A multivalent prophylactic and therapeutic vaccine against EBV infection and EBV-associated malignancies

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ABSTRACT: Epstein-Barr virus (EBV) represents a major global health problem, as it is associated with infectious mononucleosis in adolescents and >200,000 pediatric and adult cancer cases worldwide each year. Despite the high morbidity and mortality associated with EBV infection, there is no licensed prophylactic EBV vaccine. Thus, a safe and effective EBV prophylactic vaccine is urgently needed. To date, no vaccine candidate has elicited neutralizing antibodies (nAbs) to completely block EBV infection in vivo. Approaches to EBV vaccine development have been limited in part by the oncogenic potential of the viral genome and a lack of animal models to test vaccine candidates. This proposed project will use a novel strategy to develop a safe and effective vaccine candidate that incorporates up to five EBV glycoproteins into a single Epstein-Barr virus- like particle (EBV-LP). The EBV glycoproteins gp350, gB, gp42, and gH/gL complex, which are essential for EBV attachment, fusion, and entry into host cells, are attractive targets for provoking a humoral/antibody- mediated response. Our group and others have shown that antibodies to these glycoproteins neutralize viral infection in vitro and in vivo. Thus, their inclusion is critical for developing an effective prophylactic vaccine that protects against viral infection. To our knowledge, this combination of EBV antigens has not been tested in pre- clinical or clinical trials. We will generate EBV-LPs containing combinations of up to five glycoproteins using modified vaccinia Ankara virus. We will determine the efficacy of the EBV-LPs to generate nAb responses in wild-type mice, then test the ability of these antibodies to neutralize >90% of EBV infection of human epithelial and B cells in vitro and to prevent infection of human B cells in vivo in a humanized mouse model (Aim 1). Because EBV is human-tropic, we will use the EBV-homologous rhesus lymphocryptovirus (rhLCV) as a surrogate virus to study vaccine efficacy in vivo in rhesus macaques (RM), considered the most relevant animal model that recapitulates key features of human EBV infection. Importantly, RM orally inoculated with rhLCV exhibit acute symptoms and viral shedding similar to EBV+ humans, as well as development of lymphoma after persistent infection under immunosuppression. We will evaluate the ability of our EBV-LP- based or analogous rhLCV-LP-based vaccines to elicit nAbs that can prevent or limit infection, with no/low EBV DNA in blood, splenocytes, or lymph nodes, and absence of EBV+ cancer in immunocompetent and immunocompromised RM, compared to well-characterized EBV gp350-based vaccines (Aim 2). Our central hypothesis is that EBV-LPs/rhLCV-LPs will generate protective anti-EBV/rhLCV glycoprotein nAb responses to prevent EBV/rhLCV infection in vitro and in vivo. We expect our approach to provide a path to an investigational new drug application for a prophylactic EBV vaccine. We will also define, for the first time, the minimum EBV/rhLCV glycoproteins required to elicit sterilizing nAbs in vitro and in vivo. This will advance our long-term goal of developing vaccines that prevent EBV infection and EBV-associated diseases and cancers.