MODULATION OF IMMUNOGENICITY AND ANTIGENICITY OF PROTEINS BY MALEYLATION TO TARGET SCAVENGER RECEPTORS ON MACROPHAGES

We have maleylated proteins to target macrophage-specific scavenger re ceptors and have used this system to study changes in the epitopes and immunogenicity of such proteins. We show that maleylation of diphther ia toroid (DT) induces targeting to macrophage scavenger receptors and enhances its immunogenicity. DT does not evoke detectable serum Ab re sponses upon injection as soluble protein. However, maleylated DT (mDT ) does generate a significant Ab response. Furthermore, immunization w ith soluble mDT leads to a better T cell proliferative response in vit ro than immunization with DT can generate, thereby demonstrating that maleylation leads to enhanced T cell immunogenicity in vivo. We also f ind that maleylation disrupts the native B cell epitopes of DT and cre ates new epitopes, because antisera to DT and mDT do not cross-react. At least some of the new epitopes generated are maleylation specific, because antisera against various maleylated proteins do cross-react. I n contrast, maleylation does not significantly modify the repertoire o f T cell epitopes generated from DT, because T eel Is generated by eit her DT or mDT immunization are cross-reactive, and both DT and mDT can stimulate T cells that are specific for a single synthetic DT peptide . Maleylated proteins are better presented in vitro than are their nat ive counterparts, and this enhancement of presentation is blocked by u nrelated maleylated proteins. These results suggest that Ags targeted to scavenger receptors on macrophages by maleylation are better presen ted to T cells and are immunogenic in vivo without adjuvant.