Soluble Rhesus Lymphocryptovirus gp350 Protects against Infection and Reduces Viral Loads in Animals that Become Infected with Virus after Challenge

Abstract

Epstein-Barr virus (EBV) is a human lymphocryptovirus that is associated with several malignancies. Elevated EBV DNA in the blood is observed in transplant recipients prior to, and at the time of post-transplant lymphoproliferative disease; thus, a vaccine that either prevents EBV infection or lowers the viral load might reduce certain EBV malignancies. Two major approaches have been suggested for an EBV vaccine- immunization with either EBV glycoprotein 350 (gp350) or EBV latency proteins (e.g. EBV nuclear antigens [EBNAs]). No comparative trials, however, have been performed. Rhesus lymphocryptovirus (LCV) encodes a homolog for each gene in EBV and infection of monkeys reproduces the clinical, immunologic, and virologic features of both acute and latent EBV infection. We vaccinated rhesus monkeys at 0, 4 and 12 weeks with (a) soluble rhesus LCV gp350, (b) virus-like replicon particles (VRPs) expressing rhesus LCV gp350, (c) VRPs expressing rhesus LCV gp350, EBNA-3A, and EBNA-3B, or (d) PBS. Animals vaccinated with soluble gp350 produced higher levels of antibody to the glycoprotein than those vaccinated with VRPs expressing gp350. Animals vaccinated with VRPs expressing EBNA-3A and EBNA-3B developed LCV-specific CD4 and CD8 T cell immunity to these proteins, while VRPs expressing gp350 did not induce detectable T cell immunity to gp350. After challenge with rhesus LCV, animals vaccinated with soluble rhesus LCV gp350 had the best level of protection against infection based on seroconversion, viral DNA, and viral RNA in the blood after challenge. Surprisingly, animals vaccinated with gp350 that became infected had the lowest LCV DNA loads in the blood at 23 months after challenge. These studies indicate that gp350 is critical for both protection against infection with rhesus LCV and for reducing the viral load in animals that become infected after challenge. Our results suggest that additional trials with soluble EBV gp350 alone, or in combination with other EBV proteins, should be considered to reduce EBV infection or virus-associated malignancies in humans.

High Levels of Antibody that Neutralize B-cell Infection of Epstein–Barr Virus and that Bind EBV gp350 Are Associated with a Lower Risk of Nasopharyngeal Carcinoma

“…A previous study in non-human primates showed that rhesus gp350 vaccinated animals with higher levels of anti-gp350 antibody were not always protected from rhesus EBV primary infection compared to controls but did have lower levels of EBV DNA in the blood years after infection. (36) Since EBV-infected B-cells are thought to traffic to the oropharynx where the virus is shed, anti-gp350 and B-cell neutralizing antibodies may lessen an individual’s cumulative exposure to EBV at mucosal sites including the nasopharynx, thereby reducing the risk of developing NPC. Further, infection of B-cells in vitro with EBV results in a large percentage of virus remaining on the surface of the cells, and this virus can efficiently infect epithelial cells;(37) thus, antibodies that neutralize B-cell infection might reduce transfer of EBV from B-cells to epithelial cells.…”

Expression and immunogenic characterization of recombinant gp350 for developing a subunit vaccine against Epstein-Barr virus

“…In a previous study, virus-like replicon particle expressing gp350 (VRP-gp350) elicited low levels of antibodies to gp350 (Sashihara et al 2011). Compared with VRP-gp350, the recombinant gp350 1-443 induced higher levels of anti-gp350 1-443 antibodies, indicating the strong immunogenicity of the yeast-expressed recombinant protein.…”

“…Increasing numbers of observations indicated that immunization with gp350 could provide Electronic supplementary material The online version of this article (doi:10.1007/s00253-015-7027-x) contains supplementary material, which is available to authorized users. protection from EBV-induced lymphomas in animal models (Finerty et al 1992(Finerty et al , 1994Sashihara et al 2011). Results from the first clinical trial showed that gp350-based vaccination elicited neutralizing antibodies and protected the subjects from EBV infection (Gu et al 1995).…”

The Development of Prophylactic and Therapeutic EBV Vaccines

“…Despite the similarities with EBV, rhesus LCV does not induce the immortalisation of B cells in vitro, although it has been associated with lymphoma development in immunocompromised macaques. Studies by Cohen and colleagues have investigated the impact of both antibody and T cell-based vaccines on rhesus LCV infection (Sashihara et al 2011). Immunisation with rhesus gp350 was shown to be protective against viral challenge, reducing viral load following infection and seroconversion to LCV viral capsid antigen.…”