High rate of spontaneous negativity for hepatitis C virus RNA after establishment of chronic infection in Alaska Natives

Background. Hepatitis C virus ( HCV) leads to chronic infection in 70% - 85% of exposed patients. Spontaneous clearance of the virus after chronic infection is believed to occur rarely. Methods. Alaska Natives who tested positive for HCV antibodies were enrolled in a prospective study that began in 1994 and were followed up on a regular basis. Individuals who tested positive for HCV RNA on 3 separate dates, each of which were at least 1 year apart, were included. Being negative for the virus was defined as having at least 1 negative HCV RNA test result after chronic viremia had been established. Results. Of the 815 patients enrolled in the cohort, 139 met entry criteria and were observed for a mean period of 7.0 years. Eleven ( 8%) of the persons had at least 1 test in which HCV RNA was undetectable; 7 were classified as having either possible or probable clearance of the virus, corresponding to an annualized clearance rate of 0.74% per person-year ( 95% CI, 0.30% - 1.53%). Of 9 patients who underwent subsequent HCV RNA testing, 5 ( 56%) had negative test results. A low HCV RNA level was significantly associated with spontaneous nondetectability of HCV RNA. Conclusion. Spontaneous HCV RNA negativity during chronic HCV infection is a surprisingly frequent event and is associated with low HCV RNA titers. Knowledge of immunologic determinants of clearance may open up avenues of novel therapy.