Frequent infection with a viral pathogen, parvovirus B19, in rheumatic diseases of childhood

Objective. To find further evidence of the association of parvovirus B19 infection with juvenile rheumatic diseases, and to get new insights into the immunopathogenesis of these diseases. Methods. Paired serum and synovial fluid samples from 74 children with rheumatic disease were analyzed with respect to their content of viral DNA and antibodies directed against the B19 viral proteins VP1, VP2, and NS1. Control sera from 124 children with noninflammatory bone diseases or growth retardation were also analyzed. The sequence of the viral DNA, amplified by polymerase chain reaction (PCR), was determined. IgG-complexed virus was isolated from sera and synovial fluid by adsorption to protein A beads. The amount of free virus versus immunocomplexed virus particles was determined by quantification of the viral genomes by quantitative PCR. Results. Twenty-six of the 74 patients (35%) had detectable amounts of parvovirus B19 DNA in the serum (n = 22 [30%]) and/or the synovial fluid (n = 16 [22%]), whereas only 9 of the 124 control sera (7%) were positive for the viral DNA (P < 0.0001). Forty-six patients (62%) had serum IgG against the structural proteins, indicating past infection with B19. NS1-specific antibodies were detected in sera from 29 patients (39%) and 27 controls (22%) (P < 0.001). In addition, 3 patients (4%) showed VP2-specific IgM. In 15 patients, viral DNA could be repeatedly detected in followup samples of serum and synovial fluid. Sequencing revealed low-degree nucleotide variations that are in the range of genotype 1 of parvovirus B19. Immunocomplexed virus was present in varying amounts, both in the sera and in the synovial fluid samples. Conclusion. Parvovirus B19 is frequently found in serum or synovial fluid of children with rheumatism. The rate of persistent B19 infection in these patients is significantly higher than in age-matched controls.