Clinical

Frequent HCV exposure tied to immune responses

Last Updated: 2008-08-01 16:54:48 -0400 (Reuters Health)

NEW YORK (Reuters Health) - Injection drug users who successfully clear HCV infection have a reduced risk of re-infection. Now, in long-term injection drug users frequently exposed to the hepatitis C virus (HCV), analysis of virus-specific immune responses has shown that resistance to re-infection is correlated with T cell responses.

Dr. Barbara Rehermann of the National Institutes of Health in Bethesda, Maryland and colleagues studied 66 individuals with long histories of injecting illicit drugs. They report their findings in the July 15th issue of the Journal of Infectious Diseases.

HCV-specific T cell proliferation and interferon gamma production were present in 94% of subjects who were enzyme immunoassay positive but non-viremic. This was true of only 45% of their viremic counterparts and 62% of the negative non-viremic subjects.

In addition, 90% of viremic subjects had neutralizing antibodies, compared to 56% of those who were positive but non-viremic, and none who were negative and non-viremic.

The widespread presence of antibodies in the non-viremic subjects is contrary to findings in other studies, say the investigators, and is most likely due to frequent HCV re-exposure because of continuing injection drug use.

Given that the reduced risk for HCV persistence in drug users with previous infection was correlated with T cell responses, the investigators conclude that "prolonged antigenic stimulation appears to be required to maintain humoral responses."

J Infect Dis 2008;198:203-212.