In Western countries, chronic hepatitis C virus (HCV)-infection mostly affects former and active substance users. The effect of active substance use on interferon (IFN)-responsiveness and therapy efficacy is not well understood. In this study, we compared natural killer (NK) cell activity and function in healthy controls and chronic HCV-infected patients with and without active substance use, as well as the early effects of antiviral therapy with peg-IFN and ribavirin. No differences were observed between chronic HCV patients and healthy individuals in the number and frequencies of CD56dim and CD56bright NK cells. Also, IL-12/18-induced IFN-gamma production by NK cells was comparable between all groups, whereas the cytotoxic ability of NK cells (granzyme and CD107a levels) was more potent in HCV-infected patients as compared to healthy controls, and highest in non-substance users. Moreover, at baseline, the activation of NK cells was significantly lower in HCV-infected patients who used substances, when compared to healthy individuals. Therapy-induced viral load reduction assessed early at day 7 showed a similar decline in substance users and non-substance use HCV patients, with 25% substance users and 17% non-substance users testing HCV-RNA negative at day 7. Furthermore, early during IFN-based therapy, NK cells from HCV patients remained responsive to IFN, and only a minor decline in the degree of STAT-1 phosphorylation was observed irrespective of substance use. These findings were further supported by comparable in vitro p-STAT-1 induction in all three experimental groups. Despite subtle differences at baseline between healthy individuals and chronic HCV patients, we observed that active substance use in chronic HCV-infected patients did not affect the immune responsiveness to IFN early after start of treatment, and thus, we found no evidence - from an immunological point of view - that antiviral therapy of our cohort of HCV-infected patients with active substance use is less efficient.

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Keywords NK cells, Viral hepatitis
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Journal Antiviral Research
Hotho, D.M, Kreefft, K, Groothuismink, Z.M.A, Janssen, H.L.A, de Knegt, R.J, & Boonstra, P.A. (2013). Natural killer cell activity and function in chronic HCV-infected patients during peg interferon and ribavirin: Early effects of active substance use. Antiviral Research, 97(3), 347–355. doi:10.1016/j.antiviral.2012.12.025