The role of nitric oxide in infectious disease is gaining increased attention because antiviral effects of nitric oxide. In addition, there is evidence that nitric oxide synthase-2 expression was noted in chronic hepatitis C found within mononuclear cells.

We studied serum levels of nitrite and nitrate before and during interferon alpha therapy in 66 patients with chronic hepatitis C.

There was no significant difference of their levels between the healthy control subjects and the patients before the treatment with interferon (55.9±21.8μM vs. 60.9±30.0μM). Their levels were determined at 2 weeks after the initiation of treatment with interferon and compared with those before the treatment in the patients with chronic hepatitis C. In the total patients treated, there was no significant difference between their levels before and at 2 weeks after the treatment (60.9±30.0μM vs. 65.5±30.0μM, P=0.14). However, when the levels were compared between sustained responders, in whom hepatitis C virus was eradicated, and non-responders, in whom the virus was not eradicated, the former had significantly higher levels of nitrite and nitrate than the latter at 2 weeks after the initiation of treatment (83.7±40.9μM vs. 57.6±19.5μM, P<0.01). The multivariate logistic regression analysis showed that the rise of nitrite and nitrate was an independent predictive factor for efficacy of interferon treatment.

Nitric oxide may be an important factor for antiviral therapy by interferon treatment for chronic hepatitis C, which suggests an additional therapeutic pathway for further study.