New strategy against killer virus H5N1

Colorized transmission electron micrograph of Avian influenza A H5N1 viruses. (source: wikipedia)

H5N1 is a subtype of the Influenza A virus that has caused widespread infections in poultry and wildbirds. It can also produce illness in humans. However, current vaccines are still of limited effect. Recently, a research group headed by HE Hongxuan with the CAS Institute of Zoology, in cooperation with their co-workers from Tsinghua University, revealed that short interfering RNA (siRNA) specific for conserved regions of the H5N1 AIV genome can effectively inhibite its replication in both cell lines and embryonated chicken eggs. Their work was published in a recent issue of Journal of Biotechnology.
Actually, scientists had already made attampts to suppress H5N1 AIV production by using siRNA sollutions, but their approaches were unseccessful. Through extensive study and experiments, Prof. He and his collegues found that the "vehicle" adopted to transduce siRNA into the animal cells was adenovirus vector rather than DNA circle and the immune system could then eleminate the adenovirus, which caused the inefficacy of the method.
The siRNA expression plasmid, which is suitable for mass production, is a type of DNA circle and was used in He's study. Previous studies showed that a portion of the genome of a number of AVI mutants developed to have strong conservation, so the research group specified the design of the siRNA expression plasmid for the conserved regions of the AIV genome, which then showed potent inhibition effect on the AVI replication. The scientists hope that this kind of siRNA expression plasmid can make the same effect on other AVI mutants.
Although the work is still preliminary, it provides a basis for the development of siRNA as prophylaxis and therapy for AIV infection in birds and humans. This approach is of large potential value though there are still challenges to be overcome, says Prof. Herman Eisen, a virologist from the Massachusetts Institute of Technology.
The research was under the joint auspices of the National Natural Science Fundation of China, the National Hi-Tech Research and Development Program of China (dubbed the "863 Program") and a Sino-US cooperative project.