Circulating and inducible IL-32α in chronic hepatitis C virus infection

Background: Interleukin 32 (IL-32) is a recently described pro-inflammatory cytokine implicated in chronic hepatitis C virus (HCV)-related inflammation and fibrosis. IL-32α is the most abundant IL-32 isoform.

Methods: Circulating IL-32α levels were documented in patients with chronic HCV infections (n = 31) and compared with individuals who spontaneously resolved HCV infection (n = 14) and HCV-naive controls (n = 20). In addition, peripheral blood mononuclear cells (PBMC) from the chronic HCV (n = 12) and HCV-naive (n = 9) cohorts were investigated for responses to HCV core and non-structural (NS)3 protein induced IL-32α production. Finally, correlations between IL-32α levels, hepatic fibrosis and subsequent responses to interferon-based therapy were documented in patients with chronic HCV.

Results: Circulating IL-32α levels in patients with chronic HCV were similar to those of spontaneously resolved and HCV-naive controls. HCV protein induced IL-32α responses were similar in chronic HCV patients and HCV-naive controls. In patients with chronic HCV, serum IL-32α levels correlated with worsening METAVIR fibrosis (F) scores from F0 to F3 (r = 0.596, P < 0.001) as did NS3 induced IL-32α responses (r = 0.837, P < 0.05). However, these correlations were not sustained with the inclusion of IL-32α levels at F4 scores, suggesting events at F4 interfere with IL-32α synthesis or release. In chronic HCV patients who underwent treatment (n = 28), baseline in vivo and in vitro induced IL-32α concentrations were not predictive of therapeutic outcomes.

Conclusions: IL-32α activity is associated with worsening fibrosis scores in non-cirrhotic, chronic HCV patients.