A potent and protective human neutralizing antibody targeting a novel vulnerable site of Epstein-Barr virus

Multivalent MVA-vectored vaccine elicits EBV neutralizing antibodies in rhesus macaques that reduce EBV infection in humanized mice

Introduction

Epstein-Barr virus (EBV) is an oncogenic human herpesvirus associated with ~350,000 cases of lymphoid and epithelial malignancies every year, and is etiologically linked to infectious mononucleosis and multiple sclerosis. Despite four decades of research, no EBV vaccine candidate has yet reached licensure. Most previous vaccine attempts focused on a single viral entry glycoprotein, gp350, but recent data from clinical and pre-clinical studies, and the elucidation of viral entry mechanisms, support the inclusion of multiple entry glycoproteins in EBV vaccine design.

Methods

Here we generated a modified vaccinia Ankara (MVA)-vectored EBV vaccine, MVA-EBV5-2, that targets five EBV entry glycoproteins, gp350, gB, and the gp42gHgL complex. We characterized the genetic and translational stability of the vaccine, followed by immunogenicity assessment in BALB/c mice and rhesus lymphocryptovirus-negative rhesus macaques as compared to a gp350-based MVA vaccine. Finally, we assessed the efficacy of MVA-EBV5-2-immune rhesus serum at preventing EBV infection in human CD34+ hematopoietic stem cell-reconstituted NSG mice, under two EBV challenge doses.

Results

The MVA-EBV5-2 vaccine was genetically and translationally stable over 10 viral passages as shown by genetic and protein expression analysis, and when administered to female and male BALB/c mice, elicited serum EBV-specific IgG of both IgG1 and IgG2a subtypes with neutralizing activity in vitro. In Raji B cells, this neutralizing activity outperformed that of serum from mice immunized with a monovalent MVA-vectored gp350 vaccine. Similarly, MVA-EBV5-2 elicited EBV-specific IgG in rhesus macaques that were detected in both serum and saliva of immunized animals, with serum antibodies demonstrating neutralizing activity in vitro that outperformed serum from MVA-gp350-immunized macaques. Finally, pre-treatment with serum from MVA-EBV5-2-immunized macaques resulted in fewer EBV-infected mice in the two challenge experiments than pretreatment with serum from pre-immune macaques or macaques immunized with the monovalent gp350-based vaccine.

Discussion

These results support the inclusion of multiple entry glycoproteins in EBV vaccine design and position our vaccine as a strong candidate for clinical translation.

Single-cell and spatial transcriptome analyses reveal tertiary lymphoid structures linked to tumour progression and immunotherapy response in nasopharyngeal carcinoma

Tertiary lymphoid structures are immune cell aggregates linked with cancer outcomes, but their interactions with tumour cell aggregates are unclear. Using nasopharyngeal carcinoma as a model, here we analyse single-cell transcriptomes of 343,829 cells from 77 biopsy and blood samples and spatially-resolved transcriptomes of 31,316 spots from 15 tumours to decipher their components and interactions with tumour cell aggregates. We identify essential cell populations in tertiary lymphoid structure, including CXCL13+ cancer-associated fibroblasts, stem-like CXCL13+CD8+ T cells, and B and T follicular helper cells. Our study shows that germinal centre reaction matures plasma cells. These plasma cells intersperse with tumour cell aggregates, promoting apoptosis of EBV-related malignant cells and enhancing immunotherapy response. CXCL13+ cancer-associated fibroblasts promote B cell adhesion and antibody production, activating CXCL13+CD8+ T cells that become exhausted in tumour cell aggregates. Tertiary lymphoid structure-related cell signatures correlate with prognosis and PD-1 blockade response, offering insights for therapeutic strategies in cancers.

Association Between Antibodies That Bind Epstein-Barr Virus (EBV) gp350 and gH/gL and Shedding of EBV in Saliva From Nasopharyngeal Carcinoma Multiplex Family Members in Taiwan

Elevated levels of Epstein-Barr virus (EBV) gp350 and gH/gL antibodies have been associated with a lower risk of developing nasopharyngeal carcinoma (NPC), although the evidence remains inconclusive and unexplained. We conducted a longitudinal study within a high-risk Taiwanese cohort, analyzing total immunoglobulin against EBV-gp350 and -gH/gL in blood and EBV DNA shedding in saliva. Contrary to our hypothesis-that elevated levels of antibodies previously shown to be associated with a lower NPC risk should result in a decrease in EBV shedding in saliva-higher anti-gp350 antibodies at baseline were significantly associated with detectable EBV DNA in saliva at follow-up (odds ratio [OR], 1.99 [95% confidence interval {CI}, 1.03-3.97]; P = .04). Higher anti-EBV-gH/gL antibodies at baseline were not significantly associated with risk of detectable EBV DNA at follow-up (OR, 0.69 [95% CI, .35-1.32]; P = .26). These findings underscore the complexity of virus-host interactions and emphasize the need for further investigations into their role in EBV-associated diseases.

GB and gH/gL fusion machinery: a promising target for vaccines to prevent Epstein-Barr virus infection

Epstein‒Barr virus (EBV) is a double-stranded DNA virus belonging to the family Orthoherpesviridae that is associated with the development of various tumors, such as lymphoma, nasopharyngeal carcinoma, and gastric cancer. There are no uniformly effective treatments for human EBV infection, and vaccines and immunotherapies are currently the main research directions. The glycoproteins gB and gH/gL are surface glycoproteins that are common to all herpesviruses, with subtle differences in structure and function between different viruses. The core membrane fusion machinery constituted by EBV gB and gH/gL is an important target of neutralizing antibodies in epithelial EBV infection due to its essential role in the fusion of viral and target cell membranes. In this article, we review the main modes of EBV infection, the structure and function of the core fusion machinery gB and gH/gL, and the development of neutralizing antibodies and prophylactic vaccines based on this target.

A metabolic dependency of EBV can be targeted to hinder B cell transformation

After infection of B cells, Epstein-Barr virus (EBV) engages host pathways that mediate cell proliferation and transformation, contributing to the propensity of the virus to drive immune dysregulation and lymphomagenesis. We found that the EBV protein EBNA2 initiates nicotinamide adenine dinucleotide (NAD) de novo biosynthesis by driving expression of the metabolic enzyme indoleamine 2,3-dioxygenase 1 (IDO1) in infected B cells. Virus-enforced NAD production sustained mitochondrial complex I activity, to match adenosine triphosphate (ATP) production with bioenergetic requirements of proliferation and transformation. In transplant patients, IDO1 expression in EBV-infected B cells, and a serum signature of increased IDO1 activity, preceded development of lymphoma. In humanized mice infected with EBV, IDO1 inhibition reduced both viremia and lymphomagenesis. Virus-orchestrated NAD biosynthesis is therefore a druggable metabolic vulnerability of EBV-driven B cell transformation, opening therapeutic possibilities for EBV-related diseases.

A gH/gL-encoding replicon vaccine elicits neutralizing antibodies that protect humanized mice against EBV challenge

Epstein-Barr virus (EBV) is associated with several malignancies, neurodegenerative disorders and is the causative agent of infectious mononucleosis. A vaccine that prevents EBV-driven morbidity and mortality remains an unmet need. EBV is orally transmitted, infecting both B cells and epithelial cells. Several virally encoded proteins are involved in entry. The gH/gL glycoprotein complex is essential for infectivity irrespective of cell type, while gp42 is essential for infection of B cells. gp350 promotes viral attachment by binding to CD21 or CD35 and is the most abundant glycoprotein on the virion. gH/gL, gp42 and gp350, are known targets of neutralizing antibodies and therefore relevant immunogens for vaccine development. Here, we developed and optimized the delivery of several alphavirus-derived replicon RNA (repRNA) vaccine candidates encoding gH/gL, gH/gL/gp42 or gp350 delivered by a cationic nanocarrier termed LION™. The lead candidate, encoding full-length gH/gL, elicited high titers of neutralizing antibodies that persisted for at least 8 months and a vaccine-specific CD8+ T cell response. Transfer of vaccine-elicited IgG protected humanized mice from EBV-driven tumor formation and death following high-dose viral challenge. These data demonstrate that LION/repRNA-gH/gL is an ideal candidate vaccine for preventing EBV infection and/or related malignancies in humans.

Vaccination with nanoparticles displaying gH/gL from Epstein-Barr virus elicits limited cross-protection against rhesus lymphocryptovirus

Epstein-Barr virus (EBV) is associated with infectious mononucleosis, cancer, and multiple sclerosis. A vaccine that prevents infection and/or EBV-associated morbidity is an unmet need. The viral gH/gL glycoprotein complex is essential for infectivity, making it an attractive vaccine target. Here, we evaluate the immunogenicity of a gH/gL nanoparticle vaccine adjuvanted with the Sigma Adjuvant System (SAS) or a saponin/monophosphoryl lipid A nanoparticle (SMNP) in rhesus macaques. Formulation with SMNP elicits higher titers of neutralizing antibodies and more vaccine-specific CD4+ T cells. All but one animal in the SMNP group were infected after oral challenge with the EBV ortholog rhesus lymphocryptovirus (rhLCV). Their immune plasma had a 10- to 100-fold lower reactivity against rhLCV gH/gL compared to EBV gH/gL. Anti-EBV neutralizing monoclonal antibodies showed reduced binding to rhLCV gH/gL, demonstrating that EBV gH/gL neutralizing epitopes are poorly conserved on rhLCV gH/gL. Prevention of rhLCV infection despite antigenic disparity supports clinical development of gH/gL nanoparticle vaccines against EBV.

Potent human monoclonal antibodies targeting Epstein-Barr virus gp42 reveal vulnerable sites for virus infection

Epstein-Barr virus (EBV) is linked to various malignancies and autoimmune diseases, posing a significant global health challenge due to the lack of specific treatments or vaccines. Despite its crucial role in EBV infection in B cells, the mechanisms of the glycoprotein gp42 remain elusive. In this study, we construct an antibody phage library from 100 EBV-positive individuals, leading to the identification of two human monoclonal antibodies, 2B7 and 2C1. These antibodies effectively neutralize EBV infection in vitro and in vivo while preserving gp42's interaction with the human leukocyte antigen class II (HLA-II) receptor. Structural analysis unveils their distinct binding epitopes on gp42, different from the HLA-II binding site. Furthermore, both 2B7 and 2C1 demonstrate potent neutralization of EBV infection in HLA-II-positive epithelial cells, expanding our understanding of gp42's role. Overall, this study introduces two human anti-gp42 antibodies with potential implications for developing EBV vaccines targeting gp42 epitopes, addressing a critical gap in EBV research.

Epstein-Barr virus gp42 antibodies reveal sites of vulnerability for receptor binding and fusion to B cells

Epstein-Barr virus (EBV) causes infectious mononucleosis and is associated with B cell lymphomas. EBV glycoprotein 42 (gp42) binds HLA class II and activates membrane fusion with B cells. We isolated gp42-specific monoclonal antibodies (mAbs), A10 and 4C12, which use distinct mechanisms to neutralize virus infection. mAb A10 was more potent than the only known neutralizing gp42 mAb, F-2-1, in neutralizing EBV infection and blocking binding to HLA class II. mAb 4C12 was similar to mAb A10 in inhibiting glycoprotein-mediated B cell fusion but did not block receptor binding, and it was less effective in neutralizing infection. Crystallographic structures of gH/gL/gp42/A10 and gp42/4C12 complexes revealed two distinct sites of vulnerability on gp42 for receptor binding and B cell fusion. Passive transfer of mAb A10 into humanized mice conferred nearly 100% protection from viremia and EBV lymphomas after EBV challenge. These findings identify vulnerable sites on EBV that may facilitate therapeutics and vaccines.

EPHA2 Receptor as a Possible Therapeutic Target in Viral Infections

BACKGROUND

The receptor tyrosine kinase EphA2 plays a role in many diseases, like cancer, cataracts, and osteoporosis. Interestingly, it has also been linked to viral infections.

OBJECTIVE

Herein, current literature has been reviewed to clarify EphA2 functions in viral infections and explore its potential role as a target in antiviral drug discovery strategies.

METHODS

Research and review articles along with preprints connecting EphA2 to different viruses have been searched through PubMed and the web. Structures of complexes between EphA2 domains and viral proteins have been retrieved from the PDB database.

RESULTS

EphA2 assumes a key role in Kaposi's sarcoma-associated herpesvirus (KSHV) and Epstein Barr virus (EBV) infections by directly binding, through its ligand binding domain, viral glycoproteins. For human cytomegalovirus (HCMV), the role of EphA2 in maintaining virus latency state, through cooperation with specific viral proteins, has also been speculated. In certain cells, with high EphA2 expression levels, following ligand stimulation, receptor activation might contribute to severe symptoms accompanying a few viral infections, including lung injuries often related to severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2).

CONCLUSION

Since EphA2 works as a host receptor for certain viruses, it might be worth more deeply investigating known compounds targeting its extracellular ligand binding domain as antiviral therapeutics. Due to EphA2's function in inflammation, its possible correlation with SARS-CoV-2 cannot be excluded, but more experimental studies are needed in this case to undoubtedly attribute the role of this receptor in viral infections.

Antibody and Cell-Based Therapies against Virus-Induced Cancers in the Context of HIV/AIDS

Infectious agents, notably viruses, can cause or increase the risk of cancer occurrences. These agents often disrupt normal cellular functions, promote uncontrolled proliferation and growth, and trigger chronic inflammation, leading to cancer. Approximately 20% of all cancer cases in humans are associated with an infectious pathogen. The International Agency for Research on Cancer (IARC) recognizes seven viruses as direct oncogenic agents, including Epstein-Barr Virus (EBV), Kaposi's Sarcoma-associated herpesvirus (KSHV), human T-cell leukemia virus type-1 (HTLV-1), human papilloma virus (HPV), hepatitis C virus (HCV), hepatitis B virus (HBV), and human immunodeficiency virus type 1 (HIV-1). Most viruses linked to increased cancer risk are typically transmitted through contact with contaminated body fluids and high-risk behaviors. The risk of infection can be reduced through vaccinations and routine testing, as well as recognizing and addressing risky behaviors and staying informed about public health concerns. Numerous strategies are currently in pre-clinical phases or undergoing clinical trials for targeting cancers driven by viral infections. Herein, we provide an overview of risk factors associated with increased cancer incidence in people living with HIV (PLWH) as well as other chronic viral infections, and contributing factors such as aging, toxicity from ART, coinfections, and comorbidities. Furthermore, we highlight both antibody- and cell-based strategies directed against virus-induced cancers while also emphasizing approaches aimed at discovering cures or achieving complete remission for affected individuals.

Non-overlapping epitopes on the gHgL-gp42 complex for the rational design of a triple-antibody cocktail against EBV infection

Epstein-Barr virus (EBV) is closely associated with cancer, multiple sclerosis, and post-acute coronavirus disease 2019 (COVID-19) sequelae. There are currently no approved therapeutics or vaccines against EBV. It is noteworthy that combining multiple EBV glycoproteins can elicit potent neutralizing antibodies (nAbs) against viral infection, suggesting possible synergistic effects. Here, we characterize three nAbs (anti-gp42 5E3, anti-gHgL 6H2, and anti-gHgL 10E4) targeting different glycoproteins of the gHgL-gp42 complex. Two antibody cocktails synergistically neutralize infection in B cells (5E3+6H2+10E4) and epithelial cells (6H2+10E4) in vitro. Moreover, 5E3 alone and the 5E3+6H2+10E4 cocktail confer potent in vivo protection against lethal EBV challenge in humanized mice. The cryo-EM structure of a heptatomic gHgL-gp42 immune complex reveals non-overlapping epitopes of 5E3, 6H2, and 10E4 on the gHgL-gp42 complex. Structural and functional analyses highlight different neutralization mechanisms for each of the three nAbs. In summary, our results provide insight for the rational design of therapeutics or vaccines against EBV infection.

A gB nanoparticle vaccine elicits a protective neutralizing antibody response against EBV

Epstein-Barr virus (EBV) is a global public health concern, as it is known to cause multiple diseases while also being etiologically associated with a wide range of epithelial and lymphoid malignancies. Currently, there is no available prophylactic vaccine against EBV. gB is the EBV fusion protein that mediates viral membrane fusion and participates in host recognition, making it critical for EBV infection in both B cells and epithelial cells. Here, we present a gB nanoparticle, gB-I53-50 NP, that displays multiple copies of gB. Compared with the gB trimer, gB-I53-50 NP shows improved structural integrity and stability, as well as enhanced immunogenicity in mice and non-human primate (NHP) preclinical models. Immunization and passive transfer demonstrate a robust and durable protective antibody response that protects humanized mice against lethal EBV challenge. This vaccine candidate demonstrates significant potential in preventing EBV infection, providing a possible platform for developing prophylactic vaccines for EBV.

Anti-EBV antibodies: Roles in diagnosis, pathogenesis, and antiviral therapy

Epstein-Barr virus (EBV) infection is prevalent in global population and associated with multiple malignancies and autoimmune diseases. During the infection, EBV-harbored or infected cell-expressing antigen could elicit a variety of antibodies with significant role in viral host response and pathogenesis. These antibodies have been extensively evaluated and found to be valuable in predicting disease diagnosis and prognosis, exploring disease mechanisms, and developing antiviral agents. In this review, we discuss the versatile roles of EBV antibodies as important biomarkers for EBV-related diseases, potential driving factors of autoimmunity, and promising therapeutic agents for viral infection and pathogenesis.

Immunotherapy of Epstein-Barr virus (EBV) infection and EBV-associated hematological diseases with gp350/CD89-targeted bispecific antibody

Acute and persistent infection of Epstein-Barr virus (EBV) is associated with several life-threatening hematological disorders, including lymphoproliferative disorders (LPD), hemophagocytic lymphohistiocytosis (HLH), and chronic active Epstein-Barr virus infection (CAEBV). Currently, there are no efficacious virus-targeted therapies for EBV-driven hematological diseases. To explore the potential of phagocytosis-based immunotherapy, we created a bispecific antibody by targeting the viral envelope protein gp350 with a novel EBV-neutralizing antibody (named R1) that was paired with a monoclonal antibody against CD89 for redirecting macrophages and neutrophils. In vitro study showed that the bispecific antibody enabled efficient phagocytosis of EBV and killing of gp350 + lymphoma cells in the presence of PBMC. In vivo studies in NSG mice inoculated with EBV showed that bispecific antibody dramatically reduced the viral load in blood, solid organs and tissues. Treatment of mice implanted with EBV-harboring Raji lymphoma cells efficiently prevented tumor formation and massive metastasis to solid organs. Treatment of mice implanted with whole blood from EBV-HLH patients was effective in reducing viral levels in blood and solid organ. The gp350/CD89 bispecific antibody was highly effective in clearing EBV and immunotherapy of EBV-driven hematological diseases such as LPD and EBV-HLH.

Assessing the Efficacy of VLP-Based Vaccine against Epstein-Barr Virus Using a Rabbit Model

Epstein–Barr virus (EBV) is etiologically associated with a number of malignant and non-malignant conditions. Thus, a prophylactic vaccine against this virus could help to reduce the burden of many EBV-associated diseases. Previously, we reported that an EBV virus-like particle (VLP) vaccine was highly immunogenic and produced a strong humoral response in mice. However, since EBV does not infect mice, the efficacy of the VLP in preventing EBV infection could not be addressed. Here we examined, for the first time, the efficacy of the EBV-VLP vaccine using a novel rabbit model of EBV infection. Animals vaccinated with two doses of VLP elicited higher antibody responses to total EBV antigens compared to animals receiving one dose. Vaccinated animals also elicited both IgM and IgG to EBV-specific antigens, VCA and EBNA1. Analysis of peripheral blood and spleen for EBV copy number indicated that the viral load in both of these compartments was lower in animals receiving a 2-dose vaccine. However, the VLP vaccine was ineffective in preventing EBV infection. With several other EBV vaccine candidates currently at various stages of development and testing, we believe that the rabbit model of EBV infection could be a great platform for evaluating potential candidates.

A high-throughput neutralizing assay for antibodies and sera evaluation against Epstein-Barr virus

BACKGROUND

Epstein-Barr virus (EBV) is a wide-spread human herpesvirus that is highly associated with infectious mononucleosis and several malignancies. Evaluation of EBV neutralizing antibody titers is important for serological studies, vaccine development and monoclonal antibody screening. The traditional method based on antibody inhibition of EBV transformation of B cells is very time-consuming. A more practical flow cytometry-based (FCM) approach to evaluate neutralizing titers is not amenable to achieving high-throughput evaluation of large-scale samples. A high-throughput approach is urgently needed.

RESULTS

Here, we present a rapid and high-throughput method based on high content imaging system (HCIS) analysis. EBV titers determined by the HCIS-based assay were similar to those obtained by the FCM-based assay. Neutralizing titers of sera and monoclonal antibodies measured by the HCIS-based assay strongly correlated with titers measured by the FCM-based assay. HCIS assays showed a strong correlation between B cell infection neutralizing titers and the anti-gp350 IgG titers in healthy EBV carriers and monkey sera. Finally, anti-gHgL IgG titers from sera of healthy EBV carriers significantly correlated with epithelial cell infection neutralizing titers.

CONCLUSIONS

This HCIS-based assay is a high-throughput assay to determine viral titers and evaluate neutralizing potentials of sera and monoclonal antibodies. This HCIS-based assay will aid the development of vaccines and therapeutic monoclonal antibody against EBV.

Epstein-Barr virus gH/gL has multiple sites of vulnerability for virus neutralization and fusion inhibition

Epstein-Barr virus (EBV) is nearly ubiquitous in adults. EBV causes infectious mononucleosis and is associated with B cell lymphomas, epithelial cell malignancies, and multiple sclerosis. The EBV gH/gL glycoprotein complex facilitates fusion of virus membrane with host cells and is a target of neutralizing antibodies. Here, 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.

Protective anti-gB neutralizing antibodies targeting two vulnerable sites for EBV-cell membrane fusion

Epstein-Barr virus (EBV) accounts for 200,000 new epithelial and B cell malignancy cases and 140,000 deaths annually. Glycoprotein B (gB) is the sole fusogen that is highly conserved and essential for all herpesvirus entry into target cells and thus, is attracting attention to identify potent antibodies to neutralize viral infection. Here, we discovered two anti-EBV gB neutralizing antibodies, 3A3 and 3A5, that effectively neutralized EBV infection of both B and epithelial cells. They also potently protected against EBV-induced lymphoproliferative disorders in humanized mice. Importantly, the 3A3 and 3A5 epitopes identified here represent the neutralizing antigenic sites to block EBV infection and membrane fusion. They are major targets of protective gB-specific neutralizing antibodies elicited by natural EBV infection in humans.

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.

Immunization with a self-assembling nanoparticle vaccine displaying EBV gH/gL protects humanized mice against lethal viral challenge

Epstein-Barr virus (EBV) is a cancer-associated pathogen responsible for 165,000 deaths annually. EBV is also the etiological agent of infectious mononucleosis and is linked to multiple sclerosis and rheumatoid arthritis. Thus, an EBV vaccine would have a significant global health impact. EBV is orally transmitted and has tropism for epithelial and B cells. Therefore, a vaccine would need to prevent infection of both in the oral cavity. Passive transfer of monoclonal antibodies against the gH/gL glycoprotein complex prevent experimental EBV infection in humanized mice and rhesus macaques, suggesting that gH/gL is an attractive vaccine candidate. Here, we evaluate the immunogenicity of several gH/gL nanoparticle vaccines. All display superior immunogenicity relative to monomeric gH/gL. A nanoparticle displaying 60 copies of gH/gL elicits antibodies that protect against lethal EBV challenge in humanized mice, whereas antibodies elicited by monomeric gH/gL do not. These data motivate further development of gH/gL nanoparticle vaccines for EBV.

Glycoprotein B Antibodies Completely Neutralize EBV Infection of B Cells

The Epstein-Barr virus (EBV) is the first reported oncogenic herpesvirus that establishes persistent infection in B lymphocytes in 95% of adults worldwide. Glycoprotein B (gB) plays a predominant role in the fusion of the viral envelope with the host cell membrane. Hence, it is of great significance to isolate gB-specific fusion-inhibiting neutralizing antibodies (NAbs). AMMO5 is the only gB NAb but fails to antagonize B-cell infection. It is essential to isolate potent NAbs that can completely block EBV infection of B cells. Using hybridoma technology and neutralization assay, we isolate two gB NAbs 8A9 and 8C12 that are capable of completely neutralizing B-cell infection in vitro. In addition, 8A9 shows cross-reactivity with rhesus lymphocryptovirus (rhLCV) gB. Competitive binding experiments demonstrate that 8A9 and 8C12 recognize novel epitopes that are different from the AMMO5 epitope. The epitopes of 8A9 and 8C12 are mapped to gB D-II, and the AMMO5 epitope is located precisely at gB aa 410-419. We find that 8A9 and 8C12 significantly inhibit gB-derived membrane fusion using a virus-free fusion assay. In summary, this study identifies two gB-specific NAbs that potently block EBV infection of B cells. Our work highlights the importance of gB D-II as a predominant neutralizing epitope, and aids in the rational design of therapeutics or vaccines based on gB.

A bivalent Epstein-Barr virus vaccine induces neutralizing antibodies that block infection and confer immunity in humanized mice

Epstein-Barr virus (EBV) is the major cause of infectious mononucleosis and is associated with several human cancers and, more recently, multiple sclerosis. Despite its prevalence and health impact, there are currently no vaccines or treatments. Four viral glycoproteins (gp), gp350 and gH/gL/gp42, mediate entry into the major sites of viral replication, B cells, and epithelial cells. Here, we designed a nanoparticle vaccine displaying these proteins and showed that it elicits potent neutralizing antibodies that protect against infection in vivo. We designed single-chain gH/gL and gH/gL/gp42 proteins 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 proteins, and the protein spikes were observed by electron microscopy. Single-chain gH/gL or gH/gL/gp42 nanoparticle vaccines were constructed to ensure product homogeneity needed for clinical development. 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, gp350D₁₂₃, no immune competition was observed. To confirm its efficacy in vivo, humanized mice were challenged with EBV after passive transfer of IgG from mice vaccinated with control, gH/gL/gp42+gp350D₁₂₃, or gH/gL+gp350D₁₂₃ 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.

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.

Well Put Together-A Guide to Accessorizing with the Herpesvirus gH/gL Complexes

Herpesviruses are enveloped, double-stranded DNA viruses that infect a variety of hosts across the animal kingdom. Nine of these establish lifelong infections in humans, for which there are no cures and few vaccine or treatment options. Like all enveloped viruses, herpesviruses enter cells by fusing their lipid envelopes with a host cell membrane. Uniquely, herpesviruses distribute the functions of receptor engagement and membrane fusion across a diverse cast of glycoproteins. Two glycoprotein complexes are conserved throughout the three herpesvirus subfamilies: the trimeric gB that functions as a membrane fusogen and the heterodimeric gH/gL, the role of which is less clearly defined. Here, we highlight the conserved and divergent functions of gH/gL across the three subfamilies of human herpesviruses by comparing its interactions with a broad range of accessory viral proteins, host cell receptors, and neutralizing or inhibitory antibodies. We propose that the intrinsic structural plasticity of gH/gL enables it to function as a signal integration machine that can accept diverse regulatory inputs and convert them into a "trigger" signal that activates the fusogenic ability of gB.