Herpesvirus Pathogenesis and Vaccine Development

National Institute Of Allergy And Infectious Diseases

Investigators

Linked publications, trials & patents

Abstract

Over 90% of adults are infected with EBV. Epstein-Barr virus (EBV) causes infectious mononucleosis and is associated with a number of B cell and epithelial cell cancers including Burkitt lymphoma, Hodgkin lymphoma, nasopharyngeal carcinoma, and gastric carcinoma. EBV is also associated with post-transplant lymphoproliferative disease and severe disease in patients with X-linked lymphoproliferative disease; no therapies are approved to prevent EBV infection in these patients. Human cytomegalovirus (HCMV) infects over half of the human population and is the most common infectious cause of birth defects. At present there are no licensed vaccines for either EBV or HCMV and hyperimmune globulin to HCMV has been of limited usefulness for prophylaxis or therapy of HCMV infections, while no such antibody product exists for EBV. Previously we designed a nanoparticle vaccine consisting of a single-chain EBV glycoprotein H (gH) and glycoprotein L (gL) or a single chain gH/gL and glycoprotein 42 (gH/gL/gp42) that were each fused to bacterial ferritin to form a self-assembling nanoparticle. Structural analysis revealed that single-chain gH/gL and gH/gL/gp42 adopted a similar conformation to the wild-type glycoproteins, and the glycoprotein spikes were observed by electron microscopy. These vaccines elicited neutralizing antibodies in mice, ferrets, and nonhuman primates that inhibited EBV entry into both B cells and epithelial cells. When mixed with a previously reported gp350 nanoparticle vaccine no immune competition was observed. To confirm the efficacy of the EBV vaccines in vivo, humanized mice were challenged with EBV after passive transfer of IgG from mice vaccinated with control, gH/gL/gp42+gp350, or gH/gL+gp350 nanoparticles. Although all control animals were infected, only one mouse in each vaccine group that received immune IgG had detectable transient viremia. Furthermore, no EBV lymphomas were detected in immune animals. This bivalent EBV nanoparticle vaccine represents a promising candidate to prevent EBV infection and EBV-related malignancies in humans. The EBV gH/gL glycoprotein complex facilitates fusion of the virus membrane with host cells and is a target of neutralizing antibodies. In 2023, we examined the sites of vulnerability for virus neutralization and fusion inhibition within EBV gH/gL. We developed a panel of human monoclonal antibodies (mAbs) that targeted five distinct antigenic sites on EBV gH/gL and prevented infection of epithelial and B cells. Structural analyses using X-ray crystallography and electron microscopy revealed multiple sites of vulnerability and defined the antigenic landscape of EBV gH/gL. One mAb provided near-complete protection against viremia and lymphoma in a humanized mouse EBV challenge model. Our findings provide structural and antigenic knowledge of the viral fusion machinery, yield a potential therapeutic antibody to prevent EBV disease, and emphasize gH/gL as a target for herpesvirus vaccines and therapeutics.