High Epstein-Barr Virus Load and Genomic Diversity Are Associated with Generation of gp350-Specific Neutralizing Antibodies following Acute Infectious Mononucleosis

Genomic diversity and natural recombination of equid gammaherpesvirus 5 isolates

BACKGROUND

Equid gammaherpesvirus 5 (EHV5) is closely related to equid gammaherpesvirus 2 (EHV2). Detection of EHV5 is frequent in horse populations worldwide, but it is often without a clear and significant clinical impact. Infection in horses can often present as subclinical disease; however, it has been associated with respiratory disease, including equine multinodular pulmonary fibrosis (EMPF). Genetic heterogeneity within small regions of the EHV5 glycoprotein B (gB) sequences have been reported and multiple genotypes of this virus have been identified within individual horses, but full genome sequence data for these viruses is limited. The primary focus of this study was to assess the genomic diversity and natural recombination among EHV5 isolates.

RESULTS

The genome size of EHV5 prototype strain and the five EHV5 isolates cultured for this study, including four isolates from the same horse, ranged from 181,929 to 183,428 base pairs (bp), with the sizes of terminal repeat regions varying from 0 to 10 bp. The nucleotide sequence identity between the six EHV5 genomes ranged from 95.5 to 99.1%, and the estimated average nucleotide diversity between isolates was 1%. Individual genes displayed varying levels of nucleotide diversity that ranged from 0 to 19%. The analysis of nonsynonymous substitution (Ka > 0.025) revealed high diversity in eight genes. Genome analysis using RDP4 and SplitsTree programs detected evidence of past recombination events between EHV5 isolates.

CONCLUSION

Genomic diversity and recombination hotspots were identified among EHV5 strains. Recombination can drive genetic diversity, particularly in viruses that have a low rate of nucleotide substitutions. Therefore, the results from this study suggest that recombination is an important contributing factor to EHV5 genomic diversity. The findings from this study provide additional insights into the genetic heterogeneity of the EHV5 genome.

Lymph node targeted multi-epitope subunit vaccine promotes effective immunity to EBV in HLA-expressing mice

The recent emergence of a causal link between Epstein-Barr virus (EBV) and multiple sclerosis has generated considerable interest in the development of an effective vaccine against EBV. Here we describe a vaccine formulation based on a lymph node targeting Amphiphile vaccine adjuvant, Amphiphile-CpG, admixed with EBV gp350 glycoprotein and an engineered EBV polyepitope protein that includes 20 CD8+ T cell epitopes from EBV latent and lytic antigens. Potent gp350-specific IgG responses are induced in mice with titers >100,000 in Amphiphile-CpG vaccinated mice. Immunization including Amphiphile-CpG also induces high frequencies of polyfunctional gp350-specific CD4+ T cells and EBV-specific CD8+ T cells that are 2-fold greater than soluble CpG and are maintained for >7 months post immunization. This combination of broad humoral and cellular immunity against multiple viral determinants is likely to provide better protection against primary infection and control of latently infected B cells leading to protection against the development of EBV-associated diseases.

Virological Markers in Epstein–Barr Virus-Associated Diseases

Epstein–Barr virus (EBV) is an oncogenic virus infecting more than 95% of the world’s population. After primary infection—responsible for infectious mononucleosis in young adults—the virus persists lifelong in the infected host, especially in memory B cells. Viral persistence is usually without clinical consequences, although it can lead to EBV-associated cancers such as lymphoma or carcinoma. Recent reports also suggest a link between EBV infection and multiple sclerosis. In the absence of vaccines, research efforts have focused on virological markers applicable in clinical practice for the management of patients with EBV-associated diseases. Nasopharyngeal carcinoma is an EBV-associated malignancy for which serological and molecular markers are widely used in clinical practice. Measuring blood EBV DNA load is additionally, useful for preventing lymphoproliferative disorders in transplant patients, with this marker also being explored in various other EBV-associated lymphomas. New technologies based on next-generation sequencing offer the opportunity to explore other biomarkers such as the EBV DNA methylome, strain diversity, or viral miRNA. Here, we review the clinical utility of different virological markers in EBV-associated diseases. Indeed, evaluating existing or new markers in EBV-associated malignancies or immune-mediated inflammatory diseases triggered by EBV infection continues to be a challenge.

[Epstein-Barr viral infection is a global epidemiological problem]

The number of studies devoted to Epstein-Barr viral infection (EBV infection) has been growing in recent years. However, they all relate to the clinical aspects of this problem. Epidemiology issues remain practically unexplored. A review of domestic and foreign publications has shown that at the present stage there is a high intensity of the epidemic process of EBV infection both in Russia and abroad. The main indicators of unfavorable epidemiological situation are the ubiquitous spread of the pathogen and the increase in the incidence of infectious mononucleosis in recent years. The deterioration of the epidemic situation of EBV infection is influenced by changes in the immunological reactivity of various population groups due to the spread of HIV, HBV, HCV, the causative agent of tuberculosis and SARS-CoV-2. The above makes it possible to classify the problem as a global one and determines the need for the rapid implementation of the system of epidemiological surveillance of EBV infection and optimization of the complex of preventive and anti-epidemic measures. Reducing the burden of EBV is possible only with the consolidated participation of specialists of various profiles.

Evolution of functional antibodies following acute Epstein-Barr virus infection

While Epstein-Barr virus causes mostly asymptomatic infection, associated malignancies, and autoimmune and lymphoproliferative diseases occur. To dissect the evolution of humoral immune responses over the course of EBV infection and to gain a better understanding of the potential contribution of antibody (Ab) function to viral control, we comprehensively profiled Ab specificities and Fc-functionalities using systems serology and VirScan. Ab functions against latent (EBNA1), early (p47/54) and two late (gp350/220 and VCA-p18) EBV proteins were overall modest and/or short-lived, differing from humoral responses induced during acute infection by other viruses such as HIV. In the first year post infection, only p18 elicited robust IgM-driven complement deposition and IgG-driven neutrophil phagocytosis while responses against EBNA-1 were largely Fc-functionally silent and only matured during chronic infection to drive phagocytosis. In contrast, Abs against Influenza virus readily mediated broad Fc-activity in all participants. These data suggest that EBV evades the induction of robust Fc-functional Abs, potentially due to the virus’ life cycle, switching from lytic to latent stages during infection.

While previously thought to be largely innocuous, emerging data clearly highlight the pathological role of lifelong EBV infection in driving autoimmunity and malignancies in a small, but not insignificant portion of the population. We therefore aimed to define potential humoral mechanisms associated with viral control, beyond neutralizing Abs, by systematically focusing on antibody Fc-functional activities during acute to convalescent EBV infection applying technologies such as systems serology and VirScan. We found that functions against EBV proteins were overall only modest and either short-lived or delayed, differing from functional antibody responses induced during acute infection by other viruses such as HIV. These data suggest that EBV evades the induction of robust Fc-functional Abs thereby potentially facilitating lifelong, persistent infection with all its consequences.

Serum IgG levels to Epstein-Barr and measles viruses in patients with multiple sclerosis during natalizumab and interferon beta treatment

Background

Patients with multiple sclerosis (MS) demonstrate higher seroprevalence of Epstein-Barr virus (EBV) and increased anti-EBV IgG levels in serum compared with healthy controls. Intrathecal antibody production to measles virus (MeV) is a common finding in patients with MS.

Objective

To measure serum IgG reactivity to EBV glycoprotein 350 (gp350) and MeV nucleocapsid protein (N_CORE) in patients with MS and healthy controls and to determine if reactivity changed in patients during interferon beta (IFNβ) and/or natalizumab (NAT) treatment. A secondary aim was to determine the seroprevalence of EBV in patients and controls.

Methods

Patients with MS (n=728) were included from the Swedish pharmacovigilance study for NAT. Paired serum samples from 714 patients drawn before and during NAT treatment and paired samples from 170 patients during prior IFNβ treatment were analysed. In total, 156 patients were included in both groups. Samples from 144 matched blood donors served as controls. Indirect ELISA was applied using recombinant EBVgp350 and MeV N_CORE as antigens. EBVgp350 IgG seronegative samples were also analysed using EBV nuclear antigen 1 and viral capsid antigen (VCA).

Results

Patients with MS showed higher serum levels of anti-EBVgp350 and anti-MeV N_CORE IgG compared with controls. During NAT treatment, the levels of anti-EBVgp350 and anti-MeV N_CORE IgG declined, compared with the relatively stable levels noted during prior IFNβ treatment. Ten patients failed to demonstrate anti-EBVgp350 IgG but did show detectable anti-VCA IgG, indicating EBV seropositivity. In contrast, 10/144 controls were EBV seronegative.

Conclusions

Treatment with NAT, which is considered a selective immunosuppressive agent with a compartmentalised effect on the central nervous system, appeared to be associated with a moderate decrease in circulating IgG levels to EBVgp350 and MeV N_CORE. All patients with MS were EBV IgG seropositive, supporting the potential role of EBV in the pathogenesis of MS.

Cross-reactivity influences changes in human influenza A virus and Epstein Barr virus specific CD8 memory T cell receptor alpha and beta repertoires between young and old

Older people have difficulty controlling infection with common viruses such as influenza A virus (IAV), RNA virus which causes recurrent infections due to a high rate of genetic mutation, and Epstein Barr virus (EBV), DNA virus which persists in B cells for life in the 95% of people that become acutely infected. We questioned whether changes in epitope-specific memory CD8 T cell receptor (TCR) repertoires to these two common viruses could occur with increasing age and contribute to waning immunity. We compared CD8 memory TCR alpha and beta repertoires in two HLA-A2+ EBV- and IAV-immune donors, young (Y) and older (O) donors to three immunodominant epitopes known to be cross-reactive, IAV-M1_58-66 (IAV-M1), EBV-BMLF1_280-288 (EBV-BM), and EBV-BRLF1_109-117 (EBV-BR). We, therefore, also designed these studies to examine if TCR cross-reactivity could contribute to changes in repertoire with increasing age. TCR high throughput sequencing showed a significant difference in the pattern of TRBV usage between Y and O. However, there were many more differences in AV and AJ usage, between the age groups suggesting that changes in TCRα usage may play a greater role in evolution of the TCR repertoire emphasizing the importance of studying TRAV repertoires. With increasing age there was a preferential retention of TCR for all three epitopes with features in their complementarity-determining region (CDR3) that increased their ease of generation, and their cross-reactive potential. Young and older donors differed in the patterns of AV/AJ and BV/BJ pairings and usage of dominant CDR3 motifs specific to all three epitopes. Both young and older donors had cross-reactive responses between these 3 epitopes, which were unique and differed from the cognate responses having features that suggested they could interact with either ligand. There was an increased tendency for the classic IAV-M1 specific clone BV19-IRSS-JB2.7/AV27-CAGGGSQGNLIF-AJ42 to appear among the cross-reactive clones, suggesting that the dominance of this clone may relate to its cross-reactivity with EBV. These results suggest that although young and older donors retain classic TCR features for each epitope their repertoires are gradually changing with age, maintaining TCRs that are cross-reactive between these two common human viruses, one with recurrent infections and the other a persistent virus which frequently reactivates.

Follow-up after infectious mononucleosis in search of serological similarities with presymptomatic multiple sclerosis

BACKGROUND

A two- to three-fold increase in the risk of multiple sclerosis (MS) after infectious mononucleosis (IM) has been observed in cohort and case control studies. However, this association has not been investigated prospectively from IM. It remains to be determined whether long-term immunospecific sequelae with features consistent with presymptomatic MS occur after IM.

METHODS

Sera were obtained from individuals with acute IM from 2003-2007 (n = 42) and from the same individuals at a follow-up (FU) study approximately 10 years after IM. These were assayed for antibodies against a variety of Epstein-Barr virus (EBV) antigens, including gp350, a novel recombinant glycoprotein from the EBV envelope. Similarly, single-protein antigens were used to assess measles and varicella-zoster reactivity (Ncore and varicella-zoster glycoprotein E [VZVgE]). The FU study also included cerebrospinal fluid (CSF) samples from 21 of these individuals to test for IgG antibodies against the same viral antigens. As controls, CSF and serum samples were obtained from 15 EBV-seropositive volunteers who denied a history of IM, and serum samples were obtained from 24 EBV-seropositive blood donors. Anti-gp350, anti-Ncore and anti-VZVgE IgG levels were also analysed in sera and CSF samples from 22 persons with MS.

RESULTS

The FU assays showed higher anti-gp350 IgG (p = 0.007, univariate) than among healthy controls, with no difference in serum anti-VCA or anti-EBNA1 IgG levels and no difference in anti-gp350 in the CSF samples. Anti-Ncore IgG and anti-VZVgE were higher in acute IM samples (p < 0.001 and p < 0.0001, respectively) than at FU, although anti-Ncore remained heightened in an age-adjusted analysis at FU (p = 0.014) compared to the control group. In the MS group, the serum anti-gp350 and anti-Ncore IgG levels were significantly higher than among the control group, but the anti-VZVgE levels were not. The CSF anti-gp350 and VZVgE levels were slightly higher among persons with MS than among the control group, whereas anti-Ncore IgG was markedly higher in persons with MS than in the control group.

CONCLUSION

In the present study IM showed certain similarities with MS. Increased anti-gp350 reactivity persisted more than a decade after IM, reminiscent of the established increased anti-EBV reactivity in presymptomatic MS. Acute IM was associated with increased anti-measles and anti-VZV immunoreactivity, similar to the MRZ reaction in MS, with some evidence suggesting that this measles reactivity persisted after a decade.

Stress-Induced Epstein-Barr Virus Reactivation

Epstein-Barr virus (EBV) is typically found in a latent, asymptomatic state in immunocompetent individuals. Perturbations of the host immune system can stimulate viral reactivation. Furthermore, there are a myriad of EBV-associated illnesses including various cancers, post-transplant lymphoproliferative disease, and autoimmune conditions. A thorough understanding of this virus, and the interplay between stress and the immune system, is essential to establish effective treatment. This review will provide a summary of the interaction between both psychological and cellular stressors resulting in EBV reactivation. It will examine mechanisms by which EBV establishes and maintains latency and will conclude with a brief overview of treatments targeting EBV.

Targeted Therapies for Epstein-Barr Virus-Associated Lymphomas

Simple Summary

Epstein-Barr virus (EBV) is the first-discovered and important human tumor virus. It infects more than 90% of human population and induces various lymphomas. Development of specific targeted therapies is very critical for treatment of EBV-induced lymphomas, but it remains a great challenge. In this review, we introduced the current progress of EBV-specific therapies and the promising approaches that can be developed as novel targeted therapies, which involve protective or therapeutic strategies to target these lymphomas on different levels. This work will provide new insights into the development of new targeted therapies against EBV-associated lymphomas.

Abstract

The Epstein-Barr virus (EBV) is the first human tumor virus identified that can transform quiescent B lymphocytes into lymphoblastoid cell lines (LCLs) in vitro. EBV can establish asymptomatic life-long persistence and is associated with multiple human malignancies, including non-Hodgkin lymphoma and Hodgkin lymphoma, as well as infectious mononucleosis. Although EBV-associated lymphomagenesis has been investigated for over 50 years, viral-mediated transformation is not completely understood, and the development of EBV-specific therapeutic strategies to treat the associated cancers is still a major challenge. However, the rapid development of several novel therapies offers exciting possibilities to target EBV-induced lymphomas. This review highlights targeted therapies with potential for treating EBV-associated lymphomas, including small molecule inhibitors, immunotherapy, cell therapy, preventative and therapeutic vaccines, and other potent approaches, which are novel strategies for controlling, preventing, and treating these viral-induced malignances.

Recombinant Epstein-Barr virus glycoprotein 350 as a serological antigen

Epstein-Barr virus (EBV) glycoprotein 350 (gp350) is the most abundant glycoprotein expressed on the EBV envelope, the major target for neutralizing antibodies and also essential for virion attachment to B lymphocytes. Several studies have addressed EBV gp350 as a vaccine candidate, but less commonly as a potential antigen for serological assays. The aim of the current study was to develop a diagnostic tool to quantify EBV gp350-specific IgG in previously EBV-infected individuals. A construct encoding the extracellular domain of EBV gp350 (amino acid (aa) 1-860) was developed for expression in Chinese hamster ovary cells. Serum samples (n = 360) with known IgG serostatus against viral capsid antigen (VCA) and Epstein-Barr nuclear antigen 1 (EBNA1) were divided into three groups based on the differences in their serostatus: VCA + EBNA1+ (n = 120), VCA + EBNA1- (n = 120) and VCA-EBNA1- (n = 120). The samples were analyzed by indirect ELISA using recombinant EBV gp350 aa 1-860 as antigen. A clear majority, 108 of the 120 VCA + EBNA1+ samples, had detectable EBV gp350-specific IgG. Of the 120 VCA + EBNA1- samples, 79 had detectable EBV gp350-specific IgG. Only 2 of the 120 VCA-EBNA1- samples had detectable EBV gp350-specific IgG. The results reported here show that use of the EBV gp350 aa 1-860 ELISA can serve as a sensitive method for EBV-specific IgG detection in serum samples.

CD21 (Complement Receptor 2) Is the Receptor for Epstein-Barr Virus Entry into T Cells

Epstein-Barr virus (EBV) is associated with a number of T-cell diseases, including some peripheral T-cell lymphomas, hemophagocytic lymphohistiocytosis, and chronic active EBV disease. The tropism of EBV for B cells and epithelial cell infection has been well characterized, but infection of T cells has been minimally explored. We have recently shown that the EBV type 2 (EBV-2) strain has the unique ability to infect mature T cells. Utilizing an ex vivo infection model, we sought to understand the viral glycoprotein and cellular receptor required for EBV-2 infection of T cells. Here, using a neutralizing-antibody assay, we found that viral gp350 and complement receptor 2 (CD21) are required for CD3⁺ T-cell infection. Using the HB5 anti-CD21 antibody clone but not the Bly-4 anti-CD21 antibody clone, we detected expression of CD21 on both CD4⁺ and CD8⁺ T cells, with the highest expression on naive CD4 and CD8⁺ T-cell subsets. Using CRISPR to knock out CD21, we demonstrated that CD21 is necessary for EBV entry into the Jurkat T-cell line. Together, these results indicate that EBV uses the same viral glycoprotein and cellular receptor for both T- and B-cell infection.IMPORTANCE Epstein-Barr virus (EBV) has a well-described tropism for B cells and epithelial cells. Recently, we described the ability of a second strain of EBV, EBV type 2, to infect mature peripheral T cells. Using a neutralizing antibody assay, we determined that EBV uses the viral glycoprotein gp350 and the cellular protein CD21 to gain entry into mature peripheral T cells. CRISPR-Cas9 deletion of CD21 on the Jurkat T-cell line confirmed that CD21 is required for EBV infection. This study has broad implications, as we have defined a function for CD21 on mature peripheral T cells, i.e., as a receptor for EBV. In addition, the requirement for gp350 for T-cell entry has implications for EBV vaccine studies currently targeting the gp350 glycoprotein to prevent EBV-associated diseases.

Differences in the Epstein-Barr Virus gp350 IgA Antibody Response Are Associated With Increased Risk for Coinfection With a Second Strain of Epstein-Barr Virus

BACKGROUND

The Epstein-Barr virus (EBV) viral glycoprotein gp350 has been proposed as a candidate antigen for an EBV vaccine. However, the proposed formulations of these vaccines have not taken into account the presence of 2 unique EBV strains (EBV-1 and EBV-2) present in areas of high incidence of the EBV-associated cancer, Burkitt lymphoma.

METHODS

In this study, we analyze the kinetics of EBV-1 and EBV-2 infection in an asymptomatic infant cohort from Kisumu, Kenya. We also analyzed the kinetics of the antibody response against 5 EBV antigens, gp350 (IgG and IgA), VCA (IgG), EBNA-1 (IgG), EAd (IgG), and Zta (IgG).

RESULTS

We observed a high frequency of coinfection with both EBV types over time, with the only observable defect in the antibody response in infants coinfected being a significantly lower level of anti-gp350 IgA at peak response. Gp350 IgA levels were also significantly lower in coinfected infants 2.5 months postinfection and at the time of coinfection.

CONCLUSIONS

These results suggest that anti-gp350 IgA antibodies may be important for sterilizing immunity against secondary infection. These findings have implications for the development of an efficacious EBV vaccine to prevent both EBV-1 and EBV-2 infection in a population at high risk for Burkitt lymphoma.

Identification of multiple potent neutralizing and non-neutralizing antibodies against Epstein-Barr virus gp350 protein with potential for clinical application and as reagents for mapping immunodominant epitopes

Prevention of Epstein-Barr virus (EBV) infection has focused on generating neutralizing antibodies (nAbs) targeting the major envelope glycoprotein gp350/220 (gp350). In this study, we generated 23 hybridomas producing gp350-specific antibodies. We compared the candidate gp350-specific antibodies to the well-characterized nAb 72A1 by: (1) testing their ability to detect gp350 using enzyme-linked immunosorbent assay, flow cytometry, and immunoblot; (2) sequencing their heavy and light chain complementarity-determining regions (CDRs); (3) measuring the ability of each monoclonal antibody (mAb) to neutralize EBV infection in vitro; and (4) mapping the gp350 amino acids bound by the mAbs using competitive cell and linear peptide binding assays. We performed sequence analysis to identify 15 mAbs with CDR regions unique from those of murine 72A1 (m72A1). We observed antigen binding competition between biotinylated m72A1, serially diluted unlabeled gp350 nAbs (HB1, HB5, HB11, HB20), and our recently humanized 72A1, but not gp350 non-nAb (HB17) or anti-KSHV gH/gL antibody.

Evaluation of Total and IgA-Specific Antibody Targeting Epstein-Barr Virus Glycoprotein 350 and Nasopharyngeal Carcinoma Risk

Background

We previously reported that higher levels of antibody targeting Epstein-Barr virus (EBV) glycoprotein350 (gp350), an EBV vaccine candidate, were protective against nasopharyngeal carcinoma (NPC) in genetically high-risk families from Taiwan. The current study attempted to extend this association to a general population cohort.

Methods

We compared total and IgA-specific gp350 antibody levels in 35 incident NPC cases and 81 disease-free controls from the Cancer Screening Program in Taiwan (23943 individuals recruited 1991-1992). Luciferase immunoprecipitation assays quantified gp350 antibody.

Results

Total EBVgp350 antibody levels were not higher in individuals who remained disease free compared to those who developed NPC (P = .11). This lack of a protective gp350 association persisted for cases diagnosed ≥5 years (odds ratio [OR] = 1.05; P = .91) and <5 years (OR = 1.85; P = .40) after blood draw. IgA-specific gp350 antibody levels were higher in cases than controls (OR = 7.03; P = .001). This increased risk was most pronounced for cases diagnosed <5 years after blood draw (OR = 11.7; P = .004).

Conclusion

Unlike our prior findings in those with a strong family history of NPC, total gp350 antibody levels were not protective against NPC development in this general population setting.

A new era in cytomegalovirus vaccinology: considerations for rational design of next-generation vaccines to prevent congenital cytomegalovirus infection

Human cytomegalovirus (HCMV), a member of the beta-herpesvirus family, is the most common cause of congenital infection worldwide as well as an important cause of morbidity in transplant recipients and immunosuppressed individuals. An estimated 1 in 150 infants are infected with HCMV at birth, which can result in lifelong, debilitating neurologic sequelae including microcephaly, sensorineural hearing loss, and cognitive impairment. Natural maternal immunity to HCMV decreases the frequency of reinfection and reduces risk of congenital transmission but does not completely protect against neonatal disease. Thus, a vaccine to reduce the incidence and severity of infant infection is a public health priority. A variety of candidate HCMV vaccine approaches have been tried previously, including live-attenuated viruses, glycoprotein subunit formulations, viral vectors, and single/bivalent DNA plasmids, but all have failed to reach target endpoints in clinical trials. Nevertheless, there is a great deal to be learned from the successes and failures of the HCMV vaccine field (both congenital and transplant-associated), as well as from vaccine development efforts for other herpesvirus pathogens including herpes simplex virus 1 and 2, varicella zoster virus, and Epstein-Barr virus. Here, we review those successes and failures, evaluating recent cutting-edge discoveries that have shaped the HCMV vaccine field and identifying topics of critical importance for future investigation. These considerations will inform rational design and evaluation of next-generation vaccines to prevent HCMV-associated congenital infection and disease.

Early Epstein-Barr Virus Genomic Diversity and Convergence toward the B95.8 Genome in Primary Infection

Over 90% of the world's population is persistently infected with Epstein-Barr virus. While EBV does not cause disease in most individuals, it is the common cause of acute infectious mononucleosis (AIM) and has been associated with several cancers and autoimmune diseases, highlighting a need for a preventive vaccine. At present, very few primary, circulating EBV genomes have been sequenced directly from infected individuals. While low levels of diversity and low viral evolution rates have been predicted for double-stranded DNA (dsDNA) viruses, recent studies have demonstrated appreciable diversity in common dsDNA pathogens (e.g., cytomegalovirus). Here, we report 40 full-length EBV genome sequences obtained from matched oral wash and B cell fractions from a cohort of 10 AIM patients. Both intra- and interpatient diversity were observed across the length of the entire viral genome. Diversity was most pronounced in viral genes required for establishing latent infection and persistence, with appreciable levels of diversity also detected in structural genes, including envelope glycoproteins. Interestingly, intrapatient diversity declined significantly over time (P < 0.01), and this was particularly evident on comparison of viral genomes sequenced from B cell fractions in early primary infection and convalescence (P < 0.001). B cell-associated viral genomes were observed to converge, becoming nearly identical to the B95.8 reference genome over time (Spearman rank-order correlation test; r = -0.5589, P = 0.0264). The reduction in diversity was most marked in the EBV latency genes. In summary, our data suggest independent convergence of diverse viral genome sequences toward a reference-like strain within a relatively short period following primary EBV infection.IMPORTANCE Identification of viral proteins with low variability and high immunogenicity is important for the development of a protective vaccine. Knowledge of genome diversity within circulating viral populations is a key step in this process, as is the expansion of intrahost genomic variation during infection. We report full-length EBV genomes sequenced from the blood and oral wash of 10 individuals early in primary infection and during convalescence. Our data demonstrate considerable diversity within the pool of circulating EBV strains, as well as within individual patients. Overall viral diversity decreased from early to persistent infection, particularly in latently infected B cells, which serve as the viral reservoir. Reduction in B cell-associated viral genome diversity coincided with a convergence toward a reference-like EBV genotype. Greater convergence positively correlated with time after infection, suggesting that the reference-like genome is the result of selection.

Vaccine Development for Epstein-Barr Virus

Epstein-Barr virus (EBV) is the primary cause of infectious mononucleosis and is associated with several malignancies, including nasopharyngeal carcinoma, gastric carcinoma, Hodgkin lymphoma, Burkitt lymphoma, and lymphomas in immunocompromised persons, as well as multiple sclerosis. A vaccine is currently unavailable. While monomeric EBV gp350 was shown in a phase 2 trial to reduce the incidence of infectious mononucleosis, but not the rate of EBV infection, newer formulations of gp350 including multimeric forms, viruslike particles, and nanoparticles may be more effective. A vaccine that also includes additional viral glycoproteins, lytic proteins, or latency proteins might improve the effectiveness of an EBV gp350 vaccine. Clinical trials to determine if an EBV vaccine can reduce the rate of infectious mononucleosis or posttransplant lymphoproliferative disease should be performed. The former is important since infectious mononucleosis can be associated with debilitating fatigue as well as other complications, and EBV infectious mononucleosis is associated with increased rates of Hodgkin lymphoma and multiple sclerosis. A vaccine to reduce EBV posttransplant lymphoproliferative disease would be an important proof of principle to prevent an EBV-associated malignancy. Trials of an EBV vaccine to reduce the incidence of Hodgkin lymphoma, multiple sclerosis, or Burkitt lymphoma would be difficult but feasible.

Severity of Acute Infectious Mononucleosis Correlates with Cross-Reactive Influenza CD8 T-Cell Receptor Repertoires

Fifty years after the discovery of Epstein-Barr virus (EBV), it remains unclear how primary infection with this virus leads to massive CD8 T-cell expansion and acute infectious mononucleosis (AIM) in young adults. AIM can vary greatly in severity, from a mild transient influenza-like illness to a prolonged severe syndrome. We questioned whether expansion of a unique HLA-A2.01-restricted, cross-reactive CD8 T-cell response between influenza virus A-M1₅₈ (IAV-M1) and EBV BMLF1₂₈₀ (EBV-BM) could modulate the immune response to EBV and play a role in determining the severity of AIM in 32 college students. Only ex vivo total IAV-M1 and IAV-M1+EBV-BM cross-reactive tetramer⁺ frequencies directly correlated with AIM severity and were predictive of severe disease. Expansion of specific cross-reactive memory IAV-M1 T-cell receptor (TCR) Vβ repertoires correlated with levels of disease severity. There were unique profiles of qualitatively different functional responses in the cross-reactive and EBV-specific CD8 T-cell responses in each of the three groups studied, severe-AIM patients, mild-AIM patients, and seropositive persistently EBV-infected healthy donors, that may result from differences in TCR repertoire use. IAV-M1 tetramer⁺ cells were functionally cross-reactive in short-term cultures, were associated with the highest disease severity in AIM, and displayed enhanced production of gamma interferon, a cytokine that greatly amplifies immune responses, thus frequently contributing to induction of immunopathology. Altogether, these data link heterologous immunity via CD8 T-cell cross-reactivity to CD8 T-cell repertoire selection, function, and resultant disease severity in a common and important human infection. In particular, it highlights for the first time a direct link between the TCR repertoire with pathogenesis and the diversity of outcomes upon pathogen encounter.

The pathogenic impact of immune responses that by chance cross-react to unrelated viruses has not been established in human infections. Here, we demonstrate that the severity of acute infectious mononucleosis (AIM), an Epstein-Barr virus (EBV)-induced disease prevalent in young adults but not children, is associated with increased frequencies of T cells cross-reactive to EBV and the commonly acquired influenza A virus (IAV). The T-cell receptor (TCR) repertoire and functions of these cross-reactive T cells differed between mild- and severe-AIM patients, most likely because these two groups of patients had selected different memory TCR repertoires in response to IAV infections encountered earlier. This heterologous immunity may explain variability in disease outcome and why young adults with more-developed IAV-specific memory T-cell pools have more-severe disease than children, who have less-developed memory pools. This study provides a new framework for understanding the role of heterologous immunity in human health and disease and highlights an important developing field examining the role of T-cell repertoires in the mediation of immunopathology.