Active Antiviral T-Lymphocyte Response Can Be Redirected against Tumor Cells by Antitumor Antibody × MHC/Viral Peptide Conjugates

Abstract

Purpose:To redirect an ongoing antiviralT-cell response against tumor cells in vivo, we evaluated conjugates consisting of antitumor antibody fragments coupled to class I MHC molecules loaded with immunodominant viral peptides. Experimental Design: First, lymphochoriomeningitis virus (LCMV)^infected C57BL/6 mice were s.c. grafted on the right flank with carcinoembryonic antigen (CEA)^transfected MC38 colon carcinoma cells precoated with anti-CEA  H-2D b /GP33 LCMV peptide conjugate and on the left flank with the same cells precoated with control anti-CEA F(ab ¶) 2 fragments. Second, influenza virus^infected mice were injected i.v., to induce lung metastases, with HER2-transfected B16F10 cells, coated with either anti-HER2  H-2D b /NP366 influenza peptide conjugates, or anti-HER2 F(ab ¶) 2 fragments alone, or intact anti-HER2 monoclonal antibody. Third, systemic injections of anti-CEA  H-2D b conjugates with covalently cross-linked GP33 peptides were tested for the growth inhibition of MC38-CEA + cells, s.c. grafted in LCMV-infected mice.Results: In the LCMV-infected mice, five of the six grafts with conjugate-precoated MC38-CEA + cells did not develop into tumors, whereas all grafts with F(ab ¶) 2 -precoated MC38-CEA + cells did so (P = 0.0022). In influenza virus^infected mice, the group injected with cells precoated with specific conjugate had seven times less lung metastases than control groups (P = 0.0022 and P = 0.013). Most importantly, systemic injection in LCMV-infected mice of anti-CEA  H-2D b /cross-linked GP33 conjugates completely abolished tumor growth in four of five mice, whereas the same tumor grew in all five control mice (P = 0.016). Conclusion:The results show that a physiologic T-cell antiviral response in immunocompetent mice can be redirected against tumor cells by the use of antitumor antibody  MHC/viral peptide conjugates.In recent years, a major effort has been dedicated to the development of active vaccination protocols for immunotherapy of cancer patients, using newly discovered tumor-specific or differentiation antigens (1 -3). Successful induction of specific T-cell responses and tumor infiltration by T lymphocytes were well documented, but the number of tumor remissions remained low (4,5). It is hard to understand the reasons for the relatively poor antitumor activity of the induced specific T lymphocytes, given that such effector cells are known to be so efficient in the elimination of virus-infected cells and in allograft rejection. Three major explanations have been given for the inefficiency of the T-cell antitumor response: the poor antigenicity of autologous tumor antigens, the low expression or absence of MHC molecules on the tumor cell surface, or some functional defects in their antigen-processing machinery (6, 7).Here, we present a new immunotherapeutic strategy that has the potential to overcome these obstacles. We coupled an antitumor antibody fragment to an MHC molecule loaded with an immunodominant viral peptide and showed that tumor cells coated with the...

Sustained activation and tumor targeting of NKT cells using a CD1d–anti-HER2–scFv fusion protein induce antitumor effects in mice

“…The α3 domain of CD1d was interrupted before the transmembrane region, and a small linker (G 3 S 3 ) was inserted, followed by a His tag for purification (His 6 ) ( Figure 1A). In addition, to confer the tumor localization properties of the αGalCer/ sCD1d, we fused the β 2 m-CD1d molecule to an antitumor antibody fragment in view of our previous experience with tumor targeting of MHC class I coupled to different antitumor Fab′ fragments (25,26). To do so, a second (G 10 S 3 ) linker was inserted at the C-terminus of CD1d before ligation to the cDNA of the anti-HER2 4D5 scFv (27), followed by the same small linker (G 3 S 3 ) and His tag ( Figure 1A).…”

“…Such bifunctional molecules were able to redirect an ongoing antiviral T cell response against cancer cells in vivo (25,26). Here we developed a similar strategy applied to CD1d fused to the anti-HER2 scFv 4D5 with the aim to redirect iNKT cells to HER2-expressing tumor cells.…”

Committing Cytomegalovirus-Specific CD8 T Cells to Eliminate Tumor Cells by Bifunctional Major Histocompatibility Class I Antibody Fusion Molecules

“…Mimicking a viral infection specifically in tumor cells and thus redirecting preexisting virus-specific effector T cells to attack tumors would overcome several limitations for immune control of cancer. First, the viral antigen is clearly nonself and thus able to trigger high-affinity T cells (19,20). Second, the antibodymediated delivery of virus-peptide-loaded MHC class I complexes (pMHCI) to tumors would overcome the problem of downregulation of MHCI expression observed with variable frequencies in different tumor types (21).…”

A New Class of Bifunctional Major Histocompatibility Class I Antibody Fusion Molecules to Redirect CD8 T Cells

“…However, these constructs were lacking FcRn-binding properties and as a consequence were rapidly cleared and had short in vivo half-lives. An alternative was to generate the pMHCI complex and the antibody separately and fuse both of them by chemical conjugation or by biotin-streptavidin coupling (14,22,(41)(42)(43)(44)(45). Chemical conjugation is technically laborious especially at a larger scale and sitespecific conjugation is not fully developed yet.…”

“…In addition, the a-chain contains a transmembrane domain anchoring the complex to the cell surface (12). We and others have previously shown that antibody-mediated targeting of peptide-MHC class I complexes can decorate tumor cells with antigenic peptides, thus rendering them similar to virally infected cells and triggering elimination of these cells by CD8 þ cytotoxic T cells (13)(14)(15). We found in the previous study that human PBMCs with low frequencies of CMV-specific CD8 þ T cells (<1%) were still sufficient to eliminate targeted tumor cells effectively (15).…”