Multiple sclerosis (MS) is a widespread neurodegenerative autoimmune disease with unknown etiology. It is increasingly evident that, together with pathogenic T cells, autoreactive B cells are among the major players in MS development. The analysis of myelin neuroantigen-specific antibody repertoires and their possible cross-reactivity against environmental antigens, including viral proteins, could shed light on the mechanism of MS induction and progression. A phage display library of single-chain variable fragments (scFvs) was constructed from blood lymphocytes of patients with MS as a potential source of representative MS autoantibodies. Structural alignment of 13 clones selected toward myelin basic protein (MBP), one of the major myelin antigens, showed high homology within variable regions with cerebrospinal fluid MS-associated antibodies as well as with antibodies toward Epstein-Barr latent membrane protein 1 (LMP1). Three scFv clones showed pronounced specificity to MBP fragments 65-92 and 130-156, similar to the serum MS antibodies. One of these clones, designated E2, in both scFv and full-size human antibody constructs, was shown to react with both MBP and LMP1 proteins in vitro, suggesting natural cross-reactivity. Thus, antibodies induced against LMP1 during Epstein-Barr virus infection might act as inflammatory trigger by reacting with MBP, suggesting molecular mimicry in the mechanism of MS pathogenesis.

Chronic infections caused by hepatitis B virus (HBV) and/or hepatitis C virus (HCV) are the main risk factors for the development of hepatocellular carcinoma (HCC) in humans. Both viruses cause a wide spectrum of clinical manifestations ranging from healthy carrier state to acute and chronic hepatitis, liver cirrhosis, and HCC. HBV and HCV belong to different viral families (Hepadnoviridae and Flaviviridae, respectively); they are characterized by different genetic structures. Clinical manifestations of these viral infections result from the interaction between these viruses and host hepatocytes (i.e. between viral and cell genomes). Proteins encoded by both viruses play an important role in processes responsible for immortalization and transformation of these cells. Chronic inflammation determined by host immune response to the viral infection, hepatocyte death and their compensatory proliferation, as well as modulation of expression of some regulatory proteins of the cell (growth factors, cytokines, etc.) are the processes that play the major role in liver cancer induced by HBV and HCV.

Germ cell tumors (GCT) are strictly associated with the expression of HERV-K(HML-2) proviruses, and the majority of GCT patients produce antibodies to structural proteins of these proviruses. The objective of our study was to determine the significance of the serological response to HERV-K(HML-2) Gag and Env proteins for diagnosis, management of GCT patients and estimation of the therapy success. The data document a strong association of HERV-K(HML-2) antibodies and the clinical manifestation of the disease and therapy success. HERV-K(HML-2) antibodies seem to have an important diagnostic value as well as indicator of chemotherapy success.

Epstein-Barr virus (EBV) is a human tumour virus that efficiently growth-transforms primary human B-lymphocytes in vitro. The viral nuclear antigen 2 (EBNA2) is essential for immortalisation of B-cells and stimulates viral and cellular gene expression through interaction with DNA-bound transcription factors. Like its cellular homologue Notch, it associates with the DNA-bound repressor RBPJj (CSL/CBF1) thereby converting RBPJj into the active state. For instance, both EBNA2 and Notch activate the cellular HES1 promoter. In EBV-transformed lymphocytes, the RNA of the NP9 protein encoded by human endogenous retrovirus HERV-K(HML-2) Type 1 is strongly up-regulated. The NP9 protein is detectable both in EBV-positive Raji cells, a Burkitt's lymphoma cell line, and in IB4, an EBV-transformed human lymphoblastoid cell line. NP9 binds to LNX that forms a complex with the Notch regulator Numb. Therefore, the function of NP9 vis-à-vis Notch and EBNA2 was analysed. Here, we show that NP9 binds to EBNA2 and negatively affects the EBNA2-mediated activation of the viral C-and LMP2A promoters. In contrast, NP9 did neither interfere in the activation of the HES1 promoter by Notch nor the induction of the viral LMP1 promoter by EBNA2. In an electrophoretic mobility shift analysis, NP9 reduced the binding of EBNA2 to DNA-bound RBPJj by about 50%. The down-regulation of EBNA2-activity by NP9 might represent a cellular defence mechanism against viral infection or could, alternatively, represent an adaptation of the virus to prevent excessive viral protein production that might otherwise be harmful for the infected cell.

The present investigation was carried out to estimate the prevalence of EBV‐associated cases among gastric carcinoma (GC) patients of Russia and the Republics of the former Soviet Union (FSU). With this aim, formalin‐fixed paraffin‐embedded blocks from 206 gastric carcinomas obtained from patients of the Cancer Research Center, Moscow, were investigated by EBV‐encoded RNA‐1 (EBER‐1) in situ hybridization applied to paraffin sections. As a result, 18 GC cases (8.7%) revealed uniform EBER‐1 expression restricted to the carcinoma cells. Hybridized signals not detected in non‐neoplastic gastric epithelium. EBV involvement was significantly more frequent among males, especially in tumors of less differentiated types (moderately differentiated tubular adenocarcinomas and poorly differentiated solid adenocarcinomas) and located in the upper stomach (cardia and middle). Most EBV‐positive GCs were characterized by strong lymphoid‐compartment involvement. Our findings concerning the distribution of EBV‐positive GCs by sex, site and hystological type are similar to those in Japan, however, EBV‐positive rate of GC cases in Russia is higher than in Japan and lower than in USA. Int. J. Cancer 73:786–789, 1997. © 1997 Wiley‐Liss, Inc.

We report the molecular characterization, with subtyping of both K1 and K14.1/K15 genomic regions, of seven new human herpesvirus-8 (HHV-8) strains from Russian patients with classical Kaposi's sarcoma. Phylogenetic studies, based on the complete K1 gene/protein analysis, indicate that six of these strains belong to the A subtype, with one belonging to the A4 group and exhibiting a unique deletion of 19 amino acids in the VR2 region at position 186-204. PCR-based studies of the K14.1/K15 genomic region indicate that four of the new strains were of the M subtype while three belonged to the P subtype. Our study indicates an important genetic diversity of the HHV-8 strains currently present in Russia, including a new peculiar strain possessing a unique deletion in the VR2 segment, and confirms the absence of correlation between the K1 and K14.1/K15 molecular subtypes, as M and P genotypes can be observed in the A K1 subtype.

It is still unknown what kinds of roles Epstein-Barr virus (EBV) infection that are highly specific to salivary gland lymphoepithelial carcinomas (LECs) play in their tumorigenesis.To clarify the significance of EBV in LECs, we paid particular attention to the LMP1 gene, which is responsible for triggering several pathways for activating transcription factors. Sixty-one cases of EBV positive LECs confirmed by PCR and in-situ hybridization were collected from various areas of the world and studied immunohistochemically for latent membrane protein-1. Furthermore, PCR for the LMP1 carboxyl (C)-terminus region was performed, and the PCR products were sequenced for detection of other mutational events. LMP1 gene products were immunohistochemically demonstrated in 51% of the cases, while PCR amplification of the LMP1 gene was successful in 41 cases (67%). Among them, a 30 bp deletion in the C-terminus of the LMP1 gene, which had been shown to be characteristic to EBV in Chinese nasopharyngeal carcinomas, was found in 20 cases (32%). Most of them were from Guangzhou, Chengdu and Taiwan, while most of the cases from Shanghai and other areas exhibited no 30 bp deletion. In addition, several point mutations including codon 338 of LMP1 were commonly shared by the cases with or without the 30 bp deletion. These results indicate that there are 2 major genomic variations of EBV infecting salivary gland LECs. The frequent mutational events in the C-terminus in addition to the 30 bp deletion also seem to be critical for the pathogenesis because such mutational events may possibly promote cellular proliferation.

A quantitative in vivo assay for evaluating the tumorigenicity of Burkitt's lymphoma (BL) cell lines in nude mice is described. It is based on the dose-response kinetics of BL cell lines in pre-irradiated (480 rad) nude mice following the s.c. injection of 4 different cell doses. This model system was used to estimate the xenografting potential of 26 BL cell lines derived from BL patients of different geographic and ethnic origins, as well as lymphoblastoid cell lines (LCLs) established by Epstein-Barr virus (EBV) immortalization of normal B lymphocytes. The results indicate that most BL cell lines are tumorigenic, but LCLs fail to produce progressively growing tumours in nude mice. However, BL cell lines revealed individual degrees of tumorigenicity and accordingly could be divided into 4 groups with high, moderate, low or no tumorigenicity. Preliminary attempts to correlate the xenografting phenotype of BL lines with other characteristics indicate that: (1) the aberrations of chromosome 1 are more often encountered in cell lines with high and moderate tumorigenicity; (2) EBV-positive BL lines do not reveal a higher tumorigenic phenotype in comparison with EBV-negative ones; (3) cell lines carrying translocations t(8;22) and t(2;8) might fall more frequently in the group of lines with high and moderate tumorigenicity; and (4) when LCLs grow in nu/nu mice, rejection always occurs and is associated with massive tumour necrosis. These findings suggest that the tumorigenicity of BL cell lines in immunosuppressed animals is not related with EBV, but with certain chromosomal abnormalities (BL-specific and non-specific) indicating that this in vivo model system can be instrumental for the identification of other factors or stages involved in BL development.