Epstein-Barr virus (EBV), a γ-herpesvirus, is the first identified oncogenic virus, which establishes permanent infection in humans. EBV causes infectious mononucleosis and is also tightly linked to many malignant diseases. Various vaccine formulations underwent testing in different animals or in humans. However, none of them was able to prevent EBV infection and no vaccine has been approved to date. Current efforts focus on antigen selection, combination, and design to improve the efficacy of vaccines. EBV glycoproteins such as gH/gL, gp42, and gB show excellent immunogenicity in preclinical studies compared to the previously favored gp350 antigen. Combinations of multiple EBV proteins in various vaccine designs become more attractive approaches considering the complex life cycle and complicated infection mechanisms of EBV. Besides, rationally designed vaccines such as virus-like particles (VLPs) and protein scaffold-based vaccines elicited more potent immune responses than soluble antigens. In addition, humanized mice, rabbits, as well as nonhuman primates that can be infected by EBV significantly aid vaccine development. Innovative vaccine design approaches, including polymer-based nanoparticles, the development of effective adjuvants, and antibody-guided vaccine design, will further enhance the immunogenicity of vaccine candidates. In this review, we will summarize (i) the disease burden caused by EBV and the necessity of developing an EBV vaccine; (ii) previous EBV vaccine studies and available animal models; (iii) future trends of EBV vaccines, including activation of cellular immune responses, novel immunogen design, heterologous prime-boost approach, induction of mucosal immunity, application of nanoparticle delivery system, and modern adjuvant development.

Epstein-Barr virus (EBV) infects more than 90% of the world’s adult population and accounts for a significant cancer burden of epithelial and B cell origins. Glycoprotein B (gB) is the primary fusogen essential for EBV entry into host cells. Here, we isolated two EBV gB-specific neutralizing antibodies, 3A3 and 3A5; both effectively neutralized the dual-tropic EBV infection of B and epithelial cells. In humanized mice, both antibodies showed effective protection from EBV-induced lymphoproliferative disorders. Cryoelectron microscopy analyses identified that 3A3 and 3A5 bind to nonoverlapping sites on domains D-II and D-IV, respectively. Structure-based mutagenesis revealed that 3A3 and 3A5 inhibit membrane fusion through different mechanisms involving the interference with gB-cell interaction and gB activation. Importantly, the 3A3 and 3A5 epitopes are major targets of protective gB-specific neutralizing antibodies elicited by natural EBV infection in humans, providing potential targets for antiviral therapies and vaccines.

Herpesviruses are among the most successful viruses found in human populations. They establish lifelong latent infections, which are punctuated by recurrent reactivations. The entry process of herpesviruses into specific target cells requires a well-orchestrated teamwork involving multiple envelope glycoproteins. The conserved glycoprotein B (gB) is the membrane fusogen, of which conformational changes are induced by an entry complex (EC) consisting of at least gH and gL. Despite the high prevalence and heavy disease burdens associated with human herpesviruses (HHVs), vaccines against these pathogens are still lacking, except for varicella zoster virus (VZV). Recent advances in understanding the coordinated mechanisms of action of the key EC glycoproteins and fusogen will help to improve approaches for effective vaccine development and neutralizing antibody (nAb) screening.

Nasopharyngeal carcinoma (NPC) is an Epstein–Barr virus (EBV)–associated epithelial malignancy characterized by the presence of prominent infiltration of lymphocytes, including natural killer (NK) cells. Although NK cells can directly target EBV-infected tumor cells without restriction by the MHC, EBV-positive (EBV+) NPC cells often develop resistance mechanisms that allow them to evade immune surveillance by NK cells. Elucidating the mechanisms involved in EBV-induced NK-cell dysfunction will contribute to the design of novel NK cell–based immunotherapies to treat NPC. Herein, we confirmed that the cytotoxic function of NK cells was impaired in EBV+ NPC tissues and found that EBV infection–induced expression of B7-H3 in NPC negatively correlated with NK-cell function. The inhibitory effect of EBV+ tumor expression of B7-H3 on NK-cell function was clarified in vitro and in vivo. Mechanistically, activation of the PI3K/AKT/mTOR signaling pathway via EBV latent membrane protein 1 (LMP1) was responsible for EBV infection–induced upregulation of B7-H3 expression. In an NPC xenograft mouse model with adoptive transfer of primary NK cells, deletion of B7-H3 on tumor cells in combination with anti–PD-L1 treatment restored NK cell–mediated antitumor activity and significantly improved the antitumor efficacy of NK cells. On the basis of our findings, we conclude that EBV infection can inhibit NK cell–mediated antitumor function by inducing upregulation of B7-H3 expression and provide a rationale for NK cell–based immunotherapies in combination of PD-L1 blockade and overcoming the immunosuppression of B7-H3 to treat EBV-associated NPC.