Human B cells are the primary targets of Epstein–Barr virus (EBV) infection. In most cases, EBV infection is asymptomatic because of a highly effective host immune response, but some individuals develop self-limiting infectious mononucleosis, while others develop EBV-associated lymphoid or epithelial malignancies. The viral and immune factors that determine the outcome of infection are not understood. The EBV life cycle includes a lytic phase, culminating in the production of new viral particles, and a latent phase, during which the virus remains largely silent for the lifetime of the host in memory B cells. Thus, in healthy individuals, there is a tightly orchestrated interplay between EBV and the host that allows the virus to persist. To promote viral persistence, EBV has evolved a variety of strategies to modulate the host immune response including inhibition of immune cell function, blunting of apoptotic pathways, and interfering with antigen processing and presentation pathways. In this article, we focus on mechanisms by which dysregulation of the host B cell and immune modulation by the virus can contribute to development of EBV+ B cell lymphomas.

Regulatory B cells (Bregs) suppress immune responses through the secretion of interleukin-10 (IL-10). This immunomodulatory capacity holds therapeutic potential, yet a definitional immunophenotype for enumeration and prospective isolation of B cells capable of IL-10 production remains elusive. Here, we simultaneously quantify cytokine production and immunophenotype in human peripheral B cells across a range of stimulatory conditions and time points using mass cytometry. Our analysis shows that multiple functional B cell subsets produce IL-10 and that no phenotype uniquely identifies IL-10⁺ B cells. Further, a significant portion of IL-10⁺ B cells co-express the pro-inflammatory cytokines IL-6 and tumor necrosis factor alpha (TNFα). Despite this heterogeneity, operationally tolerant liver transplant recipients have a unique enrichment of IL-10⁺, but not TNFα⁺ or IL-6⁺, B cells compared with transplant recipients receiving immunosuppression. Thus, human IL-10-producing B cells constitute an induced, transient state arising from a diversity of B cell subsets that may contribute to maintenance of immune homeostasis.

Systemic lupus erythematosus (SLE) is a systemic autoimmune disease characterized by antinuclear antibodies (ANAs). Epstein-Barr virus (EBV) infection has been epidemiologically associated with SLE, yet its role in pathogenesis remains incompletely defined. Here, we developed an EBV-specific single-cell RNA-sequencing platform and used it to demonstrate that EBV infection reprograms autoreactive antinuclear antigen B cells to drive autoimmunity in SLE. We demonstrated that, in SLE, EBV ⁺ B cells are predominantly CD27 ⁺ CD21 ^low memory B cells that are present at increased frequencies and express ZEB2 , TBX21 (T-bet), and antigen-presenting cell transcriptional pathways. Integrative analysis of chromatin immunoprecipitation sequencing (ChIP-seq), assay for transposase-accessible chromatin sequencing (ATAC-seq), and RNA polymerase II occupancy data revealed EBV nuclear antigen 2 (EBNA2) binding at the transcriptional start sites and regulatory regions of CD27 , ZEB2 , and TBX21 , as well as the antigen-presenting cell genes demonstrated to be up-regulated in SLE EBV ⁺ B cells. We expressed recombinant antibodies from SLE EBV ⁺ B cells and demonstrated that they bind prototypical SLE nuclear autoantigens, whereas those from healthy individuals do not. We further found that SLE EBV ⁺ B cells can serve as antigen-presenting cells to drive activation of T peripheral helper cells with concomitant activation of related EBV ⁻ antinuclear double-negative 2 B cells and plasmablasts. Our results provide a mechanistic basis for EBV being a driver of SLE through infecting and reprogramming nuclear antigen-reactive B cells to become activated antigen-presenting cells with the potential to promote systemic disease–driving autoimmune responses.

Posttransplant lymphoproliferative disorder (PTLD) is a serious complication in organ transplant recipients and is most often associated with the Epstein Barr virus (EBV). EBV is a common gammaherpes virus with tropism for B lymphocytes and infection in immunocompetent individuals is typically asymptomatic and benign. However, infection in immunocompromised or immunosuppressed individuals can result in malignant B cell lymphoproliferations, such as PTLD. EBV+ PTLD can arise after primary EBV infection, or because of reactivation of a prior infection, and represents a leading malignancy in the transplant population. The incidence of EBV+ PTLD is variable depending on the organ transplanted and whether the recipient has preexisting immunity to EBV but can be as high as 20%. It is generally accepted that impaired immune function due to immunosuppression is a primary cause of EBV+ PTLD. In this overview, we review the EBV life cycle and discuss our current understanding of the immune response to EBV in healthy, immunocompetent individuals, in transplant recipients, and in PTLD patients. We review the strategies that EBV uses to subvert and evade host immunity and discuss the implications for the development of EBV+ PTLD.

The explosion of genetic information from recent advances in sequencing technologies, bioinformatics and genomics highlights the importance of understanding mechanisms involved in gene expression and regulation. Over the last decade, it has become clear that small ribonucleic acids (RNAs) are a central component of the cellular gene regulatory network. MicroRNAs (miRNAs) are a family of endogenous, small, noncoding single‐stranded RNA of ∼22 nucleotides in length that act as posttranscriptional gene regulatory elements. MicroRNAs can inhibit de novo protein synthesis by blocking translation through base‐pairing with complementary messenger RNA (mRNA) and also suppress translation by promoting degradation of target mRNA. MicroRNAs are intimately involved in a variety of biologic processes including development, hematopoietic cell differentiation, apoptosis and proliferation. To date, over 800 human miRNAs have been identified, though the biologic function of only a fraction of miRNAs has been elucidated. Here, we discuss how miRNAs are produced, identified and quantitated, and focus on several key miRNAs that govern expression of genes relevant to allograft rejection, tolerance induction and posttransplant infection. Finally, we discuss potential ways in which the miRNA network can be modulated that ultimately may offer new strategies to promote long‐term graft survival.

Epstein-Barr virus (EBV) infection is linked to approximately 90% of B-cell lymphomas associated with posttransplant lymphoproliferative disease (PTLD), a serious complication for immunosuppressed transplant recipients. In this paper, we review the myriad ways by which EBV can inadvertently drive the genesis and persistence of B-cell lymphomas, particularly when the antiviral immune response is compromised. Probing the basic mechanisms by which EBV infection proceeds and contributes to malignancy in such cases will hopefully improve our understanding and treatment of PTLD and other EBV-associated malignancies.