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A significant percentage of the population is latently infected with Epstein-Barr virus (EBV). In most individuals, no clinical symptoms are evident. However, in a subset of individuals with compromised immune systems, EBV infection is associated with lymphomas, such as Burkitt's and non-Hodgkin's lymphomas (34, 47). Furthermore, approximately 40% of Hodgkin's lymphoma cases are positive for EBV latent infection, suggesting that there is a causal relationship between EBV infection and the occurrence of Hodgkin's lymphoma (31, 32). Most recently, our laboratory has implicated that an EBVencoded protein, latent membrane protein 2A (LMP2A), alters gene expression in a manner similar to that observed in Hodgkin Reed-Sternberg cells. These data indicate that LMP2A may play a role in the development of Hodgkin's lymphoma (46). In addition, LMP2A expression is readily detected in vivo, suggesting that LMP2A plays a critical role in the EBV life cycle (4,5,14,26). Therefore, understanding the functions of EBV latency proteins may allow for therapeutic interventions to prevent or treat EBV latency and subsequent lymphomas.Studies using human lymphoblastoid cell lines (LCLs) demonstrate that LMP2A induces the constitutive phosphorylation of numerous signal transduction proteins utilized by the B-cell receptor (BCR) (such as Lyn, Syk, and phosphatidylinositol 3-kinase [PI3K]) (19,38,46,49). In these LCLs, LMP2A inhibits the BCR-induced activation of these proteins, suggesting that LMP2A blocks BCR signal transduction in latently infected B cells. However, LCLs are immortalized and actively dividing and express numerous EBV proteins, which is quite different from the EBV latency patterns observed in vivo (3,4,26). Thus, studies of LMP2A function in primary B cells are needed to determine how LMP2A alters normal primary BCR signaling in vivo.In humans, the B cells in which EBV resides are rare (1 in 10 5 to 10 6 B cells) (29, 41, 52), and therefore it is difficult to obtain sufficient numbers of B cells to study how EBV alters their normal function. To address this question, we produced transgenic (Tg) mice that express LMP2A in developing B cells (TgE-Tg) (10, 11). These mice produced immunoglobulin M (IgM)-negative B cells that survive and colonize peripheral organs (11,27). It was proposed that LMP2A acted similarly to a pre-BCR during development since LMP2A decreased the expression of proteins important for rearranging the IgM heavy chain (45) and subsequent heavy-chain rearrangement (11). The survival of these IgM-negative B cells further suggested that LMP2A acted as a BCR mimic, since B cells normally undergo apoptosis from a lack of a tonic BCR-derived survival signal (30, 33). More recently, findings from our laboratory have suggested that LMP2A protects B cells from apoptosis by the RAS/PI3K/AKT pathway (19,46). This model revealed a novel function for LMP2A whereby this latently expressed EBV protein provides a surrogate BCR-like stimulus to promote B-cell development and peripheral B-cell survival. Despite the d...

Despite the identification of Epstein-Barr virus (EBV) in tumors of Burkitt's lymphoma (BL) over 40 years ago, the exact contribution of EBV to BL is undefined. EBV encodes for multiple proteins in latent B cells that affect B cell survival and activation. One such protein, latent membrane protein 2A (LMP2A), protects B cells from numerous pro-apoptotic stimuli. Therefore, we tested whether LMP2A protects B cells from apoptosis induced by aberrant c-MYC expression that precedes and dominates BL. We crossed LMP2A-transgenic mice (LMP2A-Tg), in which all B cells express LMP2A, to a transgenic mouse that expresses a BL translocation of myc (k-MYC-Tg mice). LMP2A promotes proliferation and protects B cells from MYC-induced apoptosis in k-MYC-Tg mice. LMP2A also accelerates the development of lymphoma in LMP2A/k-MYC-Tg mice. Finally, LMP2A increases the expression of Bcl-X L in both pretumor B cells and tumor cells, suggesting a mechanism for LMP2A-mediated B cell survival in the presence of MYC. These results support a hypothesis that EBV LMP2A promotes tumor development by protecting pre-tumor B cells that would normally apoptose after the c-myc translocation.

The COVID-19 pandemic caused by SARS-CoV-2 is in immediate need of an effective antidote. Although the Spike glycoprotein (SgP) of SARS-CoV-2 has been shown to bind to heparins, the structural features of this interaction, the role of a plausible heparan sulfate proteoglycan (HSPG) receptor, and the antagonism of this pathway through small molecules remain unaddressed. Using an in vitro cellular assay, we demonstrate HSPGs modified by the 3-O-sulfotransferase isoform-3, but not isoform-5, preferentially increased SgP-mediated cell-to-cell fusion in comparison to control, unmodified, wild-type HSPGs. Computational studies support preferential recognition of the receptor-binding domain of SgP by 3-O-sulfated HS sequences. Competition with either fondaparinux, a 3-O-sulfated HS-binding oligopeptide, or a synthetic, non-sugar small molecule, blocked SgP-mediated cell-to-cell fusion. Finally, the synthetic, sulfated molecule inhibited fusion of GFP-tagged pseudo SARS-CoV-2 with human 293T cells with sub-micromolar potency. Overall, overexpression of 3-O-sulfated HSPGs contribute to fusion of SARS-CoV-2, which could be effectively antagonized by a synthetic, small molecule.

Epstein-Barr virus (EBV) latently infected B-cells are the precursors of EBV-associated malignancies. EBV-infection induces the production of pro-survival and anti-inflammatory cytokines that may be important in the transition between latency and malignancy. One EBV protein, LMP2A, can be detected in both latently infected resting B-cells and in EBV-associated malignancies. Therefore, we tested the ability of LMP2A to influence cytokine production using both LMP2A-Tg primary B-cells and LMP2A-expressing B-cell lines. Our data demonstrate that LMP2A does not globally alter B-cell-produced cytokine levels, but specifically targets IL-10. Additional studies using ELISA and real-time-RT-PCR confirm that LMP2A utilizes PI3-kinase to increase IL-10 levels. Finally, the data demonstrate that LMP2A-expressing B-cell lines are more dependent on IL-10 for survival in comparison to LMP2A-negative B-cell lines. These data identify a novel function of LMP2A in the alteration of a cytokine that is important for both tumour survival and anti-tumour responses.