INDUCTION OF MUCOSAL IMMUNITY AGAINST HERPES-SIMPLEX VIRUS BY PLASMIDDNA IMMUNIZATION

The ability of mucosally delivered plasmid DNA encoding glycoprotein B (gB) of herpes simplex virus type 1 (HSV-1) to generate systemic as w ell as distal mucosal immunity was evaluated. BALB/c mice were immuniz ed intranasally (i.n.) with gB DNA or DNA expressing beta-galactosidas e (beta-Gal). Two days following immunization, gB and beta-Gal gene ex pression was detected by reverse transcription (RT)-PCR in lungs and c ervical lymph nodes (CLN). Histological analysis showed that beta-Gal protein was expressed in vivo in the lungs and the CLN of animals immu nized with i.n. administered beta-Gal DNA. The immune responses genera ted by i.n. administration of gB DNA with or without cholera toxin (CT ) were compared to those generated by intramuscular (i.m.) gB DNA and i.n. live HSV administration. Three i.n. doses of gB DNA over a 3-week period resulted in a distal mucosal immunoglobulin A (IgA) response, In addition, the mucosal IgA response was enhanced by coadministration of CT with gB DNA. The i.m. route of immunization induced a strong Ig G response in the serum and vagina but was inefficient in generating a mucosal IgA response. Antigen specific cytokine ELISPOT analyses as w ell as the serum IgG1/IgG2a ratio indicated induction of stronger Th2 responses following the additional i.n. administration of CT compared to i.n. or i.m. gB DNA or i.n. live HSV immunization. In addition, muc osal immunization with gB DNA induced anti-HSV cell-mediated immunity in vivo as measured by delayed-type hypersensitivity. Although i.n. DN A immunization was an effectively means of inducing mucosal antibody, it was inferior to i.m. DNA delivery in providing protection against l ethal HSV challenge,in the vaginal route. In addition, both i.m. and i .n. plasmid immunizations failed to generate an immune barrier to vira l invasion of the mucosa.