Background Apart from systemic symptoms of viral infection parvovirus B19 (B19) could lead to acute and chronic arthropathy. It has been found in synovial tissue of rheumatoid arthritis (RA) patients, sometimes, being associated with some forms of undifferentiated arthritis. Possibly, it could promote inflammation in various forms of arthritis.

Objectives To determine the expression of B19 antigens in different compartments of synovial membrane; correlate these findings to the estimated synovitis score.

Methods 7 RA and 54 osteoarthritis (OA) patients were enrolled in this study. nPCR was used to detect the presence of B19 genomic sequence in 61 samples of synovial tissue. PCR B19 positive tissue samples were immunohistochemically treated with the anti-B19 antibodies detecting B19 capsid proteins' VP1/VP2 expression estimated thereafter semiquantitatively. The intimal and subintimal layers of synovium as well as vasculature were estimated. Synovial inflammation was evaluated using synovitis score.

Results 3 RA and 3 OA patients were PCR B19 tissue positive. B19 antigens' expression was observed in synovial lining, immune infiltrates and vascular endothelium. Correlation between B19 expression observed in synovial cells and inflammatory infiltrates' lymphocytes and macrophages was r=0.555 (p<0.0001) and r=0.793 (p<0.0001), respectively. Likewise, correlation between vascular endothelial B19 expression and synovial lymphocytic infiltrates was demonstrated r=0.616 (p<0.0001). Determined synovitis score varied from low up to intermediate revealing median value 2. Simultaneously, there was no correlation found between the synovitis score and B19 antigens' expression.

Conclusions B19 capsid proteins' VP1/VP2 expression is detectable in different structural constituents of synovial membrane. Under conditions studied, the tissue expression of B19 antigens does not correlate with the inflammatory indices scored.

Disclosure of Interest None declared