The longterm goal of this project is to utilize cytomegalovirus (CMV) vectors in the development of a therapeutic vaccine against herpes simplex virus 2 (HSV-2), the causative agent of genital herpes. HSV-2 is widely prevalent in the population causing recurrent genital lesions and significantly increasing the risk for other sexually transmitted diseases such as HIV. Despite this unmet medical need, there is no approved vaccine for HSV-2. While some vaccine approaches have shown promise in preclinical studies, they failed to protect individuals from de novo or recurrent infection in clincal trials. Given the known role of T lymphocytes in limiting HSV-2 reactivation and the associated development of lesions, a successful HSV-2 vaccine needs to induce and maintain a strong T cell response that effectively identifies and neutralizes infected cells. CMV vectors are uniquely qualified for this task due to their ability to induce lifelong, high frequency effector memory T cll (TEM) responses. The TEM cell population is maintained by persistent, low level antigen presentation thus generating a continuous immune shield in peripheral sites of pathogen entry as well as internal sites of spreading and reactivation. In non-human primate models, TEM induced by CMV-vectored vaccines have shown unprecedented protection against simian immunodeficiency viruses, including when challenged intra- vaginally. In fact, protected animals are functionally cured, suggesting a long-term therapeutic effect of CMV- based vaccines. CMV-vectors are therefore currently being developed for prophylactic and therapeutic vaccines against HIV by the founders of TomegaVax. In the human population, CMV is highly prevalent establishing lifelong persistent infection that is asymptomatic. Unlike traditional viral vectors, CMV vectors can be used repeatedly and without any loss to immunogenicity or efficacy even in individuals already harboring persistent CMV infection. Importantly, spread-deficient CMV vectors maintain the same level of TEM stimulation as wildtype vectors thus providing safe and effective vectors even for immunocompromised recipients. To demonstrate the feasibility of using CMV vectors as HSV-2 vaccines we propose to evaluate spread-deficient murine CMV vectors expressing HSV-2 antigens in a well-established murine model. Using bacterial artificial chromosome technology and innovative complementation methods, we will construct wild- type and spread-deficient CMV vectors expressing selected HSV antigens. We will monitor and characterize in detail the immune responses induced by CMV vectors to these antigens and determine their ability to protect against lethal challenge with HSV-2. This phase I study will enable the selection of protective HSV antigens for insertion into spread-deficient human CMV vectors. Phase II of this program will then focus on IND-enabling studies to manufacture and test HCMV-vectored HSV vaccines. The ultimate product of this research program will be a recombinant therapeutic vaccine providing lifelong protection against recurring genital herpes.
The ultimate goal of this project is to develop a vaccine against herpes simplex virus type-2 (HSV-2). Unlike other vaccines in development, our approach will generate a persistent immune shield against reactivating HSV-2. In this proof of concept study we will generate and test recombinant CMV-strains that produce an immunogenic response to the HSV-2 payload antigens ICP0 and ICP4.
