B cell activating factor ( BAFF ) in the natural history of chronic hepatitis C virus liver disease and mixed cryoglobulinaemia

Summary B cell activating factor ( BAFF ) plays a crucial role in the process of development, maturation and activation of B lymphocytes. C hronic h epatitis C virus ( HCV ) infection is characterized by multiple B cell disorders. It is a major cause of type II mixed cryoglobulinaemia ( MC ). We measured serum BAFF levels in several clinical situations to elucidate the potential role of BAFF in chronic HCV infection. We used a commercially available solid phase enzyme‐linked immunosorbent assay. We estimated serum BAFF in stored sera from uninfected controls ( n  = 8), patients with chronic hepatitis B virus infection HBV ( n  = 5) and chronic HCV infection with ( n  = 16) and without mixed cryoglobulinaemia ( n  = 14). In two patients with HCV and MC we correlated BAFF with HCV RNA after pegylated interferon (peg‐ I ). We correlated serum BAFF levels at baseline and at 12 weeks with treatment response: sustained virological response SVR ( n  = 5), non‐responders ( n  = 6) and relapsers ( n  = 2). Finally, we estimated BAFF levels after complete depletion of B cells with rituximab in patients with chronic HCV with MC ( n  = 3). Serum levels of BAFF were increased in chronic HCV with MC , but not in chronic HBV infection, suggesting an association between BAFF and cryoglobulinaemia. Peg‐ I increased BAFF levels in serum and this paralleled HCV RNA very closely. Serum BAFF levels at week 12 of therapy with peg‐ I and R were significantly higher in responders than non‐responders. Finally, B cell depletion was associated with markedly increased levels of BAFF .