News at Medicine - May 2009 - Hepatitis C patients likely still contagious after treatment

Hepatitis C patients likely still contagious after treatment
May 5, 2009
Patients with chronic hepatitis C (HCV) that has been resolved through therapy or immune response may still be able to infect others with the virus. That finding is from a new study led by Dr. Thomas Michalak, Canada Research Chair in Viral Hepatitis/Immunology at Memorial University. The study was published in the May issue of Hepatology.

About 170 million people worldwide are infected with hepatitis C virus, which can progress to chronic hepatitis, cirrhosis and even liver cancer. In some individuals, the infection seems to resolve, either spontaneously from the efforts of the immune system, or after treatment with interferon and ribavirin.

Patients who achieve a sustained viral response show no clinical or biochemical evidence of liver disease and standard tests can no longer detect the virus in their blood. However, more sensitive research tests are finding that such patients often still have miniscule amounts of the virus in their bodies. No one knows if these trace remainders are infectious.

The research study led by Dr. Michalak examined this question using a system that allows for propagation of HCV in human T cells in vitro.

The research team began with nine patients with HCV who had achieved a sustained viral response that persisted for at least two years after treatment. HCV RNA was detectable in their blood only with the more sensitive tests.

The researchers set up12 cultures of lymphoid cells from healthy donors, and exposed them to plasma or to supernatants of cultured circulating lymphoid cells from the HCV patients. Eleven of the cell cultures became HCV RNA positive. Furthermore, HCV from three of the nine patients was able to establish active HCV replication in the cultures.

“These findings provide in vitro evidence that trace quantities of HCV persisting in the circulation for a long time after therapeutically induced resolution of CHC can remain infectious,” said Dr. Michalak.

Interestingly, he added, HCV replication in the T cells was prevented after neutralization of the virus and by treatment with interferon.

This study is the first to investigate the infectivity of HCV traces that remain when the infection is not obvious on inspection. It agrees with previous animal studies of the same question. 

“Our present findings reveal that HCV circulating in some individuals with resolved hepatitis C is capable of inducing productive infection in vitro at doses of 20 to 50 copies,” said Dr. Michalak. “This can be interpreted as a strong indication of potential virus infectivity in vivo.”

Hepatology is a journal published by John Wiley & Sons on behalf of the American Association for the Study of Liver Diseases (AASLD). The article is also available online at Wiley Interscience (