Severe fibrosis in hepatitis C virus‐infected patients is associated with increased activity of the mannan‐binding lectin (MBL)/MBL‐associated serine protease 1 (MASP‐1) complex

Summary Mannan‐binding lectin (MBL) binds microorganisms via interactions with glycans on the target surface. Bound MBL subsequently activates MBL‐associated serine protease proenzymes (MASPs). A role for MBL in hepatitis C virus (HCV) infection had been indicated by previous studies examining MBL levels and polymorphisms in relation to disease progression and response to treatment. We undertook this study to investigate a possible relationship between disease progression and functional MBL/MASP‐1 complex activity. A functional assay for MBL/MASP‐1 complex activity was employed to examine serum samples from patients with chronic HCV infection, non‐HCV liver disease and healthy controls. Intrapatient consistency of MBL/MASP‐1 complex activity levels was assessed in sequential samples from a subgroup of patients. Median values of MBL/MASP‐1 complex activity were higher in sera from patients with liver disease compared with healthy controls. MBL/MASP‐1 complex activity levels correlate with severity of fibrosis after adjusting for confounding factors ( P  = 0·003). MBL/MASP‐1 complex activity was associated more significantly with fibrosis than was MBL concentration. The potential role of MBL/MASP‐1 complex activity in disease progression is worthy of further study to investigate possible mechanistic links.