A chemically induced vaccine strategy for prostate cancer.

Here we report the design and evaluation of a bifunctional, small molecule switch that induces a targeted immune response against tumors in vivo. A high affinity ligand for prostate specific membrane antigen (PSMA) was conjugated to a hapten that binds dinitrophenyl (DNP)-specific antibodies. When introduced into hu-PBL-NOD/SCID mice previously immunized with a KLH-DNP immunogen, this conjugate induced a targeted antibody-dependent cellular cytotoxicity (ADCC) response to PSMA-expressing tumor cells in a mouse xenograft model. The ability to create a small molecule inducible antibody response against self-antigens using endogenous non-autoreactive antibodies may provide advantages over the autologous immune response generated by conventional vaccines in certain therapeutic settings.

Loss of CD4 T-cell-dependent tolerance to proteins with modified amino acids.

The site-specific incorporation of the unnatural amino acid p-nitrophenylalanine (pNO(2)Phe) into autologous proteins overcomes self-tolerance and induces a long-lasting polyclonal IgG antibody response. To determine the molecular mechanism by which such simple modifications to amino acids are able to induce autoantibodies, we incorporated pNO(2)Phe, sulfotyrosine (SO(3)Tyr), and 3-nitrotyrosine (3NO(2)Tyr) at specific sites in murine TNF-α and EGF. A subset of TNF-α and EGF mutants with these nitrated or sulfated residues is highly immunogenic and induces antibodies against the unaltered native protein. Analysis of the immune response to the TNF-α mutants in different strains of mice that are congenic for the H-2 locus indicates that CD4 T-cell recognition is necessary for autoantibody production. IFN-γ ELISPOT analysis of CD4 T cells isolated from vaccinated mice demonstrates that peptides with mutated residues, but not the wild-type residues, are recognized. Immunization of these peptides revealed that a CD4 repertoire exists for the mutated peptides but is lacking for the wild-type peptides and that the mutated residues are processed, loaded, and presented on the I-A(b) molecule. Overall, our results illustrate that, although autoantibodies are generated against the endogenous protein, CD4 cells are activated through a neo-epitope recognition mechanism. Therefore, tolerance is maintained at a CD4 level but is broken at the level of antibody production. Finally, these results suggest that naturally occurring posttranslational modifications such as nitration may play a role in antibody-mediated autoimmune disorders.