Enhanced immunogenicity of a functional enzyme by T cell epitope modification

Hartley strain guinea pig T cell epitopes were mapped for two related bacterial proteases. Two T cell epitopes were found in one of the proteases, while a comparatively reduced immunogenicity protease had no detectable T cell epitopes. A T cell epitope sequence homologous to the immunogenic protease was created in the less immunogenic protease by changing a single amino acid. Proliferative responses to the whole protein parent enzyme were two-fold higher in splenocyte cultures from variant-immunized animals. We found that the single amino acid change in the variant resulted in a protein immunogen that induced higher titers of antigen-specific IgG antibody at low doses and at early time points during the immunization protocol. The serum from parent- and variant-immunized guinea pigs cross-reacted at both the protein and the peptide level. Finally, animals primed to the variant but boosted with the parent enzyme had higher levels of antigen-specific IgG than animals immunized with the parent enzyme alone.With a single amino acid change we have introduced a T cell epitope into a comparatively low-immunogenic enzyme and have increased its immunogenicity while retaining the enzyme's original proteolytic function. The ability to immunomodulate proteins while leaving their function intact has important implication for the development of recombinant vaccines and protein-based therapeutics.High affinity humoral immune responses to most protein antigens require cognate interactions between antigen-specific T and B cells. Antigen-specific T cells encounter antigen presented by dendritic cells that migrate to the paracortical regions of draining lymph nodes after initial antigen contact [1]. Only dendritic cells have the capacity to induce activation in resting peripheral T cells [2,3]. Once activated, differentiated T helper cells contact antigen-specific B cells and provide signals for B cell differentiation via CD154-CD40 interactions, as well as by the production of cytokin