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Evasion of affinity-based selection in germinal centers by Epstein-Barr virus LMP2A

ABSTRACT: Abstract: Epstein-Barr virus (EBV) infects germinal center (GC) B cells and establishes persistent infection in memory B cells. EBV-infected B cells sometimes cause B cell malignancies in humans with T- or NK-cell deficiency. We now find EBV-encoded Latent Membrane Protein 2A (LMP2A) to mimic B cell antigen receptor (BCR) signaling in murine GC B cells, causing altered humoral immune responses and autoimmune diseases. Investigation of the impact of LMP2A on B cell differentiation in mice that conditionally express LMP2A in GC B cells, or all B-lineage cells, found LMP2A expression enhanced not only BCR signals but also plasma-cell differentiation, in vitro and in vivo. Conditional LMP2A expression in GC B cells resulted in preferential selection of low-affinity antibody–producing B-cells despite apparently normal GC formation. GC B cell-specific LMP2A expression led to systemic lupus erythematosus-like autoimmune phenotypes in an age-dependent manner. Epigenetic profiling of LMP2A B cells found increased H3K27ac and H3K4me1 signals at the Zbtb20 locus. We conclude that LMP2A reduces the stringency of GC B cell selection and may contribute to persistent EBV infection and pathogenesis by providing GC B cells with pro-survival signals. Significance Statement: Epstein-Barr virus (EBV) is a human herpesvirus that establishes persistent infection of the B-cell compartment. EBV is associated with autoimmune diseases, including systemic lupus erythematosus (SLE). However, the molecular mechanisms by which EBV contributes to autoimmunity remain unclear. We used transgenic mouse models to study the role of EBV-encoded Latent membrane protein 2A (LMP2A), which mimics B-cell receptor signaling.　Interestingly, LMP2A not only enhanced B-cell survival, but also upregulated the transcription factor Zbtb20 and promoted plasma cell differentiation. When expressed late in B-cell development, LMP2A also caused prominent features of SLE, including autoantibody production with kidney immune complex deposition. Our findings suggest that LMP2A has important roles in B cell activation, differentiation and the development of EBV-associated autoimmune diseases.

ORGANISM(S): Mus musculus

PROVIDER: GSE71408 | GEO | 2015/10/01

SECONDARY ACCESSION(S): PRJNA291101

REPOSITORIES: GEO

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Project description:The better prognosis of patients with Epstein-Barr virus-positive gastric carcinoma than those with EBV-negative GC is correlated with the degree of recruitment of inflammatory tumor infiltrating cells (TIL) to the vicinity of tumor cells. We hypothesized that the better prognosis would associate with less genetic or epigenetic alterations in EBV(+)GC, or EBV infection should deregulate immune modulator proteins, of which secretion recruit TIL. Therefore we performed mRNA expression profilings in EBV(-)GC and EBV(+)GC, each of which was pair wise compared with their normal control. We found that EBV(+)GC had much more molecular homogeneity with focused alterations in immune modulator genes; The Pearson correlation matrix analyses demonstrated that EBV(+)GC tumor showed remarkably high tumor homogeneity. While EBV(-)GC had considerable number genes that are differentially expressed genes from their normal counterparts, EBV(+)GC showed only a handful, almost 20 fold less number of DEG than EBV(-)GC under the same p value cutoff (p<0.001). Gene ontology and pathway analyses showed that while pathways of cation homeostasis, digestion and ion transport were commonly deregulated in both GC types, genes for chromatin assembly, prostaglandin receptor activity, pattern specification process are selectively deregulated in EBV(-)GC tumors. In contrast, pathways or genes for cytokine activity, immune response and lipoprotein particle clearance are selectively deregulated in EBV(+)GC tumors. These results demonstrate that EBV(+)GC inherently evolves to high homogeneity with fewer changes in gene expression and these secret immune modulatory chemokines could recruit reactive immune cells to EBV(+)GC, leading to favorable microenvironment for cancer suppression. All patients underwent the surgery for advanced gastric carcinoma (GC) except one patient with early GC. The EBV-presence in the GC was verified by in situ EBV-encoded small RNA (ERER) staining.. The 14 paired EBV(-)GC patients and 12 paired EBV(+)GC patients were selected for this study. Tumor tissue (T)and normal tissues (N) from distant sites from tumor areas were dissected, frozen at -80C and were subjected to RNA purification, mRNA array profiling analyses.

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Evasion of affinity-based selection in germinal centers by Epstein-Barr virus LMP2A

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