Development of a Novel Vaccine Against Herpes Simplex Type 2

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DESCRIPTION (provided by applicant): Herpes simplex virus type 2 (HSV-2) is a medically important pathogen worldwide, with a prevalence rate of over 20% in the US. The physical pain and psychosocial stress due to recurrent herpetic genital lesions have provided a strong impetus for the development of an efficacious vaccine. However, the HSV-2 vaccines tested in clinical trials to date have shown only limited benefits. Defining the immune correlates of an effective vaccine is particularly challenging since the natural immunity to HSV-2 is not sufficient to protect against recurrent infection and viral shedding. Thus, immune responses generated by a successful vaccine must be more effective than natural immunity. Recent studies of the natural immunity to another herpesvirus, murine cytomegalovirus (MCMV), have demonstrated that CD8 T cells specific for an immunodominant MCMV antigen are ineffective at limiting viral replication. This suggests that the herpesviruses skew the host T cell response in order to make dominant the specificities that favor viral persistence rather than clearance. We hypothesize that the essential, nonstructural proteins that are highly conserved among the herpesviruses may represent a novel class of T cell targets due to the requirements for their expression and sequence stability. Of particular importance, our recent results show that DNA immunization using either of two conserved, essential genes of MCMV protects mice against MCMV replication. In this grant application, we propose to accomplish the following aims: In Specific Aim 1, we will quickly identify which of the conserved, essential genes of HSV-2 are protective by DNA vaccination in a mouse model, and the optimal combination of protective genes and glycoprotein D2 (gD2) DNA will be determined. In Specific Aim 2, we will extend our findings into the guinea pig model so that protection can be measured against both primary and recurrent HSV-2 infection. The immunity and protection generated by the optimal combination of conserved, essential HSV-2 genes and gD2 DNA will be compared to the gD2/MPL/alum protein subunit vaccine that was partially protective in clinical testing. In Specific Aim 3, we will test in guinea pigs whether the DNA mediated protection can be augmented by subsequent boosting with a novel combination of whole, killed virus plus the MPL/alum adjuvants, a boost that will likely elicit virus specific Th1 and neutralizing antibody responses. The overall goal of this proposal is to demonstrate "proof-of-principle" that the conserved, essential genes of HSV-2 are also protective against HSV-2 in animal models and to provide the justification for pursuing more comprehensive preclinical studies of immunity and protection using this novel class of antigens. Herpes simplex virus type 2 (HSV-2) causes a lifelong, persistent infection that results in the development of recurrent genital lesions that can cause both physical pain and emotional stress. In addition, transmission of the virus during birth can cause a devastating disease in the newborn, and genital HSV-2 infection has been found to be a significant risk factor for infection with HIV. The high prevalence of infection in the U.S. population together with the medical and psychological impacts of the disease make HSV-2 an important candidate for the development of an effective vaccine that can prevent infection or disease.