COVALENT LINKAGE OF IL-12 AND OVALBUMIN CONFINES THE EFFECTS OF IL-12TO OVALBUMIN-SPECIFIC IMMUNE-RESPONSES

In order to direct the form of the immune response in an antigen-speci fic manner, we constructed a fusion protein (OVA/IL12) that contained the T cell-dependent antigen, ovalbumin (OVA), covalently linked to mu rine interleukin-12 (IL-12). The OVA/IL12 protein was produced in a ba culovirus expression system and was purified by anti-OVA immunoaffinit y chromatography. The purified OVA/IL12 protein displayed patent IL-12 bioactivity in an IL-12 proliferation assay. BALB/c mice immunized wi th the OVA/IL12 protein produced increased quantities of anti-OVA IgG2 a antibody compared with mice immunized with recombinant OVA alone. Ly mph node cells from the immunized mice with the OVA/IL12 protein produ ced large amounts of IFN-gamma when restimulated in vitro with OVA, wh ile those from mice immunized with the OVA protein produced little or no IFN-gamma. In contrast, immunization with a mixture of OVA and free recombinant IL-12 also induced IFN-gamma production, which was not OV A-specific. These studies indicate that the OVA/IL12 fusion protein ca n induce OVA-specific, Th1-dominated immune responses, and that the co valent linkage of OVA and IL-12 confines the effect of IL-12 to OVA-sp ecific cells.