Immunogenicity, protective efficacy, and non-replicative status of the HSV-2 vaccine candidate HSV529 in mice and guinea pigs

HSV-2 vaccine is needed to prevent genital disease, latent infection, and virus transmission. A replication-deficient mutant virus (dl5-29) has demonstrated promising efficacy in animal models of genital herpes. However, the immunogenicity, protective efficacy, and non-replicative status of the highly purified clinical vaccine candidate (HSV529) derived from dl5-29 have not been evaluated. Humoral and cellular immune responses were measured in mice and guinea pigs immunized with HSV529. Protection against acute and recurrent genital herpes, mortality, latent infection, and viral shedding after vaginal HSV-2 infection was determined in mice or in naïve and HSV-1 seropositive guinea pigs. HSV529 replication and pathogenicity were investigated in three sensitive models of virus replication: severe combined immunodeficient (SCID/Beige) mice inoculated by the intramuscular route, suckling mice inoculated by the intracranial route, and vaginally-inoculated guinea pigs. HSV529 immunization induced HSV-2-neutralizing antibody production in mice and guinea pigs. In mice, it induced production of specific HSV-2 antibodies and splenocytes secreting IFNγ or IL-5. Immunization effectively prevented HSV-2 infection in all three animal models by reducing mortality, acute genital disease severity and frequency, and viral shedding. It also reduced ganglionic viral latency and recurrent disease in naïve and HSV-1 seropositive guinea pigs. HSV529 replication/propagation was not detected in the muscles of SCID/Beige mice, in the brains of suckling mice, or in vaginal secretions of inoculated guinea pigs. These results confirm the non-replicative status, as well as its immunogenicity and efficacy in mice and guinea pigs, including HSV-1 seropositive guinea pigs. In mice, HSV529 produced Th1/Th2 characteristic immune response thought to be necessary for an effective vaccine. These results further support the clinical investigation of HSV529 in human subjects as a prophylactic vaccine.

Comparison of parenteral delivery routes of ACAM529, a replication-defective vaccine against genital herpes (106.24)

Human herpes simplex viruses (HSV types 1 and 2) constitute the primary cause of genital ulcer disease. Genital herpes is the most prevalent sexually transmitted infection and is found throughout the world. Available treatments for HSV-infected patients are not 100% effective and cannot prevent acquisition of infection. ACAM529 is an HSV-2 virus made replication-defective by deletion of the genes UL5 and UL29. ACAM529 is propagated in a complementing cell line expressing the deleted genes (Da Costa et al., J. Virol.2000). Here we present the comparison of three routes of administration of ACAM529. We measured immunogenicity as well as protective efficacy in the mouse vaginal challenge model. ELISA and neutralizing antibody titers, as well as protection against morbidity, mortality and viral shedding of the challenge virus indicate that two doses of ACAM529 delivered intramuscularly are optimal.