New research from the University of New South Wales shows some people may repeatedly be able to clear hepatitis C virus from their bodies, without any biological traces of the potentially serious infection.
The surprise finding could lead to the development of a vaccine against the virus, which currently affects nearly 4 million Americans and 170 million people worldwide. HCV is responsible for 8,000 to 10,000 deaths per year in the United States and is the number one cause of liver transplants. HCV can also lead to cirrhosis, end-stage liver disease, and liver cancer. Over 30,000 new cases are diagnosed each year.
The study found some individuals with high-risk behaviour, involving blood-to-blood contact, appear to develop "protective immunity" against the virus, thereby becoming resistant to persistent infection.
The researchers identified 160 prisoners who were free of the infection and tracked them on a monthly basis whilst in gaol. This entailed blood collection and recording episodes likely to put the prisoners at risk for transmission of hepatitis C, such as injecting drug use or tattooing.
Over the course of the study, four prisoners became infected with hepatitis C, yet they all went on to clear the virus without suffering any symptoms or developing antibodies against the virus. Instead it appeared that another arm of the immune system based on specialised white blood cells, or T cells, might be active in fighting the virus.
"It is possible that they had been infected in the past, perhaps on several occasions and that may be why they were able to clear the virus efficiently and without developing antibodies," said UNSW Professor Andrew Lloyd, who is in the School of Medical Sciences.
This cellular immunity appears similar to that found in some Kenyan prostitutes who appear to have protective immunity from HIV. These prostitutes are resistant to becoming HIV positive, despite repeatedly having unprotected sex with clients who are infected.
The researchers have found a similar pattern of cellular immunity to hepatitis C in another high-risk group - injecting drug users. They ultimately hope to reproduce a similar pattern of protective immunity with a synthetic vaccine.