From the Journals

Model finds spontaneous HCV clearance higher than previous estimates



Up to 40% of hepatitis C virus (HCV)–infected individuals clear their infection spontaneously, based on the results of a new mathematical model of HCV transmission and clearance, according to a report published online in the International Journal of Infectious Diseases.

Houssein H. Ayoub, PhD, of Cornell University, New York, and his colleagues conducted a study on HCV clearance. Previous estimates using empirical data indicated that the HCV clearance rate was about 25% after and acute infection duration of 16.5 weeks, according to Dr. Ayoub and his colleagues.

They developed a model to describe HCV transmission and a virus clearance rate (fclearance), defined as the proportion of HCV-infected persons who spontaneously clear their infection after the acute stage. The rest of the infected population (1–fclearance) become chronically infected and positive for both HCV antibodies and HCV RNA.This was estimated by fitting the model to probability-based and nationally representative, population-based data from Egypt (2008 and 2015), and the U.S. National Health and Nutrition Examination Surveys (NHANES A and NHANES B) data. Their model showed that fclearance was related to the HCV viremic rate approximately as fclearance = 1.16 x (1–HCV viremic rate). The HCV viremic rate was defined as the proportion of individuals who were positive for HCV antibodies and HCV RNA out of all who were positive for HCV antibodies positive, regardless of RNA status, as measured in a cross-sectional survey.

Antibody prevalence in Egypt was estimated at 14.7% in 2008 and 10.0% in 2015, while the viremic rate was assessed as 67.1% and 70.2%, respectively. For the United States, the pooled antibody prevalence from the NHANES A data between 1999 and 2012 was an estimated 1.4% and the pooled viremic rate was estimated at around 74%. The NHANES B data used as the denominator for HCV viremic rate both individuals confirmed as HCV Ab positive and those with an undetermined HCV antibody status. (NHANES laboratory procedures can provide this added information because of their subsequent testing of undetermined HCV antibody results for HCV RNA positivity.) This change to the formula yielded a viremic rate of 64.6%.

They found that fclearance was an estimated at 39.9% and 33.5% for Egypt in 2008 and 2015, respectively, and 29.6% and 49.9% for NHANES A and NHANES B, respectively.

“Empirical measures from longitudinal cohort studies may have underestimated the ability of the host immune system to clear HCV infection. This finding may have also implications for our understanding of the biological determinants of HCV spontaneous clearance. It may hint that a strategy for HCV vaccine development could be a vaccine that does not necessarily prevent infection, but modulates immune response towards conditions that increase the capacity of the host immune system to clear HCV infection spontaneously,” the researchers concluded.

The study was funded by the Qatar National Research Fund and Cornell University. The authors reported no conflicts of interest.

SOURCE: Ayoub HH et al. Int J Infect Dis. 2018 Jul 18. doi: 10.1016/j.ijid.2018.07.013.

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