Human endogenous retrovirus HERV-K(HML-2) Rec expression and transcriptional activities in normal and rheumatoid arthritis synovia.

OBJECTIVE: Despite abundance in the genome, the possible functions of human endogenous retrovirus (HERV) sequences are not well understood. The involvement of HERV in various disease conditions, such as germ cell tumors or autoimmune diseases like rheumatoid arthritis (RA), has been suggested. We investigated expression of HERV-K(HML-2) env-derived transcripts in normal and RA synovia. METHODS: We analyzed HERV-K(HML-2) expression on the mRNA and protein level by RT-PCR analysis and immunofluorescence labeling of the HERV-K(HML-2) Rec (formerly cORF) protein. We examined synovial cell cultures from normal synovia (n = 9), from patients with RA (n = 26), and osteoarthritis (OA, n = 4), and uncultured synovial tissues (RA, n = 12; normal synovia, n = 1). RESULTS: HERV-K Rec protein was expressed in all normal synovial specimens, and in the majority of RA and OA cases. We demonstrate for the first time expression of HERV-K protein in synovial tissue. RT-PCR and sequence analysis of cloned RT-PCR products confirmed expression of spliced HERV-K(HML-2) env transcripts in normal and in arthritic synovia. In addition to rec mRNA, several alternatively spliced transcripts, including np9, were identified. However, different amounts of the various RT-PCR products indicate different expression levels of HERV-K(HML-2) env-derived transcripts in RA compared to normal synovia, with apparently lower expression levels in arthritic synovia. CONCLUSION: These findings imply a physiological role of HERV-K(HML-2) Rec in synovial tissue. Differences in the expression of HERV-K env-derived transcripts in RA synovia may be caused by disease-specific changes in the general expression pattern.

Latent Epstein-Barr virus (EBV) infection and cytomegalovirus (CMV) infection in synovial tissue of autoimmune chronic arthritis determined by RNA- and DNA-in situ hybridization.

In rheumatoid arthritis (RA) viral triggers, especially Epstein-Barr virus (EBV) and cytomegalovirus (CMV), have been suggested. By PCR analysis DNA of several viruses among which EBV, CMV, and parvovirus B19 (B19) has been detected in RA synovial fluid and synovial tissue. In 63 synovial tissues of 29 rheumatoid arthritis (RA), 6 psoriatic arthritis (PsA), 26 reactive arthritis/synovitis (rA/S), and two normal synovial cases, we recently could demonstrate a high percentage of replicative B19 infection within the synovial tissue, being significantly more frequent in autoimmune arthritis. To further investigate the influence of synovial virus infections in rheumatoid arthritis, we now analyzed the same sample of synovial tissues for CMV and EBV infections by DNA-in situ hybridization (CMV), EBER1/2-RNA-in situ hybridization (EBV), and immunohistochemistry. A significant latent EBV infection of synovial lining cells, synovial fibroblasts, and/or infiltrating lymphocytes was identified in 5/29 (17.2 %) RA, 1/6 (16.7%) PsA, and to a much lower degree in 1/26 (3.8%) rA/S specimens. CMV-DNA was detected in 31% of RA, 3/6 (50%) of PsA, and 11.5% of rA/S. Immunohistochemical analysis of CMV early antigen revealed replicative CMV activity in 20.7% of RA and 2/6 (33.3%) of PsA specimens but not in reactive arthritis synovia. Comparative analysis of the EBV-, CMV-, and published B19-data demonstrated that relevant synovial virus infections in general and furthermore double or multiple infections are far more common in autoimmune arthritis than in rA/S. A triple virus infection was found solely in RA in 10.3% of cases. The evidence of increased synovial persistence of EBV, CMV, or B19 either alone or even more as coinciding infections may further reinforce the notion of a primary role of these viruses in autoimmune arthritis.

Detection of parvovirus B19 capsid proteins in lymphocytic cells in synovial tissue of autoimmune chronic arthritis.

The pathogenic influence of viral agents in chronic inflammatory joint diseases like rheumatoid arthritis has been discussed for many years. More recently, DNA of several viruses, among them parvovirus B19 (B19), was traceable by PCR analysis in synovial fluid and synovial tissue. To investigate the potential role of parvovirus B19 in rheumatoid arthritis, we analyzed the expression of B19 VP1/VP2 proteins by immunohistochemistry in paraffin sections of 63 synovial specimens in rheumatoid arthritis (RA; n = 29), psoriatic arthritis (PSA; n = 6), nonspecific arthritis or synovitis (n = 26), and normal synovia (n = 2). Thereby we could demonstrate replicative virus infection in a variable number of cells in about 90% of rheumatoid specimens and in four of six (66%) cases of psoriatic arthritis, but only in 38% of cases with chronic reactive inflammation and one case of normal synovia. In virus-positive rheumatoid specimens, moreover, the average number of affected cells was significantly higher than in virus-expressing synovia of nonspecific reactive inflammation. These findings support the importance of B19-viral infection in the pathogenesis of chronic arthritis. B19-positive cells in the synovia could be ascribed to CD20- or CD3-positive B- or T-lymphocytes by double immunostaining. Based on these results, B19 infection of lymphocytic cells also seems possible.