Enhancement of mucosal IgA responses by interleukins 5 and 6 encoded in recombinant vaccine vectors.

The expression of the genes for murine interleukin-5 (IL-5) or IL-6 in recombinant vaccinia virus vectors markedly increased IgA reactivity to co-expressed heterologous antigen in the lungs of mice inoculated intranasally with the viruses. These elevated local IgA responses reached a peak four times higher than those elicited by control viruses 14 days after infection and these peak levels were maintained for at least four weeks. Elevated IgA responses, reaching a peak 3-4 weeks after immunization, were also observed in the lungs of mice inoculated with IL-6 expressed by another vector, fowlpox virus. The results indicate that these factors enhance the development of mucosal IgA reactivity in vivo and suggest that their expression in mucosal vaccine vectors may stimulate local immune responses. The approach described in this study may be useful in stimulating mucosal immunity to a wide range of vector-encoded antigens, not only for vaccination against disease but also for immunocontraception by the co-expression of antigens involved in reproduction.