Immune response to caprine arthritis-encephalitis virus surface protein induced by coimmunization with recombinant vaccinia viruses expressing the caprine arthritis-encephalitis virus envelope gene and caprine interleukin-12

The objective of this study was to determine if interleukin (IL)-12 can foc us an antigen specific type 1 immune response characterized by activation o f Th1 lymphocytes and production of IgG2 antibodies in vivo. Saanen goats c o-immunized with recombinant vaccinia viruses expressing caprine IL-12 (rRB -IL12) and the caprine arthritis-encephalitis virus (CAEV) envelope (env) g ene (rWR-63) were evaluated for development of immune responses to the CAEV env encoded surface glycoprotein (SU). Immune responses were de-fined by: (i) SU antibody titers; (ii) the ratio of SU IgG1 and IgG2 antibodies; (iii ) interferon gamma (IFN gamma) and IL-4 gene expression and proliferative r esponse of SU stimulated lymph node mononuclear cells (LNMC). Apart from en hancement of IFN gamma and IL-4 gene expression in SU stimulated LNMC, rRB- IL12 did not affect the immune response to rWR-63 encoded SU. Thus, localiz ed production of exogenous species specific IL-12 at the site of immunizati on did not focus initial priming of antigen reactive Th lymphocytes. These results are in contrast to previous studies using inbred mice and raise que stions regarding the use of cytokine adjuvants to focus immune responses in outbred animals, (C) 2000 Elsevier Science Ltd. All rights reserved.