HEAT-SHOCK FUSION PROTEINS AS VEHICLES FOR ANTIGEN DELIVERY INTO THE MAJOR HISTOCOMPATIBILITY COMPLEX CLASS-I PRESENTATION PATHWAY

Mice immunized with heat shock proteins (hsps) isolated from mouse tum or cells (donor cells) produce CD8 cytotoxic T lymphocytes (CTL) that recognize donor cell peptides in association with the major histocompa tibility complex (MHC) class I proteins of the responding mouse. The C TL are induced apparently because peptides noncovalently associated wi th the isolated hsp molecules can enter the MHC class I antigen proces sing pathway of professional antigen-presenting cells, Using a recombi nant heat shock fusion protein with a large fragment of ovalbumin cova lently linked to mycobacterial hsp70, we show here that when the solub le fusion protein was injected without adjuvant into H-2(b) mice, CTL were produced that recognized an ovalbumin-derived peptide, SIINFEKL, in association with K-b. The peptide is known to arise from natural pr ocessing of ovalbumin in H-2(b) mouse cells, and CTL from the ovalbumi n-hsp70-immunized mice and a highly effective CTL clone (4G3) raised a gainst ovalbumln-expressing EL4 tumor cells (EG7-OVA) were equally eff ective in terms of the concentration of SIINFEKL required for half-max imal lysis in a CTL assay, The mice were also protected against lethal challenge with ovalbumin-expressing melanoma tumor cells, Because lar ge protein fragments or whole proteins serving as fusion partners can be cleaved into short peptides in the MHC class I processing pathway, hsp fusion proteins of the type described here are promising candidate s for vaccines aimed at eliciting CD8 CTL in populations of MHC-dispar ate individuals.