An Antibody Targeting the Fusion Machinery Neutralizes Dual-Tropic Infection and Defines a Site of Vulnerability on Epstein-Barr Virus

Epstein-Barr virus-associated post-transplant lymphoproliferative disorders in pediatric transplantation: A prospective multicenter study in the United States

BACKGROUND

Epstein-Barr virus (EBV)-associated post-transplant lymphoproliferative disorders (PTLD) is the most common malignancy in children after transplant; however, difficulties for early detection may worsen the prognosis.

METHODS

The prospective, multicenter, study enrolled 944 children (≤21 years of age). Of these, 872 received liver, heart, kidney, intestinal, or multivisceral transplants in seven US centers between 2014 and 2019 (NCT02182986). In total, 34 pediatric EBV+ PTLD (3.9%) were identified by biopsy. Variables included sex, age, race, ethnicity, transplanted organ, EBV viral load, pre-transplant EBV serology, immunosuppression, response to chemotherapy and rituximab, and histopathological diagnosis.

RESULTS

The uni-/multivariable competing risk analyses revealed the combination of EBV-seropositive donor and EBV-naïve recipient (D+R-) was a significant risk factor for PTLD development (sub-hazard ratio: 2.79 [1.34-5.78], p = .006) and EBV DNAemia (2.65 [1.72-4.09], p < .001). Patients with D+R- were significantly more associated with monomorphic/polymorphic PTLD than those with the other combinations (p = .02). Patients with monomorphic/polymorphic PTLD (n = 21) had significantly more EBV DNAemia than non-PTLD patients (p < .001) and an earlier clinical presentation of PTLD than patients with hyperplasias (p < .001), within 6-month post-transplant. Among non-liver transplant recipients, monomorphic/polymorphic PTLD were significantly more frequent than hyperplasias in patients ≥5 years of age at transplant (p = .01).

CONCLUSIONS

D+R- is a risk factor for PTLD and EBV DNAemia and associated with the incidence of monomorphic/polymorphic PTLD. Intensive follow-up of EBV viral load within 6-month post-transplant, especially for patients with D+R- and/or non-liver transplant recipients ≥5 years of age at transplant, may help detect monomorphic/polymorphic PTLD early in pediatric transplant.

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

Following 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 NAD de novo biosynthesis by driving expression of the metabolic enzyme IDO1 in infected B cells. Virus-enforced NAD production sustained mitochondrial complex I activity, to match 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, thus, a druggable metabolic vulnerability of EBV-driven B cell transformation-opening therapeutic possibilities for EBV-related diseases.

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.

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.

Deciphering the Role of Epstein-Barr Virus Latent Membrane Protein 1 in Immune Modulation: A Multifaced Signalling Perspective

The disruption of antiviral sensors and the evasion of immune defences by various tactics are hallmarks of EBV infection. One of the EBV latent gene products, LMP1, was shown to induce the activation of signalling pathways, such as NF-κB, MAPK (JNK, ERK1/2, p38), JAK/STAT and PI3K/Akt, via three subdomains of its C-terminal domain, regulating the expression of several cytokines responsible for modulation of the immune response and therefore promoting viral persistence. The aim of this review is to summarise the current knowledge on the EBV-mediated induction of immunomodulatory molecules by the activation of signal transduction pathways with a particular focus on LMP1-mediated mechanisms. A more detailed understanding of the cytokine biology molecular landscape in EBV infections could contribute to the more complete understanding of diseases associated with this virus.

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.

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.

Neutralizing antibodies against EBV gp42 show potent in vivo protection and define novel epitopes

Epstein-Barr virus (EBV) is the first reported human oncogenic virus and infects more than 95% of the human population worldwide. EBV latent infection in B lymphocytes is essential for viral persistence. Glycoprotein gp42 is an indispensable member of the triggering complex for EBV entry into B cells. The C-type lectin domain (CTLD) of gp42 plays a key role in receptor binding and is the major target of neutralizing antibodies. Here, we isolated two rabbit antibodies, 1A7 and 6G7, targeting gp42 CTLD with potent neutralizing activity against B cell infection. Antibody 6G7 efficiently protects humanized mice from lethal EBV challenge and EBV-induced lymphoma. Neutralizing epitopes targeted by antibodies 1A7 and 6G7 are distinct and novel. Antibody 6G7 blocks gp42 binding to B cell surface and both 1A7 and 6G7 inhibit membrane fusion with B cells. Furthermore, 1A7- and 6G7-like antibodies in immunized sera are major contributors to B cell neutralization. This study demonstrates that anti-gp42 neutralizing antibodies are effective in inhibiting EBV infection and sheds light on the design of gp42-based vaccines and therapeutics.

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.

Epstein-Barr virus infectious particles initiate B cell transformation and modulate cytokine response

IMPORTANCE

The Epstein-Barr virus efficiently infects and transforms B lymphocytes. During this process, infectious viral particles transport the viral genome to the nucleus of target cells. We show here that these complex viral structures serve additional crucial roles by activating transcription of the transforming genes encoded by the virus. We show that components of the infectious particle sequentially activate proinflammatory B lymphocyte signaling pathways that, in turn, activate viral gene expression but also cause cytokine release. However, virus infection activates expression of ZFP36L1, an RNA-binding stress protein that limits the length and the intensity of the cytokine response. Thus, the infectious particles can activate viral gene expression and initiate cellular transformation at the price of a limited immune response.

Raman Multi-Omic Snapshot and Statistical Validation of Structural Differences between Herpes Simplex Type I and Epstein-Barr Viruses

Raman spectroscopy was applied to study the structural differences between herpes simplex virus Type I (HSV-1) and Epstein-Barr virus (EBV). Raman spectra were first collected with statistical validity on clusters of the respective virions and analyzed according to principal component analysis (PCA). Then, average spectra were computed and a machine-learning approach applied to deconvolute them into sub-band components in order to perform comparative analyses. The Raman results revealed marked structural differences between the two viral strains, which could mainly be traced back to the massive presence of carbohydrates in the glycoproteins of EBV virions. Clear differences could also be recorded for selected tyrosine and tryptophan Raman bands sensitive to pH at the virion/environment interface. According to the observed spectral differences, Raman signatures of known biomolecules were interpreted to link structural differences with the viral functions of the two strains. The present study confirms the unique ability of Raman spectroscopy for answering structural questions at the molecular level in virology and, despite the structural complexity of viral structures, its capacity to readily and reliably differentiate between different virus types and strains.

Epstein‒Barr virus-associated cellular immunotherapy

Epstein‒Barr virus (EBV) is a human herpes virus that is saliva-transmissible and universally asymptomatic. It has been confirmed that more than 90% of the population is latently infected with EBV for life. EBV can cause a variety of related cancers, such as nasopharyngeal carcinoma, diffuse large B-cell lymphoma, and Burkitt lymphoma. Currently, many clinical studies have demonstrated that EBV-specific cytotoxic T lymphocytes and other cell therapies can be safely and effectively transfused to prevent and treat some diseases caused by EBV. This review will mainly focus on discussing EBV-specific cytotoxic T lymphocytes and will touch on therapeutic EBV vaccines and chimeric antigen receptor T-cell therapy briefly.

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.

CD4 binding site immunogens elicit heterologous anti-HIV-1 neutralizing antibodies in transgenic and wild-type animals

Passive transfer of broadly neutralizing anti-HIV-1 antibodies (bNAbs) protects against infection, and therefore, eliciting bNAbs by vaccination is a major goal of HIV-1 vaccine efforts. bNAbs that target the CD4 binding site (CD4bs) on HIV-1 Env are among the most broadly active, but to date, responses elicited against this epitope in vaccinated animals have lacked potency and breadth. We hypothesized that CD4bs bNAbs resembling the antibody IOMA might be easier to elicit than other CD4bs antibodies that exhibit higher somatic mutation rates, a difficult-to-achieve mechanism to accommodate Env's N276gp120 N-glycan, and rare five-residue light chain complementarity-determining region 3. As an initial test of this idea, we developed IOMA germline-targeting Env immunogens and evaluated a sequential immunization regimen in transgenic mice expressing germline-reverted IOMA. These mice developed CD4bs epitope-specific responses with heterologous neutralization, and cloned antibodies overcame neutralization roadblocks, including accommodating the N276gp120 glycan, with some neutralizing selected HIV-1 strains more potently than IOMA. The immunization regimen also elicited CD4bs-specific responses in mice containing polyclonal antibody repertoires as well as rabbits and rhesus macaques. Thus, germline targeting of IOMA-class antibody precursors represents a potential vaccine strategy to induce CD4bs bNAbs.

Urgency and necessity of Epstein-Barr virus prophylactic vaccines

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.

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.

Adjuvants influence the maturation of VRC01-like antibodies during immunization

Once naive B cells expressing germline VRC01-class B cell receptors become activated by germline-targeting immunogens, they enter germinal centers and undergo affinity maturation. Booster immunizations with heterologous Envs are required for the full maturation of VRC01-class antibodies. Here, we examined whether and how three adjuvants, Poly(I:C), GLA-LSQ, or Rehydragel, that activate different pathways of the innate immune system, influence the rate and type of somatic mutations accumulated by VRC01-class BCRs that become activated by the germline-targeting 426c.Mod.Core immunogen and the heterologous HxB2.WT.Core booster immunogen. We report that although the adjuvant used had no influence on the durability of plasma antibody responses after the prime, it influenced the plasma VRC01 antibody titers after the boost and the accumulation of somatic mutations on the elicited VRC01 antibodies.

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.

Human innate lymphoid cell activation by adenoviruses is modified by host defense proteins and neutralizing antibodies

Innate lymphoid cells (ILCs), the complements of diverse CD4 T helper cells, help maintain tissue homeostasis by providing a link between innate and adaptive immune responses. While pioneering studies over the last decade have advanced our understanding how ILCs influence adaptive immune responses to pathogens, far less is known about whether the adaptive immune response feeds back into an ILC response. In this study, we isolated ILCs from blood of healthy donors, fine-tuned culture conditions, and then directly challenged them with human adenoviruses (HAdVs), with HAdVs and host defense proteins (HDPs) or neutralizing antibodies (NAbs), to mimic interactions in a host with pre-existing immunity. Additionally, we developed an ex vivo approach to identify how bystander ILCs respond to the uptake of HAdVs ± neutralizing antibodies by monocyte-derived dendritic cells. We show that ILCs take up HAdVs, which induces phenotypic maturation and cytokine secretion. Moreover, NAbs and HDPs complexes modified the cytokine profile generated by ILCs, consistent with a feedback loop for host antiviral responses and potential to impact adenovirus-based vaccine efficacy.

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.

Glycan shield of the ebolavirus envelope glycoprotein GP

The envelope glycoprotein GP of the ebolaviruses is essential for host cell entry and the primary target of the host antibody response. GP is heavily glycosylated with up to 17 N-linked sites, numerous O-linked glycans in its disordered mucin-like domain (MLD), and three predicted C-linked mannosylation sites. Glycosylation is important for host cell attachment, GP stability and fusion activity, and shielding from neutralization by serum antibodies. Here, we use glycoproteomics to profile the site-specific glycosylation patterns of ebolavirus GP. We detect up to 16 unique O-linked glycosylation sites in the MLD, and two O-linked sites in the receptor-binding GP1 subunit. Multiple O-linked glycans are observed within N-linked glycosylation sequons, suggesting crosstalk between the two types of modifications. We confirmed C-mannosylation of W288 in full-length trimeric GP. We find complex glycosylation at the majority of N-linked sites, while the conserved sites N257 and especially N563 are enriched in unprocessed glycans, suggesting a role in host-cell attachment via DC-SIGN/L-SIGN. Our findings illustrate how N-, O-, and C-linked glycans together build the heterogeneous glycan shield of GP, guiding future immunological studies and functional interpretation of ebolavirus GP-antibody interactions.

Site-specific N-, O-, and C-linked glycans are characterized in the ebolavirus envelope glycoprotein GP using mass spectrometry-based glycoproteomics.

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.

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.

Four Decades of Prophylactic EBV Vaccine Research: A Systematic Review and Historical Perspective

Background

Epstein-Barr virus (EBV) is the causal agent of infectious mononucleosis and has been associated with various cancers and autoimmune diseases. Despite decades of research efforts to combat this major global health burden, there is no approved prophylactic vaccine against EBV. To facilitate the rational design and assessment of an effective vaccine, we systematically reviewed pre-clinical and clinical prophylactic EBV vaccine studies to determine the antigens, delivery platforms, and animal models used in these studies.

Methods

We searched Cochrane Library, ClinicalTrials.gov, Embase, PubMed, Scopus, Web of Science, WHO’s Global Index Medicus, and Google Scholar from inception to June 20, 2020, for EBV prophylactic vaccine studies focused on humoral immunity.

Results

The search yielded 5,614 unique studies. 36 pre-clinical and 4 clinical studies were included in the analysis after screening against the exclusion criteria. In pre-clinical studies, gp350 was the most commonly used immunogen (33 studies), vaccines were most commonly delivered as monomeric proteins (12 studies), and mice were the most used animal model to test immunogenicity (15 studies). According to an adaptation of the CAMARADES checklist, 4 pre-clinical studies were rated as very high, 5 as high, 13 as moderate quality, 11 as poor, and 3 as very poor. In clinical studies, gp350 was the sole vaccine antigen, delivered in a vaccinia platform (1 study) or as a monomeric protein (3 studies). The present study was registered in PROSPERO (CRD42020198440).

Conclusions

Four major obstacles have prevented the development of an effective prophylactic EBV vaccine: undefined correlates of immune protection, lack of knowledge regarding the ideal EBV antigen(s) for vaccination, lack of an appropriate animal model to test vaccine efficacy, and lack of knowledge regarding the ideal vaccine delivery platform. Our analysis supports a multivalent antigenic approach including two or more of the five main glycoproteins involved in viral entry (gp350, gB, gH/gL, gp42) and a multimeric approach to present these antigens. We anticipate that the application of two underused challenge models, rhesus macaques susceptible to rhesus lymphocryptovirus (an EBV homolog) and common marmosets, will permit the establishment of in vivo correlates of immune protection and attainment of more generalizable data.

Systematic Review Registration

https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=198440, identifier PROSPERO I.D. CRD4202019844.

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.

Structural definition of a pan-sarbecovirus neutralizing epitope on the spike S2 subunit

Three betacoronaviruses have crossed the species barrier and established human-to-human transmission causing significant morbidity and mortality in the past 20 years. The most current and widespread of these is SARS-CoV-2. The identification of CoVs with zoonotic potential in animal reservoirs suggests that additional outbreaks could occur. Monoclonal antibodies targeting conserved neutralizing epitopes on diverse CoVs can form the basis for prophylaxis and therapeutic treatments and enable the design of vaccines aimed at providing pan-CoV protection. We previously identified a neutralizing monoclonal antibody, CV3-25 that binds to the SARS-CoV-2 spike, neutralizes the SARS-CoV-2 Beta variant comparably to the ancestral Wuhan Hu-1 strain, cross neutralizes SARS-CoV-1 and binds to recombinant proteins derived from the spike-ectodomains of HCoV-OC43 and HCoV-HKU1. Here, we show that the neutralizing activity of CV3-25 is maintained against the Alpha, Delta, Gamma and Omicron variants of concern as well as a SARS-CoV-like bat coronavirus with zoonotic potential by binding to a conserved linear peptide in the stem-helix region. Negative stain electron microscopy and a 1.74 Å crystal structure of a CV3-25/peptide complex demonstrates that CV3-25 binds to the base of the stem helix at the HR2 boundary to an epitope that is distinct from other stem-helix directed neutralizing mAbs.

A Neutralizing Antibody Targeting gH Provides Potent Protection against EBV Challenge In Vivo

Epstein-Barr virus (EBV) is an oncogenic herpesvirus that is associated with 200,000 new cases of cancer and 140,000 deaths annually. To date, there are no available vaccines or therapeutics for clinical usage. Recently, the viral heterodimer glycoprotein gH/gL has become a promising target for the development of prophylactic vaccines against EBV. Here, we developed the anti-gH antibody 6H2 and its chimeric version C6H2, which had full neutralizing activity in epithelial cells and partial neutralizing activity in B cells. C6H2 exhibited potent protection against lethal EBV challenge in a humanized mouse model. The cryo-electron microscopy (cryo-EM) structure further revealed that 6H2 recognized a previously unidentified epitope on gH/gL D-IV that is critical for viral attachment and subsequent membrane fusion with epithelial cells. Our results suggest that C6H2 is a promising candidate in the prevention of EBV-induced lymphoproliferative diseases (LPDs) and may inform the design of an EBV vaccine. IMPORTANCE Epstein-Barr virus (EBV) is a ubiquitous gammaherpesvirus that establishes lifelong persistence and is related to multiple diseases, including cancers. Neutralizing antibodies (NAbs) have proven to be highly effective in preventing EBV infection and subsequent diseases. Here, we developed an anti-EBV-gH NAb, 6H2, which blocked EBV infection in vitro and in vivo. This 6H2 neutralizing epitope should be helpful to understand EBV infection mechanisms and guide the development of vaccines and therapeutics against EBV infection.

C-type lectin-(like) fold - Protein-protein interaction patterns and utilization

The C-type lectin-like fold (CTL fold) is a building block of many proteins, including saccharide-binding lectins, natural killer cell receptors, macrophage mannose receptor, selectins, collectins, snake venoms and others. Some are important players in innate immunity and are involved in the first-line response to virally infected cells or cancer cells, some play a role in antimicrobial defense, and some are potential targets for fight against problems connected with allergies, obesity, and autoimmunity. The structure of a CTL domain typically contains two α-helices, two small β-sheets and a long surface loop, with two or three disulfide bridges stabilizing the structure. This small domain is often involved in interactions with a target molecule, however, utilizing varied parts of the domain surface, with or without structural modifications. More than 500 three-dimensional structures of CTL fold-containing proteins are available in the Protein Data Bank, including a significant number of complexes with their key interacting partners (protein:protein complexes). The amount of available structural data enables a detailed analysis of the rules of interaction patterns utilized in activation, inhibition, attachment and other pathways or functionalities. Interpretation of known CTL receptor structures and all other CTL-containing proteins and complexes with described three-dimensional structures, complemented with sequence/structure/interaction correlation analysis offers a comprehensive view of the rules of interaction patterns of the CTL fold. The results are of value for prediction of interaction behavior of so far not understood CTL-containing proteins and development of new protein binders based on this fold, with applications in biomedicine or biotechnologies. It follows from the available structural data that almost the whole surface of the CTL fold is utilized in protein:protein interactions, with the heaviest frequency of utilization in the canonical interaction region. The individual categories of interactions differ in the interface buildup strategy. The strongest CTL binders rely on interfaces with large interaction area, presence of hydrophobic core, or high surface complementarity. The typical interaction surfaces of the fold are not conserved in amino acid sequence and can be utilized in design of new binders for biotechnological applications.

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.

Antibody Generation and Immunogenicity Analysis of EBV gp42 N-Terminal Region

Epstein–Barr virus (EBV) is the first reported oncogenic virus and infects more than 90% of adults worldwide. EBV can establish a latent infection in B lymphocytes which is essential for persistence and transmission. Glycoprotein gp42 is an indispensable member of the triggering complex for EBV entry into a B cell. The N-terminal region of gp42 plays a key role in binding to gH/gL and triggering subsequent membrane fusion. However, no antibody has been reported to recognize this region and the immunogenicity of gp42 N-domain remains unknown. In the present study, we have generated a panel of nine mAbs against the gp42 N-terminal region (six mAbs to gp42-44-61aa and three mAbs to gp42-67-81aa). These mAbs show excellent binding activity and recognize different key residues locating on the gp42 N-domain. Among the nine mAbs, 4H7, 4H8 and 11G10 cross-react with rhLCV-gp42 while other mAbs specifically recognize EBV-gp42. Our newly obtained mAbs provide a useful tool for investigating the gp42 function and viral infection mechanism of γ-Herpesvirus. Furthermore, we assess the immunogenicity of the gp42 N-terminal region using the HBc149 particle as a carrier protein. The chimeric VLPs can induce high antibody titers and elicit neutralizing humoral responses to block EBV infection. More rational and effective designs are required to promote the gp42-N terminal region to become an epitope-based vaccine.

Potential entry receptors for human γ-herpesvirus into epithelial cells: A plausible therapeutic target for viral infections

Herpesviruses are ubiquitous viruses, specifically the Epstein Barr virus (EBV). EBV and Kaposi's sarcoma-associated herpesvirus (KSHV) establish their latency for a long period in B-cells and their reactivation instigates dreadful diseases from cancer to neurological modalities. The envelope glycoprotein of these viruses makes an attachment with several host receptors. For instance; glycoprotein 350/220, gp42, gHgL and gB of EBV establish an attachment with CD21, HLA-DR, Ephs, and other receptor molecules to hijack the B- and epithelial cell machinery. Ephs are reported recently as potent receptors for EBV entry into epithelial cells. Eph receptors play a role in the maintenance and control of various cellular processes including morphology, adhesion, proliferation, survival and differentiation. Alterations in the structure and expression of Eph and ephrin (Eph ligands) molecules is entangled with various pathologies including tumours and neurological complications. Along with Eph, integrins, NRP, NMHC are also key players in viral infections as they are possibly involved in viral transmission, replication and persistence. Contrarily, KSHV gH is known to interact with EphA2 and -A4 molecules, whereas in the case of EBV only EphA2 receptors are being reported to date. The ELEFN region of KSHV gH was involved in the interaction with EphA2, however, the interacting region of EBV gH is elusive. Further, the gHgL of KSHV and EBV form a complex with the EphA2 ligand-binding domain (LBD). Primarily by using gL both KSHV and EBV gHgL bind to the peripheral regions of LBD. In addition to γ-herpesviruses, several other viruses like Nipah virus, Cedar virus, Hepatitis C virus and Rhesus macaque rhadinovirus (RRV) also access the host cells via Eph receptors. Therefore, we summarise the possible roles of Eph and ephrins in virus-mediated infection and these molecules could serve as potential therapeutic targets.

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Crucial understanding of human γ-herpesviruses entry mechanism.

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Eph receptors relate to changed biomolecular profile upon EBV infection.

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EBV association with neurological disorders.

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Eph receptors could be an elegant drug for human γ-herpesviruses.

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

Epstein-Barr virus (EBV) is associated with a range of epithelial and B cell malignancies as well as autoimmune disorders, for which there are still no specific treatments or effective vaccines. Here, we isolate EBV gH/gL-specific antibodies from an EBV-infected individual. One antibody, 1D8, efficiently neutralizes EBV infection of two major target cell types, B cells and epithelial cells. In humanized mice, 1D8 provides protection against a high-dose EBV challenge by substantially reducing viral loads and associated tumor burden. Crystal structure analysis reveals that 1D8 binds to a key vulnerable interface between the D-I/D-II domains of the viral gH/gL protein, especially the D-II of the gH, thereby interfering with the gH/gL-mediated membrane fusion and binding to target cells. Overall, we identify a potent and protective neutralizing antibody capable of reducing the EBV load. The novel vulnerable site represents an attractive target that is potentially important for antibody and vaccine intervention against EBV infection.

Advances in pathogenesis and precision medicine for nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is a squamous carcinoma with apparent geographical and racial distribution, mostly prevalent in East and Southeast Asia, particularly concentrated in southern China. The epidemiological trend over the past decades has suggested a substantial reduction in the incidence rate and mortality rate due to NPC. These results may reflect changes in lifestyle and environment, and more importantly, a deeper comprehension of the pathogenic mechanism of NPC, leading to much progress in the preventing, screening, and treating for this cancer. Herein, we present the recent advances on the key signal pathways involved in pathogenesis of NPC, the mechanism of Epstein‐Barr virus (EBV) entry into the cell, and the progress of EBV vaccine and screening biomarkers. We will also discuss in depth the development of various therapeutic approaches including radiotherapy, chemotherapy, surgery, targeted therapy, and immunotherapy. These research advancements have led to a new era of precision medicine in NPC.

Prophylactic and Therapeutic EBV Vaccines: Major Scientific Obstacles, Historical Progress, and Future Direction

The Epstein-Barr virus (EBV) infects more than 95% of adults worldwide and is associated with various malignant tumors and immune diseases, imparting a huge disease burden on the human population. Available EBV vaccines are imminent. Prophylactic vaccines can effectively prevent the spread of infection, whereas therapeutic vaccines mainly stimulate cell-mediated immunity and kill infected cells, thus curbing the development of malignant tumors. Nevertheless, there are still no approved EBV vaccines after decades of effort. The complexity of the EBV life cycle, the lack of appropriate animal models, and the limited reports on adjuvant selection and immune responses are gravely impeding progress in EBV vaccines. The soluble gp350 vaccine could reduce the incidence of infectious mononucleosis (IM), which seemed to offer hope, but could not prevent EBV infection. Continuous research and vaccine trials provide deep insights into the structural biology of viruses, the designs for immunogenicity, and the evolving vaccine platforms. Moreover, the new vaccine candidates are expected to achieve further success via combined immunization to elicit both a dual protection of B cells and epithelial cells, and sustainable immunization against infected cells at several phases of infection.

Representing and Comparing Site-Specific Glycan Abundance Distributions of Glycoproteins

A method for representing and comparing distributions of N-linked glycans located at specific sites on proteins is presented. The representation takes the form of a simple mass spectrum for a given peptide sequence, with each peak corresponding to a different glycopeptide. The mass (in place of m/z) of each peak is that of the glycan mass, and its abundance corresponds to its relative abundance in the electrospray MS¹ spectrum. This provides a facile means of representing all identifiable glycopeptides arising from a single protein "sequon" on a specific sequence, thereby enabling the comparison and searching of these distributions as routinely done for mass spectra. Likewise, these reference glycopeptide abundance distribution spectra (GADS) can be stored in searchable libraries. A set of such libraries created from available data is provided along with an adapted version of the widely used NIST-MS library-search software. Since GADS contain only MS¹ abundances and identifications, they are equally suitable for expressing collision-induced fragmentation and electron-transfer dissociation determinations of glycopeptide identity. Comparisons of GADS for N-glycosylated sites on several proteins, especially the SARS-CoV-2 spike protein, demonstrate the potential reproducibility of GADS and their utility for comparing site-specific distributions.

Epstein-Barr virus (EBV) hyperimmune globulin isolated from donors with high gp350 antibody titers protect humanized mice from challenge with EBV

Primary infection with Epstein-Barr virus (EBV) is 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. Hyperimmune globulin has been used to prevent some virus infections in immunocompromised persons. Here, we identified plasma donors with high titers of EBV gp350 and EBV B cell neutralizing antibodies. Pooled IgG isolated from these donors was compared to intravenous immunoglobulin (IVIG) for its ability to reduce viral load in the blood in humanized mice challenged with EBV. Mice that received EBV hyperimmune globulin had significantly reduced EBV DNA copy numbers compared to animals that received saline control; however, while animals that received EBV hyperimmune globulin had lower EBV DNA copies than those that received IVIG, the difference was not significant. Thus, while EBV hyperimmune globulin reduced viral load compared to IVIG, the effect was modest.

Neutralizing antibodies against Epstein-Barr virus infection of B cells can protect from oral viral challenge in the rhesus macaque animal model

Epstein-Barr virus (EBV) and related lymphocryptoviruses (LCVs) from nonhuman primates are transmitted through oral secretions, penetrate the mucosal epithelium, and establish persistent infection in B cells. To determine whether neutralizing antibodies against epithelial or B cell infection could block oral transmission and persistent LCV infection, we use rhesus macaques, the most accurate animal model for EBV infection by faithfully reproducing acute and persistent infection in humans. Naive animals are infused with monoclonal antibodies neutralizing epithelial cell infection or B cell infection and then challenged orally with recombinant rhesus LCV. Our data show that high-titer B cell-neutralizing antibodies alone, but not epithelial cell-neutralizing antibodies, can provide complete protection of rhesus macaques from oral LCV challenge, but not in all hosts. Thus, neutralizing antibodies against B cell infection are important targets for EBV vaccine development, but they may not be sufficient.

mAb infusion leads to high neutralizing titers in nonhuman primates

Protection of epithelial cells does not protect from lymphocryptovirus challenge

Neutralization of B cell infection alone provides partial protection in macaques

Isolation and characterization of cross-neutralizing coronavirus antibodies from COVID-19+ subjects

SARS-CoV-2 is one of three coronaviruses that have crossed the animal-to-human barrier and caused widespread disease in the past two decades. The development of a universal human coronavirus vaccine could prevent future pandemics. We characterize 198 antibodies isolated from four COVID-19+ subjects and identify 14 SARS-CoV-2 neutralizing antibodies. One targets the N-terminal domain (NTD), one recognizes an epitope in S2, and 11 bind the receptor-binding domain (RBD). Three anti-RBD neutralizing antibodies cross-neutralize SARS-CoV-1 by effectively blocking binding of both the SARS-CoV-1 and SARS-CoV-2 RBDs to the ACE2 receptor. Using the K18-hACE transgenic mouse model, we demonstrate that the neutralization potency and antibody epitope specificity regulates the in vivo protective potential of anti-SARS-CoV-2 antibodies. All four cross-neutralizing antibodies neutralize the B.1.351 mutant strain. Thus, our study reveals that epitopes in S2 can serve as blueprints for the design of immunogens capable of eliciting cross-neutralizing coronavirus antibodies.

Main Targets of Interest for the Development of a Prophylactic or Therapeutic Epstein-Barr Virus Vaccine

Epstein-Barr virus (EBV) is one of the most widespread viruses in the world; more than 90% of the planet's adult population is infected. Symptomatic primary infection by this Herpesviridae corresponds to infectious mononucleosis (IM), which is generally a benign disease. While virus persistence is often asymptomatic, it is responsible for 1.5% of cancers worldwide, mainly B cell lymphomas and carcinomas. EBV may also be associated with autoimmune and/or inflammatory diseases. However, no effective treatment or anti-EBV vaccine is currently available. Knowledge of the proteins and mechanisms involved in the different steps of the viral cycle is essential to the development of effective vaccines. The present review describes the main actors in the entry of the virus into B cells and epithelial cells, which are targets of interest in the development of prophylactic vaccines aimed at preventing viral infection. This review also summarizes the first vaccinal approaches tested in humans, all of which are based on the gp350/220 glycoprotein; while they have reduced the risk of IM, they have yet to prevent EBV infection. The main proteins involved in the EBV latency cycle and some of the proteins involved in the lytic cycle have essential roles in the oncogenesis of EBV. For that reason, these proteins are of interest for the development of therapeutic vaccines of which the objective is the stimulation of T cell immunity against EBV-associated cancers. New strategies aimed at broadening the antigenic spectrum, are currently being studied and will contribute to the targeting of the essential steps of the viral cycle, the objective being to prevent or treat the diseases associated with EBV.

The Status and Prospects of Epstein-Barr Virus Prophylactic Vaccine Development

Epstein–Barr virus (EBV) is a human herpesvirus that is common among the global population, causing an enormous disease burden. EBV can directly cause infectious mononucleosis and is also associated with various malignancies and autoimmune diseases. In order to prevent primary infection and subsequent chronic disease, efforts have been made to develop a prophylactic vaccine against EBV in recent years, but there is still no vaccine in clinical use. The outbreak of the COVID-19 pandemic and the global cooperation in vaccine development against SARS-CoV-2 provide insights for next-generation antiviral vaccine design and opportunities for developing an effective prophylactic EBV vaccine. With improvements in antigen selection, vaccine platforms, formulation and evaluation systems, novel vaccines against EBV are expected to elicit dual protection against infection of both B lymphocytes and epithelial cells. This would provide sustainable immunity against EBV-associated malignancies, finally enabling the control of worldwide EBV infection and management of EBV-associated diseases.

A conditionally replication-defective cytomegalovirus vaccine elicits potent and diverse functional monoclonal antibodies in a phase I clinical trial

A conditionally replication-defective human cytomegalovirus (HCMV) vaccine, V160, was shown to be safe and immunogenic in a two-part, double-blind, randomized, placebo-controlled phase I clinical trial (NCT01986010). However, the specificities and functional properties of V160-elicited antibodies remain undefined. Here, we characterized 272 monoclonal antibodies (mAbs) isolated from single memory B cells of six V160-vaccinated subjects. The mAbs bind to diverse HCMV antigens, including multiple components of the pentamer, gB, and tegument proteins. The most-potent neutralizing antibodies target the pentamer-UL subunits. The binding sites of the antibodies overlap with those of antibodies responding to natural HCMV infection. The majority of the neutralizing antibodies target the gHgL subunit. The non-neutralizing antibodies predominantly target the gB and pp65 proteins. Sequence analysis indicated that V160 induced a class of gHgL antibodies expressing the HV1-18/KV1-5 germline genes in multiple subjects. This study provides valuable insights into primary targets for anti-HCMV antibodies induced by V160 vaccination.

Structural basis for broad coronavirus neutralization

Three highly pathogenic β-coronaviruses have crossed the animal-to-human species barrier in the past two decades: SARS-CoV, MERS-CoV and SARS-CoV-2. To evaluate the possibility of identifying antibodies with broad neutralizing activity, we isolated a monoclonal antibody, termed B6, that cross-reacts with eight β-coronavirus spike glycoproteins, including all five human-infecting β-coronaviruses. B6 broadly neutralizes entry of pseudotyped viruses from lineages A and C, but not from lineage B, and the latter includes SARS-CoV and SARS-CoV-2. Cryo-EM, X-ray crystallography and membrane fusion assays reveal that B6 binds to a conserved cryptic epitope located in the fusion machinery. The data indicate that antibody binding sterically interferes with the spike conformational changes leading to membrane fusion. Our data provide a structural framework explaining B6 cross-reactivity with β-coronaviruses from three lineages, along with a proof of concept for antibody-mediated broad coronavirus neutralization elicited through vaccination. This study unveils an unexpected target for next-generation structure-guided design of a pan-β-coronavirus vaccine.

Development of a VRC01-class germline targeting immunogen derived from anti-idiotypic antibodies

An effective HIV-1 vaccine will likely need to elicit broadly neutralizing antibodies (bNAbs). Broad and potent VRC01-class bNAbs have been isolated from multiple infected individuals, suggesting that they could be reproducibly elicited by vaccination. Several HIV-1 envelope-derived germline-targeting immunogens have been designed to engage naive VRC01-class precursor B cells. However, they also present off-target epitopes that could hinder development of VRC01-class bNAbs. We characterize a panel of anti-idiotypic monoclonal antibodies (ai-mAbs) raised against inferred-germline (iGL) VRC01-class antibodies. By leveraging binding, structural, and B cell sorting data, we engineered a bispecific molecule derived from two ai-mAbs; one specific for VRC01-class heavy chains and one specific for VRC01-class light chains. The bispecific molecule preferentially activates iGL-VRC01 B cells in vitro and induces specific antibody responses in a murine adoptive transfer model with a diverse polyclonal B cell repertoire. This molecule represents an alternative non-envelope-derived germline-targeting immunogen that can selectively activate VRC01-class precursors in vivo.

HIV-1 VRC01 Germline-Targeting Immunogens Select Distinct Epitope-Specific B Cell Receptors

Activating precursor B cell receptors of HIV-1 broadly neutralizing antibodies requires specifically designed immunogens. Here, we compared the abilities of three such germline-targeting immunogens against the VRC01-class receptors to activate the targeted B cells in transgenic mice expressing the germline VH of the VRC01 antibody but diverse mouse light chains. Immunogen-specific VRC01-like B cells were isolated at different time points after immunization, their VH and VL genes were sequenced, and the corresponding antibodies characterized. VRC01 B cell sub-populations with distinct cross-reactivity properties were activated by each immunogen, and these differences correlated with distinct biophysical and biochemical features of the germline-targeting immunogens. Our study indicates that the design of effective immunogens to activate B cell receptors leading to protective HIV-1 antibodies will require a better understanding of how the biophysical properties of the epitope and its surrounding surface on the germline-targeting immunogen influence its interaction with the available receptor variants in vivo.

mRNA vaccination boosts cross-variant neutralizing antibodies elicited by SARS-CoV-2 infection

Emerging SARS-CoV-2 variants have raised concerns about resistance to neutralizing antibodies elicited by previous infection or vaccination. We examined whether sera from recovered and naïve donors collected prior to, and following immunizations with existing mRNA vaccines, could neutralize the Wuhan-Hu-1 and B.1.351 variants. Pre-vaccination sera from recovered donors neutralized Wuhan-Hu-1 and sporadically neutralized B.1.351, but a single immunization boosted neutralizing titers against all variants and SARS-CoV-1 by up to 1000-fold. Neutralization was due to antibodies targeting the receptor binding domain and was not boosted by a second immunization. Immunization of naïve donors also elicited cross-neutralizing responses, but at lower titers. Our study highlights the importance of vaccinating both uninfected and previously infected persons to elicit cross-variant neutralizing antibodies.