Skewed B cells in chronic hepatitis C virus infection maintain their ability to respond to virus‐induced activation

Chronic hepatitis C virus (HCV) infection is characterized by persistent B‐cell activation, with enhanced differentiation and reduced proliferative ability. To assess the possible role of HCV in altering B‐cell subset distribution, we examined ex vivo frequencies and B‐cell inhibitory receptor expression in 37 chronic HCV‐infected patients and 25 healthy donors (HD). In addition, we determined whether short‐term exposure to culture‐derived HCV (HCVcc) resulted in B‐cell subset skewing and/or activation. There was a statistically significant increase in the frequencies of immature transitional, activated memory and tissue‐like memory (TLM) B cells in HCV‐infected patients compared with HD. We also found that the frequency of memory B cells correlated with serum HCV RNA levels. The proportion of B cells expressing the marker of exhaustion Fc receptor‐like 4 (FcRL4) was generally low even though significantly higher in the patients' memory B‐cell compartment compared with HD, and a positive correlation was found between the frequencies of the patients' TLM FcRL4+ B cells and serum alanine aminotransferase and histological activity index at liver biopsy. Exposure to cell‐free HCVcc in vitro did not result in B‐cell skewing but induced significant activation of naïve, TLM and resting memory B cells in HCV‐infected patients but not in HD, in whom cell‐associated virus was an absolute requirement for activation of memory B cells. These findings provide corroborative evidence in favour of significant B‐cell subset skewing in chronic HCV infection and in addition show that expression of exhaustion markers in selected B‐cell subsets does not impair virus‐induced B‐cell activation.