TARGETING ANTIGEN INTO THE PHAGOCYTIC PATHWAY IN-VIVO INDUCES PROTECTIVE TUMOR-IMMUNITY

Cytotoxic T lymphocytes (CTLs) kill neoplastic or virally infected cel ls after recognizing on their surface antigenic peptides bound to majo r histocompatibility complex class molecules. These peptides are deriv ed from antigens that are degraded in the cytosol of the affected cell . Because exogenous proteins cannot enter the cytosol, immunizations w ith killed pathogens or their proteins do not generally elicit CTLs. H owever, antigens that are internalized into phagocytic cells can enter the cytosol and be processed for class presentation. Here we show tha t immunization with a purified antigen on an avidly phagocytized parti cle primes CTLs, which in turn protect animals from subsequent challen ge with tumours transfected with the antigen gene. Interestingly, thes e animals also become immune to other antigens expressed by the tumour . This approach could be exploited to develop tumour and viral vaccine s.