T cell epitope screening of Epstein-Barr virus fusion protein gB

A cocktail nanovaccine targeting key entry glycoproteins elicits high neutralizing antibody levels against EBV infection

Epstein-Barr virus (EBV) infects more than 95% of adults worldwide and is closely associated with various malignancies. Considering the complex life cycle of EBV, developing vaccines targeting key entry glycoproteins to elicit robust and durable adaptive immune responses may provide better protection. EBV gHgL-, gB- and gp42-specific antibodies in healthy EBV carriers contributed to sera neutralizing abilities in vitro, indicating that they are potential antigen candidates. To enhance the immunogenicity of these antigens, we formulate three nanovaccines by co-delivering molecular adjuvants (CpG and MPLA) and antigens (gHgL, gB or gp42). These nanovaccines induce robust humoral and cellular responses through efficient activation of dendritic cells and germinal center response. Importantly, these nanovaccines generate high levels of neutralizing antibodies recognizing vulnerable sites of all three antigens. IgGs induced by a cocktail vaccine containing three nanovaccines confer superior protection from lethal EBV challenge in female humanized mice compared to IgG elicited by individual NP-gHgL, NP-gB and NP-gp42. Importantly, serum antibodies elicited by cocktail nanovaccine immunization confer durable protection against EBV-associated lymphoma. Overall, the cocktail nanovaccine shows robust immunogenicity and is a promising candidate for further clinical trials.

Identification of HLA-A*11:01 and A*02:01-Restricted EBV Peptides Using HLA Peptidomics

Epstein-Barr Virus (EBV) is closely linked to nasopharyngeal carcinoma (NPC), notably prevalent in southern China. Although type II latency of EBV plays a crucial role in the development of NPC, some lytic genes and intermittent reactivation are also critical for viral propagation and tumor progression. Since T cell-mediated immunity is effective in targeted killing of EBV-positive cells, it is important to identify EBV-derived peptides presented by highly prevalent human leukocyte antigen class I (HLA-I) molecules throughout the EBV life cycle. Here, we constructed an EBV-positive NPC cell model to evaluate the presentation of EBV lytic phase peptides on streptavidin-tagged specific HLA-I molecules. Utilizing a mass spectrometry (LC-MS/MS)-based immunopeptidomic approach, we characterized eleven novel EBV peptides as well as two previously identified peptides. Furthermore, we determined these peptides were immunogenic and could stimulate PBMCs from EBV VCA/NA-IgA positive donors in an NPC endemic southern Chinese population. Overall, this work demonstrates that highly prevalent HLA-I-specific EBV peptides can be captured and functionally presented to elicit immune responses in an in vitro model, which provides insight into the epitopes presented during EBV lytic cycle and reactivation. It expands the range of viral targets for potential NPC early diagnosis and treatment.

T cell-mediated immunity during Epstein-Barr virus infections in children

Epstein-Barr virus (EBV) infection is extremely common worldwide, with approximately 90% of adults testing positive for EBV antibodies. Human are susceptible to EBV infection, and primary EBV infection typically occurs early in life. EBV infection can cause infectious mononucleosis (IM) as well as some severe non-neoplastic diseases, such as chronic active EBV infection (CAEBV) and EBV-associated hemophagocytic lymphohistiocytosis (EBV-HLH), which can have a heavy disease burden. After primary EBV infection, individuals develop robust EBV-specific T cell immune responses, with EBV-specific CD8⁺ and part of CD4⁺ T cells functioning as cytotoxic T cells, defending against virus. Different proteins expressed during EBV's lytic replication and latent proliferation can cause varying degrees of cellular immune responses. Strong T cell immunity plays a key role in controlling infection by decreasing viral load and eliminating infected cells. However, the virus persists as latent infection in EBV healthy carriers even with robust T cell immune response. When reactivated, it undergoes lytic replication and then transmits virions to a new host. Currently, the relationship between the pathogenesis of lymphoproliferative diseases and the adaptive immune system is still not fully clarified and needs to be explored in the future. Investigating the T cell immune responses evoked by EBV and utilizing this knowledge to design promising prophylactic vaccines are urgent issues for future research due to the importance of T cell immunity.

Immunotherapeutic approaches in EBV-associated nasopharyngeal carcinoma

Epstein-Barr virus (EBV) was the first tumor virus in humans. Nasopharyngeal carcinoma (NPC) accounts for approximately 60% of the 200,000 new tumor cases caused by EBV infection worldwide each year. NPC has an insidious onset and is highly malignant, with more than 70% of patients having intermediate to advanced disease at the time of initial diagnosis, and is strongly implicated in epithelial cancers as well as malignant lymphoid and natural killer/T cell lymphomas. Over 90% of patients with confirmed undifferentiated NPC are infected with EBV. In recent decades, much progress has been made in understanding the molecular mechanisms of NPC and developing therapeutic approaches. Radiotherapy and chemotherapy are the main treatment options for NPC; however, they have a limited efficacy in patients with locally advanced or distant metastatic tumors. Tumor immunotherapy, including vaccination, adoptive cell therapy, and immune checkpoint blockade, represents a promising therapeutic approach for NPC. Significant breakthroughs have recently been made in the application of immunotherapy for patients with recurrent or metastatic NPC (RM-NPC), indicating a broad prospect for NPC immunotherapy. Here, we review important research findings regarding immunotherapy for NPC patients and provide insights for future research.

Vesicular Stomatitis Virus-Based Epstein-Barr Virus Vaccines Elicit Strong Protective Immune Responses

Epstein-Barr virus (EBV), the first identified human tumor virus, is etiologically associated with various kinds of malignant and benign diseases, accounting for 265,000 cancer incident cases and 164,000 cancer deaths in 2017. EBV prophylactic vaccine development has been gp350 centered for several decades. However, clinical studies show that gp350-centered vaccines fail to prevent EBV infection. Advances in the EBV infection mechanisms shed light on gB and gHgL, the two key components of the infection apparatus. In this study, for the first time, we utilized recombinant vesicular stomatitis virus (VSV) to display EBV gB (VSV-ΔG-gB/gB-G) or gHgL (VSV-ΔG-gHgL). In vitro studies confirmed successful virion production and glycoprotein presentation on the virion surface. In mouse models, VSV-ΔG-gB/gB-G or VSV-ΔG-gHgL elicited potent humoral responses. Neutralizing antibodies elicited by VSV-ΔG-gB/gB-G were prone to prevent B cell infection, while those elicited by VSV-ΔG-gHgL were prone to prevent epithelial cell infection. Combinatorial vaccination yields an additive effect. The ratio of endpoint neutralizing antibody titers to the endpoint total IgG titers immunized with VSV-ΔG-gHgL was approximately 1. The ratio of IgG1/IgG2a after VSV-ΔG-gB/gB-G immunization was approximately 1 in a dose-dependent, adjuvant-independent manner. Taken together, VSV-based EBV vaccines can elicit a high ratio of epithelial and B lymphocyte neutralizing antibodies, implying their unique potential as EBV prophylactic vaccine candidates.

IMPORTANCE Epstein-Barr virus (EBV), one of the most common human viruses and the first identified human oncogenic virus, accounted for 265,000 cancer incident cases and 164,000 cancer deaths in 2017 as well as millions of nonmalignant disease cases. So far, no prophylactic vaccine is available to prevent EBV infection. In this study, for the first time, we reported the VSV-based EBV vaccines presenting two key components of the EBV infection apparatus, gB and gHgL. We confirmed potent antigen-specific antibody generation; these antibodies prevented EBV from infecting epithelial cells and B cells, and the IgG1/IgG2a ratio indicated balanced humoral-cellular responses. Taken together, we suggest VSV-based EBV vaccines are potent prophylactic candidates for clinical studies and help eradicate numerous EBV-associated malignant and benign diseases.

Dose-Dependent Outcome of EBV Infection of Humanized Mice Based on Green Raji Unit (GRU) Doses

Humanized mouse models are used as comprehensive small-animal models of EBV infection. Previously, infectious doses of EBV used in vivo have been determined mainly on the basis of TD₅₀ (50% transforming dose), which is a time-consuming process. Here, we determined infectious doses of Akata-EBV-GFP using green Raji units (GRUs), and characterized dose-dependent effects in humanized mice. We defined two outcomes in vivo, including an infection model and a lymphoma model, following inoculation with low or high doses of Akata-EBV-GFP, respectively. Inoculation with a low dose induced primary B cells to become lymphoblastoid cell lines in vitro, and caused latent infection in humanized mice. In contrast, a high dose of Akata-EBV-GFP resulted in primary B cells death in vitro, and fatal B cell lymphomas in vivo. Following infection with high doses, the frequency of CD19⁺ B cells decreased, whereas the percentage of CD8⁺ T cells increased in peripheral blood and the spleen. At such doses, a small part of activated CD8⁺ T cells was EBV-specific CD8⁺ T cells. Thus, GRUs quantitation of Akata-EBV-GFP is an effective way to quantify infectious doses to study pathologies, immune response, and to assess (in vivo) the neutralizing activity of antibodies raised by immunization against EBV.