B-Lymphocyte stimulator (BLyS) up-regulation in mixed cryoglobulinaemia syndrome and hepatitis-C virus infection

Objectives. To investigate the role of B-Lymphocyte stimulator (BLyS) in mixed cryoglobulinaemia syndrome (MCsn), a systemic vasculitis associated with a high risk to develop lymphoma, since BLyS up-regulation may favour both autoimmunity and lymphoproliferation. Methods. BLyS serum levels were analysed by enzyme-linked immunosorbent assay (positive when > 0.85 ng/ml) in 66 patients with MCsn, 54 (81.8%) of whom were positive for hepatitis-C virus (HCV) infection. Thirty-three HCV-positive patients without MCsn were also studied. Patients were compared with 48 healthy blood donors (HBDs). BLyS modifications after antiviral therapy were also studied. Results. A significantly higher frequency of BLyS serum positivity was detected both in MCsn patients and in HCV-positive patients without MCsn (37.9 and 30.3%, respectively) when compared with HBDs (4.2%) (P < 0.0001 vs MCsn and P = 0.0026 vs HCV-positive patients without MCsn, respectively). BLyS appeared significantly higher in MCsn (3.70 +/- 2.97 ng/ml) than in HCV-positive patients without MCsn (1.56 +/- 0.63 ng/ml; P = 0.0044). BLyS expression did not correlate with rheumatoid factor levels, cryoglobulin levels or definite MCsn-related systemic features. High BLyS levels were significantly associated only with MCsn-related overt lymphoproliferative disorder. Finally, antiviral treatment significantly increased BLyS levels, independently from HCV-RNA negativization. However, BLyS normalization was noticed after both HCV-RNA negativization and suspension of antiviral therapy by preliminary data. Conclusions. BLyS is up-regulated and may play a pathogenetic role in a fraction of patients with MCsn, similarly to other autoimmune diseases. HCV infection likely represents the early event leading to BLyS up-regulation in this setting. BLyS is up-regulated during antiviral treatment. Overall, these data provide new insights for BLyS and virus-related autoimmunity, lymphoproliferation and possible treatment strategies.