The Epstein-Barr virus (EBV)-encoded EBNA1 protein is expressed in all virus-associated tumors where it plays an essential role in the maintenance, replication and transcription of the EBV genome. Transcriptional profiling of EBNA1-expressing carcinoma cells demonstrated that EBNA1 also influences the expression of a range of cellular genes including those involved in translation, transcription and cell signaling. Of particular interest was the ability of EBNA1 to enhance expression of STAT1 and sensitize cells to interferon-induced STAT1 activation with resultant enhancement of major histocompatibility complex expression. A negative effect of EBNA1 on the expression of TGFbeta1-responsive betaig-h3 and PAI-1 genes was confirmed at the protein level in EBV-infected carcinoma cells. This effect resulted from the ability of EBNA1 to repress TGFbeta1-induced transcription via a reduction in the interaction of SMAD2 with SMAD4. More detailed analysis revealed that EBNA1 induces a lower steady-state level of SMAD2 protein as a consequence of increased protein turnover. These data show that EBNA1 can influence cellular gene transcription resulting in effects that may contribute to the development of EBV-associated tumors.

Miller-Fisher syndrome is an autoimmune neuropathy characterized by ataxia, areflexia and ophthalmoplegia, and in the majority of cases the presence of high titres of anti-GQ1b ganglioside antibodies. In an ex vivo model, human and mouse anti-GQ1b antibodies have been shown previously to induce a complement-dependent alpha-latrotoxin-like effect on the murine motor endplate, i.e. they bring about massive quantal release of acetylcholine and eventually block neuromuscular transmission. Using immunofluorescence microscopy with image analysis, we show here that the late stages of this electrophysiological effect temporally coincide with the loss of heavy neurofilament (200 kDa) and type III beta-tubulin immunostaining and structural breakdown of the nerve terminal, as demonstrated by electron microscopy. Ultrastructurally, axon terminals were disorganized, depleted of vesicles, and subdivided by the infiltrating processes of capping Schwann cells. These findings provide clear pathological evidence to support a role for anti-ganglioside antibodies in mediating nerve terminal injury and further advance the view that this site may be of importance as a target in some human neuropathies.

Epstein-Barr virus (EBV)-associated malignancies display distinct patterns of virus latent gene expression that reflect the complex interplay between the virus and its host cell. In the EBV-associated epithelial tumor nasopharyngeal carcinoma (NPC), the virusencoded latent membrane protein LMP2A is consistently expressed whereas the oncogenic LMP1 protein appears to be restricted to only a proportion of tumors. In an attempt to understand the contribution of LMP2A to the pathogenesis of NPC, we established carcinoma cell lines stably infected in vitro with either a wild-type recombinant EBV (rEBV) or a mutant rEBV in which LMP2A is deleted (rEBV-2A). An NPC-like pattern of EBV gene expression including LMP2A but not LMP1 was consistently observed in carcinoma cells infected with rEBV. However, carcinoma cells infected with rEBV-2A expressed high levels of LMP1 from the signal transducer and activator of transcription (STAT)-regulated L1-TR promoter. Consistent with this effect, basal STAT activity was reduced in rEBV-infected carcinoma cells, and this repression was relieved in the absence of LMP2A. This modulation of STAT activity correlated with the ability of LMP2A to inhibit the autocrine secretion of IL-6 from carcinoma cell lines. Exogenous IL-6 was able to induce expression of LMP1 by means of STAT3 activation both in rEBV-infected carcinoma cell lines and in the EBV-positive C666-1 NPC cell line. The LMP2A-mediated suppression of IL-6 was a consequence of NF-B inhibition. These data reveal that LMP2A modulates two key transcription factor pathways in carcinoma cells and suggest that this finding may be important in the pathogenesis of EBV-associated tumors. E pstein-Barr virus (EBV) is a ubiquitous human herpesvirus associated with the development of both lymphoid and epithelial tumors (1). The pattern of EBV latent protein expression in these tumors is different from that observed in EBVtransformed lymphoblastoid cell lines (LCLs) (2-4). Thus, only EBV-encoded nuclear antigen 1 (EBNA1) is expressed in Burkitt's lymphoma whereas EBNA1 and two membrane proteins (LMP1 and LMP2A͞B) are expressed in Hodgkin's lymphoma (HL) and nasopharyngeal carcinoma (NPC) (2, 4). The Qp promoter is responsible for specifically regulating EBNA1 expression in these tumors rather than the Cp promoter, which drives expression of all of the EBNAs in LCLs (2, 5). Likewise, in NPC and HL the expression of LMP1 is predominantly regulated by the L1-TR promoter rather than the EBNA2-responsive ED-L1 promoter used to drive LMP1 expression in B cells (6). Interestingly, the Qp, L1-TR, and ED-L1 promoters are positively regulated by the Janus kinase͞signal transducer and activator of transcription (STAT) pathway (6, 7). Although the expression of the oncogenic LMP1 protein is a consistent feature of virus-associated HL, this is not the case in NPC, where expression is variable with only Ϸ20% of biopsies being unequivocally positive for LMP1 at the protein level (8). The mechanisms underlying differential LMP1 expression in NPC and the ...