysozyme activity. Science, 1988; 239:1534-6.

[00119] [10] Dall'Acqua WF, Damschroder MM, Zhang J, Woods RM, Widjaja L, Yu J, et al.
26 Antibody humanization by framework shuffling. Methods, 2005; 36:43-60.

27 [00120] [11] Hu WG, Alvi AZ, Fulton RE, Suresh MR, Nagata LE. Genetic engineering of 28 streptavidin-binding peptide tagged single-chain variable fragment antibody to Venezuelan equine 29 encephalitis virus. Hybrid Hybridomics, 2002; 21:415-20.

21989275.1 18 Agent Ref: 67853/00022 1 [00121] [12] Hwang WY, Almagro JC, Buss TN, Tan P, Foote J. Use of human germline genes in 2 a CDR homology-based approach to antibody humanization. Methods, 2005; 36:35-42.

3 [00122] [13] van den Ouweland AM, van Duijnhoven HL, Keizer GD, Dorssers LC, Van de Ven 4 WJ. Structural homology between the human fur gene product and the subtilisin-like protease encoded by yeast KEX2. Nucleic Acids Res, 1990; 18:664.

6 (00123] [14] Fulton RE, Nagata, L, Alvi, A; US Patent No. 6,818,748, Nov.
16, 2004.

7 [00124] [15] Johnson KM, Martin DH. Venezuelan equine encephalitis. Adv. Vet Sci Comp Med.
8 1974; 18(0):79-116.

9 [00125] [16] Groot H, The health and economic importance of Venezuelan equine encephalitis (VEE) in Venezuelan encephalitis, Scientific publication no, 243, 1972, pp. 7-16, Pan American 11 Health Organization, Washington DC.

12 [00126] [17] Phillpotts RJ, Jones LD, Howard SC, Monoclonal antibody protects mice against 13 infection and disease when given either before or up to 24h after airborne challenge with virulent 14 Venezuelan equine encephalitis virus. Vaccine, 2002 Feb 22; 20 (11-12):
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(00127] [18] Hu WG, Chau D, Wu J, Jager S, Nagata L, Humanization and mammalian 16 expression of murine monoclonal antibody against Venezuelan equine encephalitis virus. Vaccine, 17 2007; 25:3210-3214.

19 [00128] Although the invention has been described with reference to certain specific embodiments, various modifications thereof will be apparent to those skilled in the art without 21 departing from the purpose and scope of the invention as outlined in the claims appended hereto.
22 Any examples provided herein are included solely for the purpose of illustrating the invention and are 23 not intended to limit the invention in any way. Any drawings provided herein are solely for the 24 purpose of illustrating various aspects of the invention and are not intended to be drawn to scale or to limit the invention in any way. The disclosures of all prior art recited herein are incorporated 26 herein by reference in their entirety.

21989275.1 19

Claims (23)

1. A use of a humanized recombinant antibody in the prophylaxis or treatment against infection from Venezuelan equine encephalitis virus, VEEV, in a mammal, wherein said antibody comprises a human Ig framework and having grafted thereon complementarity determining regions, CDRs, from the murine monoclonal antibody 1A4A1.

2. The use according to claim 1 wherein said antibody has specificity to VEEV.

3. The use according to claim 2 wherein said antibody has specificity to an epitope of the E2 envelope protein of VEEV.

4. The use according to claim 3 wherein said epitope is E2c.

5. The use according to claim 1 wherein said antibody has heavy chain variable region (VH) complementarity determining regions CDR1, CDR2 and CDR3 comprising the following amino acid sequences:
CDR1: SEQ ID NO: 1 CDR2: SEQ ID NO: 2 CDR3: SEQ ID NO: 3.

6. The use according to claim I wherein said antibody has light chain variable region (VL) complementarity determining regions CDR1, CDR2 and CDR3 comprising the following amino acid sequences:
CDR1: SEQ ID NO: 4 CDR2: SEQ ID NO: 5 CDR3: SEQ ID NO: 6.

7. The use according to claim 1 wherein said antibody has a VH comprising an amino acid sequence according to SEQ ID NO: 7.

8. The use according to claim 1 wherein said antibody has a VL comprising an amino acid sequence according to SEQ ID NO: 8.

9. The use according to any one of claims 1 to 8 wherein said antibody has an amino acid sequence according to SEQ ID NO: 12.

10. The use according to any one of claims 1 to 8 wherein said antibody has an amino acid sequence according to SEQ ID NO: 14.

11. The use according to any one of claims 1 to 8 wherein said antibody is encoded by a nucleic acid sequence according to SEQ ID NO: 11.

12. The use according to any one of claims 1 to 8 wherein said antibody is encoded by a nucleic acid sequence according to SEQ ID NO: 13.

13. The use according to any one of claims 1 to 12 wherein said antibody is encoded by an expression vector.

14. The use according to any one of claims 1 to 12 wherein said antibody is expressed by a transformed host cell.

15. A method of preventing or treating VEEV infection in a mammal comprising administering to said mammal a humanized recombinant antibody comprises a human Ig framework and having grafted thereon complementarity determining regions, CDRs, from the murine monoclonal antibody 1 A4A 1.

16. The method according to claim 15 wherein said antibody has heavy chain variable region (VH) complementarity determining regions CDR1, CDR2 and CDR3 comprising the following amino acid sequences:
CDR1: SEQ ID NO: 1 CDR2: SEQ ID NO: 2 CDR3: SEQ ID NO: 3.

17. The method according to claim 15 wherein said antibody has light chain variable region (VL) complementarity determining regions CDR1, CDR2 and CDR3 comprising the following amino acid sequences:
CDR1: SEQ ID NO: 4 CDR2: SEQ ID NO: 5 CDR3: SEQ ID NO: 6.

18. The method according to claim 15 wherein said antibody has a VH comprising an amino acid sequence according to SEQ ID NO: 7.

19. The method according to claim 15 wherein said antibody has a VL comprising an amino acid sequence according to SEQ ID NO: 8.

20. The method according to claim 15 wherein said antibody has an amino acid sequence according to SEQ ID NO: 12 or SEQ ID NO: 14.

21. The method according to claim 15 wherein said antibody is encoded by a nucleic acid sequence according to SEQ ID NO: 11 or SEQ ID NO: 13.

22. The method according to claim 15 wherein said antibody is encoded by an expression vector.

23. The method according to claim 15 wherein said antibody is expressed by a transformed host cell.