Roles of the TRAF2/3 binding site in differential B cell signaling by CD40 and its viral oncogenic mimic, LMP1

TNF Receptor Associated Factor 2 (TRAF2) Signaling in Cancer

Simple Summary

Tumor necrosis factor (TNF) receptor associated factor-2 (TRAF2) is an intracellular adapter protein with E3 ligase activity, which interacts with a plethora of other signaling proteins, including plasma membrane receptors, kinases, phosphatases, other E3 ligases, and deubiquitinases. TRAF2 is involved in various cancer-relevant cellular processes, such as the activation of transcription factors of the NFκB family, stimulation of mitogen-activated protein (MAP) kinase cascades, endoplasmic reticulum (ER) stress signaling, autophagy, and the control of cell death programs. In a context-dependent manner, TRAF2 promotes tumor development but it can also act as a tumor suppressor. Based on a general description, how TRAF2 in concert with TRAF2-interacting proteins and other TRAF proteins act at the molecular level is discussed for its importance for tumor development and its potential usefulness as a therapeutic target in cancer therapy.

Abstract

Tumor necrosis factor (TNF) receptor associated factor-2 (TRAF2) has been originally identified as a protein interacting with TNF receptor 2 (TNFR2) but also binds to several other receptors of the TNF receptor superfamily (TNFRSF). TRAF2, often in concert with other members of the TRAF protein family, is involved in the activation of the classical NFκB pathway and the stimulation of various mitogen-activated protein (MAP) kinase cascades by TNFRSF receptors (TNFRs), but is also required to inhibit the alternative NFκB pathway. TRAF2 has also been implicated in endoplasmic reticulum (ER) stress signaling, the regulation of autophagy, and the control of cell death programs. TRAF2 fulfills its functions by acting as a scaffold, bringing together the E3 ligase cellular inhibitor of apoptosis-1 (cIAP1) and cIAP2 with their substrates and various regulatory proteins, e.g., deubiquitinases. Furthermore, TRAF2 can act as an E3 ligase by help of its N-terminal really interesting new gene (RING) domain. The finding that TRAF2 (but also several other members of the TRAF family) interacts with the latent membrane protein 1 (LMP1) oncogene of the Epstein–Barr virus (EBV) indicated early on that TRAF2 could play a role in the oncogenesis of B-cell malignancies and EBV-associated non-keratinizing nasopharyngeal carcinoma (NPC). TRAF2 can also act as an oncogene in solid tumors, e.g., in colon cancer by promoting Wnt/β-catenin signaling. Moreover, tumor cell-expressed TRAF2 has been identified as a major factor-limiting cancer cell killing by cytotoxic T-cells after immune checkpoint blockade. However, TRAF2 can also be context-dependent as a tumor suppressor, presumably by virtue of its inhibitory effect on the alternative NFκB pathway. For example, inactivating mutations of TRAF2 have been associated with tumor development, e.g., in multiple myeloma and mantle cell lymphoma. In this review, we summarize the various TRAF2-related signaling pathways and their relevance for the oncogenic and tumor suppressive activities of TRAF2. Particularly, we discuss currently emerging concepts to target TRAF2 for therapeutic purposes.

Epstein-Barr Functional Mimicry: Pathogenicity of Oncogenic Latent Membrane Protein-1 in Systemic Lupus Erythematosus and Autoimmunity

Systemic lupus erythematosus (SLE) and other autoimmune diseases are propelled by immune dysregulation and pathogenic, disease-specific autoantibodies. Autoimmunity against the lupus autoantigen Sm is associated with cross-reactivity to Epstein-Barr virus (EBV) nuclear antigen 1 (EBNA-1). Additionally, EBV latent membrane protein-1 (LMP1), initially noted for its oncogenic activity, is an aberrantly active functional mimic of the B cell co-stimulatory molecule CD40. Mice expressing a transgene (Tg) for the mCD40-LMP1 hybrid molecule (containing the cytoplasmic tail of LMP1) have mild autoantibody production and other features of immune dysregulation by 2-3 months of age, but no overt autoimmune disease. This study evaluates whether exposure to the EBV molecular mimic, EBNA-1, stimulates antigen-specific and concurrently-reactive humoral and cellular immunity, as well as lupus-like features. After immunization with EBNA-1, mCD40-LMP1 Tg mice exhibited enhanced, antigen-specific, cellular and humoral responses compared to immunized WT congenic mice. EBNA-1 specific proliferative and inflammatory cytokine responses, including IL-17 and IFN-γ, were significantly increased (p<0.0001) in mCD40-LMP1 Tg mice, as well as antibody responses to amino- and carboxy-domains of EBNA-1. Of particular interest was the ability of mCD40-LMP1 to drive EBNA-1 associated molecular mimicry with the lupus-associated autoantigen, Sm. EBNA-1 immunized mCD40-LMP1 Tg mice exhibited enhanced proliferative and cytokine cellular responses (p<0.0001) to the EBNA-1 homologous epitope PPPGRRP and the Sm B/B' cross-reactive sequence PPPGMRPP. When immunized with the SLE autoantigen Sm, mCD40-LMP1 Tg mice again exhibited enhanced cellular and humoral immune responses to both Sm and EBNA-1. Cellular immune dysregulation with EBNA-1 immunization in mCD40-LMP1 Tg mice was accompanied by enhanced splenomegaly, increased serum blood urea nitrogen (BUN) and creatinine levels, and elevated anti-dsDNA and antinuclear antibody (ANA) levels (p<0.0001 compared to mCD40 WT mice). However, no evidence of immune-complex glomerulonephritis pathology was noted, suggesting that a combination of EBV and genetic factors may be required to drive lupus-associated renal disease. These data support that the expression of LMP1 in the context of EBNA-1 may interact to increase immune dysregulation that leads to pathogenic, autoantigen-specific lupus inflammation.

Role of Specific B-Cell Receptor Antigens in Lymphomagenesis

The B-cell receptor (BCR) signaling pathway is a crucial pathway of B cells, both for their survival and for antigen-mediated activation, proliferation and differentiation. Its activation is also critical for the genesis of many lymphoma types. BCR-mediated lymphoma proliferation may be caused by activating BCR-pathway mutations and/or by active or tonic stimulation of the BCR. BCRs of lymphomas have frequently been described as polyreactive. In this review, the role of specific target antigens of the BCRs of lymphomas is highlighted. These antigens have been found to be restricted to specific lymphoma entities. The antigens can be of infectious origin, such as H. pylori in gastric MALT lymphoma or RpoC of M. catarrhalis in nodular lymphocyte predominant Hodgkin lymphoma, or they are autoantigens. Examples of such autoantigens are the BCR itself in chronic lymphocytic leukemia, LRPAP1 in mantle cell lymphoma, hyper-N-glycosylated SAMD14/neurabin-I in primary central nervous system lymphoma, hypo-phosphorylated ARS2 in diffuse large B-cell lymphoma, and hyper-phosphorylated SLP2, sumoylated HSP90 or saposin C in plasma cell dyscrasia. Notably, atypical posttranslational modifications are often responsible for the immunogenicity of many autoantigens. Possible therapeutic approaches evolving from these specific antigens are discussed.

Whole-genome sequencing of Tarim red deer (Cervus elaphus yarkandensis) reveals demographic history and adaptations to an arid-desert environment

Background

The initiation of desert conditions in the Tarim Basin in China since the late Miocene has led to the significant genetic structuring of local organisms. Tarim Red Deer (Cervus elaphus yarkandensis, TRD) have adapted to the harsh environmental conditions in this basin, including high solar radiation and temperature, aridity, and poor nutritional conditions. However, the underlying genetic basis of this adaptation is poorly understood.

Results

We sequenced the whole genomes of 13 TRD individuals, conducted comparative genomic analyses, and estimated demographic fluctuation. The ∂a∂i model estimated that the TRD and Tule elk (Cervus canadensis nannodes) populations diverged approximately 0.98 Mya. Analyses revealed a substantial influence of the Earth’s climate on the effective population size of TRD, associated with glacial advances and retreat, and human activities likely underlie a recent serious decline in population. A marked bottleneck may have profoundly affected the genetic diversity of TRD populations. We detected a set of candidate genes, pathways, and GO categories related to oxidative stress, water reabsorption, immune regulation, energy metabolism, eye protection, heat stress, respiratory system adaptation, prevention of high blood pressure, and DNA damage and repair that may directly or indirectly be involved in the adaptation of TRD to an arid-desert environment.

Conclusions

Our analyses highlight the role of historical global climates in the population dynamics of TRD. In light of ongoing global warming and the increasing incidence of droughts, our study offers insights into the genomic adaptations of animals, especially TRD, to extreme arid-desert environments and provides a valuable resource for future research on conservation design and biological adaptations to environmental change.

The interactome of EBV LMP1 evaluated by proximity-based BioID approach

Epstein-Barr virus LMP1 is an oncoprotein required for immortalizing B lymphocytes and also plays important roles in transforming non-lymphoid tissue. The discovery of LMP1 protein interactions will likely generate targets to treat EBV-associated cancers. Here, we define the broader LMP1 interactome using the recently developed BioID method. Combined with mass spectrometry, we identified over 1000 proteins across seven independent experiments with direct or indirect relationships to LMP1. Pathway analysis suggests that a significant number of the proteins identified are involved in signal transduction and protein or vesicle trafficking. Interestingly, a large number of proteins thought to be important in the formation of exosomes and protein targeting were recognized as probable LMP1 interacting partners, including CD63, syntenin-1, ALIX, TSG101, HRS, CHMPs, and sorting nexins. Therefore, it is likely that LMP1 modifies protein trafficking and exosome biogenesis pathways. In support of this, knock-down of syntenin-1 and ALIX resulted in reduced exosomal LMP1.

The oncogenic membrane protein LMP1 sequesters TRAF3 in B-cell lymphoma cells to produce functional TRAF3 deficiency

Loss-of-function mutations in genes encoding the signaling protein tumor necrosis factor receptor-associated factor 3 (TRAF3) are commonly found in human B-cell malignancies, especially multiple myeloma and B-cell lymphoma (BCL). B-cell TRAF3 deficiency results in enhanced cell survival, elevated activation receptor signaling, and increased activity of certain transcriptional pathways regulating expression of prosurvival proteins. A recent analysis of TRAF3 protein staining of ∼300 human BCL tissue samples revealed that a higher proportion of samples expressing the oncogenic Epstein-Barr virus-encoded protein latent membrane protein 1 (LMP1) showed low/negative TRAF3 staining than predicted. LMP1, a dysregulated mimic of the CD40 receptor, binds TRAF3 more effectively than CD40. We hypothesized that LMP1 may sequester TRAF3, reducing its availability to inhibit prosurvival signaling pathways in the B cell. This hypothesis was addressed via 2 complementary approaches: (1) comparison of TRAF3-regulated activation and survival-related events with relative LMP1 expression in human BCL lines and (2) analysis of the impact upon such events in matched pairs of mouse BCL lines, both parental cells and subclones transfected with inducible LMP1, either wild-type LMP1 or a mutant LMP1 with defective TRAF3 binding. Results from both approaches showed that LMP1-expressing B cells display a phenotype highly similar to that of B cells lacking TRAF3 genes, indicating that LMP1 can render B cells functionally TRAF3 deficient without TRAF3 gene mutations, a finding of significant relevance to selecting pathway-targeted therapies for B-cell malignancies.

Roles for TNF-receptor associated factor 3 (TRAF3) in lymphocyte functions

TRAF3 is an adapter protein that serves and regulates the functions of several types of receptors, located both inside the cell and at the plasma membrane. These include members of the TNF receptor superfamily (TNFR-SF), toll-like receptors (TLR), and cytokine receptors. It has become increasingly evident that the roles and functions of TRAF3 are highly context-dependent. TRAF3 can serve distinct roles for different receptors in the same cell, and also has highly cell-type-dependent functions. This review focuses upon the current state of knowledge regarding how TRAF3 regulates the biology and effector functions of B and T lymphocytes, two major cell types of the adaptive immune response in which TRAF3 has markedly distinct roles.

TRAF6 is a critical regulator of LMP1 functions in vivo

EBV-encoded latent membrane protein 1 (LMP1) is critical for EBV-driven B-cell transformation and most EBV-associated malignancies and is also implicated in exacerbation of autoimmunity. LMP1 functionally mimics the TNFR superfamily member CD40, but LMP1-induced signals and downstream B-cell functions are amplified and sustained compared with those mediated by CD40. CD40 and LMP1 both depend upon TNFR-associated factor (TRAF) adaptor molecules to mediate signaling but use them differently. LMP1 is dependent upon TRAFs 3 and 5 to deliver B-cell activation signals, while CD40 predominantly uses TRAFs 2 and 6 for this purpose. Both LMP1 and CD40 functions in B cells require TRAF6, which physically associates with both receptors but via different binding sites. In B-cell CD40 signaling, TRAF6 is required for a particular subset of CD40-dependent immune functions in vivo. Inasmuch as CD40 and LMP1 use other TRAFs differentially, we predicted that TRAF6 is critical for a specific subset of LMP1 functions in vivo and that this subset will be overlapping but distinct from the TRAF6-requiring functions of CD40. This study tests this prediction using a B-cell-specific TRAF6-deficient mouse model. We found that B-cell TRAF6 is important for LMP1-mediated antibody and autoantibody production in mice, as well as germinal center formation, but not the secondary lymphoid organ enlargement that results from LMP1 transgenic expression. Results highlight differential TRAF6 requirements for specific B-cell functions by LMP1 versus CD40. These differences may make important contributions to the contrasts between normally regulated CD40 versus pathogenic LMP1-mediated signals.

TRAF binding is required for a distinct subset of in vivo B cell functions of the oncoprotein LMP1

EBV-encoded latent membrane protein 1 (LMP1) is important for EBV contributions to B cell transformation and many EBV-associated malignancies, as well as EBV-mediated exacerbation of autoimmunity. LMP1 functionally mimics TNF receptor (TNFR) superfamily member CD40, but LMP1 signals and downstream effects are amplified and sustained compared with CD40. CD40 and LMP1 both use TNFR-associated factor (TRAF) adaptor proteins, but in distinct ways. LMP1 functions require TRAFs 3, 5, and 6, which interact with LMP1. However, TRAFs can also contribute to signaling in the absence of direct interactions with cell surface receptors, so we investigated whether their roles in LMP1 in vivo functions require direct association. We show in this study that the LMP1 TRAF binding site was required for LMP1-mediated autoantibody production, the germinal center response to immunization, and optimal production of several isotypes of Ig, but not LMP1-dependent enlargement of secondary lymphoid organs in transgenic mice. Thus, LMP1 in vivo effects can be mediated via both TRAF binding-dependent and -independent pathways. Together with our previous findings, these results indicate that TRAF-dependent receptor functions may not always require TRAF-receptor binding. These data suggest that TRAF-mediated signaling pathways, such as those of LMP1, may be more diverse than previously appreciated. This finding has significant implications for receptor and TRAF-targeted therapies.

Roles of the kinase TAK1 in TRAF6-dependent signaling by CD40 and its oncogenic viral mimic, LMP1

The Epstein-Barr virus (EBV)-encoded protein latent membrane protein 1 (LMP1) is essential for EBV-mediated B cell transformation and plays a critical role in the development of post-transplant B cell lymphomas. LMP1 also contributes to the exacerbation of autoimmune diseases such as systemic lupus erythematosus (SLE). LMP1 is a functional mimic of the tumor necrosis factor receptor (TNFR) superfamily member CD40, and relies on TNFR-associated factor (TRAF) adaptor proteins to mediate signaling. However, LMP1 activation signals to the B cell are amplified and sustained compared to CD40 signals. We previously demonstrated that LMP1 and CD40 use TRAF molecules differently. Although associating with CD40 and LMP1 via separate mechanisms, TRAF6 plays a significant role in signal transduction by both. It is unknown whether TRAF6 mediates CD40 versus LMP1 functions via distinct or shared pathways. In this study, we tested the hypothesis that TRAF6 uses the kinase TAK1 to trigger important signaling pathways following both CD40 and LMP1 stimulation. We determined that TAK1 was required for JNK activation and interleukin-6 (IL-6) production mediated by CD40 and LMP1, in both mouse and human B cells. Additionally, TRAF3 negatively regulated TRAF6-dependent, CD40-mediated TAK1 activation by limiting TRAF6 recruitment. This mode of regulation was not observed for LMP1 and may contribute to the dysregulation of LMP1 compared to CD40 signals.

Roles of tumor necrosis factor receptor associated factor 3 (TRAF3) and TRAF5 in immune cell functions

A large and diverse group of receptors utilizes the family of cytoplasmic signaling proteins known as tumor necrosis factor receptor (TNFR)-associated factors (TRAFs). In recent years, there has been a resurgence of interest and exploration of the roles played by TRAF3 and TRAF5 in cellular regulation, particularly in cells of the immune system, the cell types of focus in this review. This work has revealed that TRAF3 and TRAF5 can play diverse roles for different receptors even in the same cell type, as well as distinct roles in different cell types. Evidence indicates that TRAF3 and TRAF5 play important roles beyond the TNFR-superfamily (SF) and viral mimics of its members, mediating certain innate immune receptor and cytokine receptor signals, and most recently, signals delivered by the T-cell receptor (TCR) signaling complex. Additionally, much research has demonstrated the importance of TRAF3-mediated cellular regulation via its cytoplasmic interactions with additional signaling proteins. In particular, we discuss below evidence for the participation by TRAF3 in a number of the regulatory post-translational modifications involving ubiquitin that are important in various signaling pathways.

Differential expression of the adaptor protein HSH2 controls the quantitative and qualitative nature of the humoral response

Endogenous expression of the adaptor protein hematopoietic Src homology 2-containing adaptor protein (HSH2) is regulated in a dynamic manner during B cell maturation and differentiation. Developing B cells lack detectable HSH2, whereas transitional 1 and 2 B cells in the periphery exhibit increasing levels of expression. Mature follicular B cells exhibit decreased expression of HSH2 compared with transitional 2 B cells, and expression is further downregulated in germinal center B cells. In contrast, marginal zone B cells and B1a/b B cells exhibit high-level HSH2 expression. Regulation of HSH2 expression plays a critical role in determining the outcome of the humoral immune response as demonstrated using HSH2 transgenic (Tg) mice. Constitutive expression of HSH2 in the B lineage at levels comparable to B1a/b B cells results in decreased serum Ig titers for all subclasses with the exception of IgA. HSH2 Tg mice immunized with T-dependent or T-independent Ags exhibit a moderate decrease in the production of Ag-specific IgM, whereas class-switched isotypes are decreased by ∼80-90% compared with control mice. Analysis of HSH2 Tg B cell activation in vitro demonstrated that HSH2 selectively regulates the B cell response to TNF family receptors (i.e., CD40 and BAFF-R), but not BCR- or TLR-dependent signals. These data demonstrate that changes in HSH2 expression have profound effects on the humoral immune response.

Molecular mechanisms of TNFR-associated factor 6 (TRAF6) utilization by the oncogenic viral mimic of CD40, latent membrane protein 1 (LMP1)

Latent membrane protein 1 (LMP1), encoded by Epstein-Barr virus, is required for EBV-mediated B cell transformation and plays a significant role in the development of posttransplant B cell lymphomas. LMP1 has also been implicated in exacerbation of autoimmune diseases such as systemic lupus erythematosus. LMP1 is a constitutively active functional mimic of the tumor necrosis factor receptor superfamily member CD40, utilizing tumor necrosis factor receptor-associated factor (TRAF) adaptor proteins to induce signaling. However, LMP1-mediated B cell activation is amplified and sustained compared with CD40. We have previously shown that LMP1 and CD40 use TRAFs 1, 2, 3, and 5 differently. TRAF6 is important for CD40 signaling, but the role of TRAF6 in LMP1 signaling in B cells is not clear. Although TRAF6 binds directly to CD40, TRAF6 interaction with LMP1 in B cells has not been characterized. Here we tested the hypothesis that TRAF6 is a critical regulator of LMP1 signaling in B cells, either as part of a receptor-associated complex and/or as a cytoplasmic adaptor protein. Using TRAF6-deficient B cells, we determined that TRAF6 was critical for LMP1-mediated B cell activation. Although CD40-mediated TRAF6-dependent signaling does not require the TRAF6 receptor-binding domain, we found that LMP1 signaling required the presence of this domain. Furthermore, TRAF6 was recruited to the LMP1 signaling complex via the TRAF1/2/3/5 binding site within the cytoplasmic domain of LMP1.

Differential B-lymphocyte regulation by CD40 and its viral mimic, latent membrane protein 1

CD40 plays a vital role in humoral immunity, via its potent and multifaceted function as an activating receptor of various immune cells, most notably B lymphocytes. The Epstein-Barr virus-encoded transforming protein latent membrane protein 1 (LMP1) serves as a functional mimic of CD40 signals to B cells but lacks key regulatory controls that restrain CD40 signaling. This allows LMP1 to activate B cells in an abnormal manner that can contribute to the pathogenesis of human B-cell lymphoma and autoimmune disease. This review focuses upon a comparative analysis of CD40 versus LMP1 functions and mechanisms of action in B lymphocytes, discussing how this comparison can provide valuable information on both how CD40 signaling is normally regulated and how LMP1 disrupts the normal CD40 pathways, which can provide information of value to therapeutic design.

Concept and application of a computational vaccinology workflow

BACKGROUND

The last years have seen a renaissance of the vaccine area, driven by clinical needs in infectious diseases but also chronic diseases such as cancer and autoimmune disorders. Equally important are technological improvements involving nano-scale delivery platforms as well as third generation adjuvants. In parallel immunoinformatics routines have reached essential maturity for supporting central aspects in vaccinology going beyond prediction of antigenic determinants. On this basis computational vaccinology has emerged as a discipline aimed at ab-initio rational vaccine design.Here we present a computational workflow for implementing computational vaccinology covering aspects from vaccine target identification to functional characterization and epitope selection supported by a Systems Biology assessment of central aspects in host-pathogen interaction. We exemplify the procedures for Epstein Barr Virus (EBV), a clinically relevant pathogen causing chronic infection and suspected of triggering malignancies and autoimmune disorders.

RESULTS

We introduce pBone/pView as a computational workflow supporting design and execution of immunoinformatics workflow modules, additionally involving aspects of results visualization, knowledge sharing and re-use. Specific elements of the workflow involve identification of vaccine targets in the realm of a Systems Biology assessment of host-pathogen interaction for identifying functionally relevant targets, as well as various methodologies for delineating B- and T-cell epitopes with particular emphasis on broad coverage of viral isolates as well as MHC alleles.Applying the workflow on EBV specifically proposes sequences from the viral proteins LMP2, EBNA2 and BALF4 as vaccine targets holding specific B- and T-cell epitopes promising broad strain and allele coverage.

CONCLUSION

Based on advancements in the experimental assessment of genomes, transcriptomes and proteomes for both, pathogen and (human) host, the fundaments for rational design of vaccines have been laid out. In parallel, immunoinformatics modules have been designed and successfully applied for supporting specific aspects in vaccine design. Joining these advancements, further complemented by novel vaccine formulation and delivery aspects, have paved the way for implementing computational vaccinology for rational vaccine design tackling presently unmet vaccine challenges.

Differential TRAF3 utilization by a variant human CD40 receptor with enhanced signaling

CD40 is required for T cell-dependent humoral immunity, but it can also contribute to the pathogenesis of autoimmunity and B cell malignancy. The TNFR-associated factor (TRAF)2 and TRAF6 adaptor proteins are positive regulators of CD40 signaling required to activate downstream kinase cascades and transcription factors. In contrast, TRAF3 can serve as a negative regulator of CD40 signaling, and CD40 signals are amplified in TRAF3(-/-) B cells. We previously reported a gain-of-function polymorphism of the human CD40 receptor, hCD40-P227A, which signals in an amplified manner to B lymphocytes. In this study, we show that hCD40-P227A binds more TRAF3 and TRAF5, as well as certain associated proteins, than wild-type-CD40. Studies in TRAF-deficient B cell lines revealed that hCD40-P227A uses TRAF3 as a positive rather than negative regulator. Although located outside of any known TRAF binding sites, the P227A polymorphism can alter TRAF binding and dramatically changes the role played by TRAF3 in CD40 signaling.

Natural killer cell lymphoma in a pediatric patient with inflammatory bowel disease

Tumor necrosis factor α (TNF-α) antibody agents are an effective therapy for the treatment of inflammatory bowel disease (IBD); however, because of the potential for immune suppression with these drugs, TNF-α antibody agents can increase the risk of malignancy. We report here the case of an 11-year-old boy who presented with bowel obstruction. He also had a history of periodic fever, aphthous stomatitis, and cervical adenitis (PFAPA). Intestinal inflammation continued and impaired his quality of life; he was diagnosed with IBD of an undetermined type (IBD-U). Symptoms improved with infliximab, but he developed elevated transaminase levels with hepatosplenomegaly 1 year after scheduled infusions. Skin biopsy revealed an atypical lymphoid infiltrate consistent with an Epstein-Barr virus (EBV)-positive natural killer (NK)/T-cell lymphoma with associated hemophagocytic lymphohistiocytosis. Bone marrow biopsy revealed a similar EBV-positive lymphoid infiltrate consistent with an NK/T-cell lymphoma. EBV-positive tissue was present in gastrointestinal biopsies. Flow-cytometric analysis revealed an atypical, clonal NK-cell population, and biopsy specimens from several tissue sites tested positive for CD3, CD56, and CD30. The patient died soon after the diagnosis was made. This patient developed an EBV-driven malignancy while receiving infliximab. All patients with IBD who receive infliximab should be monitored for malignancy, especially young patients. This case underscores the need for future studies to better understand the biology of lymphoproliferative disorders.

Human TRAF3 adaptor molecule deficiency leads to impaired Toll-like receptor 3 response and susceptibility to herpes simplex encephalitis

Tumor necrosis factor (TNF) receptor-associated factor 3 (TRAF3) functions downstream of multiple TNF receptors and receptors that induce interferon-α (IFN-α), IFN-β, and IFN-λ production, including Toll-like receptor 3 (TLR3), which is deficient in some patients with herpes simplex virus-1 encephalitis (HSE). Mice lacking TRAF3 die in the neonatal period, preventing direct investigation of the role of TRAF3 in immune responses and host defenses in vivo. Here, we report autosomal dominant, human TRAF3 deficiency in a young adult with a history of HSE in childhood. The TRAF3 mutant allele is loss-of-expression, loss-of-function, dominant-negative and associated with impaired, but not abolished, TRAF3-dependent responses upon stimulation of both TNF receptors and receptors that induce IFN production. TRAF3 deficiency is associated with a clinical phenotype limited to HSE resulting from the impairment of TLR3-dependent induction of IFN. Thus, TLR3-mediated immunity against primary infection by HSV-1 in the central nervous system is critically dependent on TRAF3.