Sun, 21st Oct 2007
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Scientists in the US have uncovered how the body tackles certain viral infections, and the results might help to produce better ways to treat Hepatitis C. Hepatitis C is a blood-bourne viral infection spread by needle sharing, use of contaminated blood products and by sex, and it affects about 1% of the population in the western world. 80% of individuals who catch it develop a chronic infection which causes liver injury and can lead to cirrhosis in about 20% of cases. Recently doctors have found that long-term therapy with a immune-regulating hormone called alpha-interferon can enable the immune system to overcome the virus and eliminate it from the body, although exactly how remained a mystery.
Now, writing in Nature, UC San Diego's Michael David and his colleagues have uncovered the mechanism, and in the process revealed a previously unknown mechanism by which the body deals with viral infections. The team treated cultured cells with interferon and then studied the levels of short pieces of genetic material called micro RNAs, which have in recent years been shown to play key roles in regulating gene activity. Using this technique the researchers pinpointed 30 different micro RNAs that altered their levels in the presence of interferon. They then compared these RNA sequences with the hepatitis C genome to see if there were any matches. What they were looking for were sequences in the virus that were mirror images of the micro-RNA because when this happens the micro-RNA can bind to its mirror image viral gene and disable it. The researchers found 8 micro RNAs that were direct hits in the hepatitis C genome. To find out whether they could affect the growth of the virus they added synthetic versions of each of the micro RNAs to hepatitis C infected cells, which reduced the turnover of the virus in the cells by 70%.
This approach could hold the key to effective new therapies for hepatitis C in the future, and may also spare patients the unpleasant flu-like side effects of interferon therapy.