INTERLEUKIN-5 EXPRESSED BY A RECOMBINANT VIRUS VECTOR ENHANCES SPECIFIC MUCOSAL IGA RESPONSES IN-VIVO

Several in vitro studies have shown that murine interleukin-5 (mIL-5) enhances IgA production by activated mucosal B cells. To date, however , there is no evidence that this factor significantly up-regulates muc osal IgA responses in vivo. Here, we show that expression of the gene for mIL-5 in a recombinant vaccinia virus vector markedly increases Ig A responses to co-expressed heterologous antigen in the lungs of mice given intranasal inocula of the virus. The elevated local IgA response s to vectors expressing mIL-5 peaked at a fourfold higher level than t hose elicited by control virus at 14 days after infection and were sus tained for at least 4 weeks. Increased IgA responses were abrogated in mice treated with monoclonal antibody against mIL-5 and were not dete cted in systemic lymphoid tissue. No enhancement of specific IgG level s was found either locally or systemically. Our results indicate that mIL-5 selectively enhances the development of mucosal IgA responses in vivo and suggest that expression of this factor in mucosal vaccine ve ctors may stimulate local immune reactivity.