Parvovirus B19 as possible triggering factor of endothelial and fibroblast alterations in systemic sclerosis

Background: Background. Numerous environmental, toxic and infectious agents have been proposed as possible triggering factors of systemic sclerosis (SSc); nevertheless its etiology remains still obscure. The disease is characterized by progressive fibrotic alterations of the skin and visceral organs. The pathogenesis may reflect a humorally mediated endothelial cell damage responsible for diffuse microangiopathy in concert with the overproduction of collagen by altered fibroblasts. Recently, two viruses, human cytomegalovirus and parvovirus B19 (B19), has been proposed as causative agents for SSc. HCMV seems to exert its pathogenetic potential through humoral immune-mediated pathogenetic mechanisms responsible for endothelial damage. While, persistent B19 infection has been demonstrated in a significant number of bone marrow and skin biopsy specimens of SSc patients.Objectives: Objectives. In order to further elucidate a role for B19 in the pathogenesis of SSc.Methods: Methods. Twelve patients who fulfilled the ACR preliminary criteria for SSc classification were randomly investigated. Patients were serologically screened for B19 infection; in addition, solution phase polymerase chain reaction (PCR) and reverse transcriptase in situ PCR (RT in situ PCR) for B19 and tumor necrosis factor-alpha (TNF-alpha) mRNA was performed on skin tissue. Two control groups were assessed for B19 and TNF-alpha expression: one with irrelevant primers and the other representing 18 cases of inflammatory skin lesions where the etiology was known and unrelated to B19 infection. In addition, frozen and paraffin-embedded tissues procured from skin lesions unrelated to B19 infection were assessed for B19 genome. In all cases, pretreatment with RNase was also performed to verify that any positive signal was indeed RNA based.Results: Results. Diffuse cutaneous involvement was seen in 7 SSc patients, and limited in five. All patients had a specific autoantibody (anticentromere, antinucleolar, anti-Scl70); 11/12 had lung involvement, whereas 8/12 had myocardial disease. Serum anti-B19 IgG antibodies were recorded in 9/12 patients, including IgM type in 2 cases. Solution phase PCR showed B19 DNA in the skin and/or bone marrow in 6 cases. In these latter, RT in situ PCR demonstrated B19 and TNF-alpha mRNA in endothelia, fibroblasts, mast cells, and perivascular inflammatory cells. Immunofluorescent studies revealed prominent deposition of C5b-9 within the cutaneous vasculature from biopsies of all patients tested. The control samples were negative for B19 DNA, TNF-alpha RNA, and C5b-9 deposition.Conclusion: Conclusion. The infection of endothelia and fibroblasts by B19, and in particular, the consequent enhanced TNF-alpha expression may be of pathogenetic importance in SSc. Moreover, the vascular deposition of C5b-9 suggests a role for humoral immunity possibly induced by a state of endothelial neoantigenicity evoked by virus-mediated cell injury.