Mucosal and systemic immune responses induced after oral delivery of vaccinia virus recombinants

The immune responses elicited after oral delivery of vaccinia virus (VV) recombinants are not well defined. In this study we show with mice, that after oral administration of a VV recombinant expressing the luciferase reporter gene, VV gene expression takes place for several days in gut-associated lymphoid (GALT) tissues as well as in the spleen. After 14 days, a significant mucosal IgA response against VV was detected in vaginal and intestinal washings, as well as a systemic specific IgG response, which was principally of the IgG2a subclass. Furthermore, orally immunized mice developed cellular immune responses to VV (CD8+ T cells and T helper activities) in mesenteric lymph nodes (MLN) and spleen. Oral immunization with a VV recombinant expressing, either the envelope protein of HIV or beta-galactosidase, induced a specific immune response, locally and systemically, against gp120 and beta-gal. The cytokine pattern found in supernatants of spleen and MLN cells after stimulation with VV antigens or gp120 was clearly of type 1 cytokines. These studies demonstrate that VV recombinants administered by the oral route generate mucosal and systemic immune responses against antigens of the virus vector and to the recombinant products. These observations are of significance in the use of poxvirus vectors as vaccines.