( human-to-human transmission the world ...)Drug resistant avian influenza viruses more common in Southeast Asia than North America

human-to-human transmission, the world will face the threat of a serious pandemic," said Robert G. Webster, Ph.D., a member of the Infectious Diseases department and holder of the Rose Marie Thomas Chair at St. Jude. "Humans don��t have resistance to H5N1, and currently vaccines to H5N1 are still being developed. And, the available evidence shows that the most recent strains isolated from humans in Asia are no longer sensitive to inhibition by the amantadine family of drugs."

Resistance to the antiviral drug amantadine is caused by substitutions of one of five amino acids in the part of the M2 protein called the transmembrane domain-the part of M2 located within the coat of the influenza virus. The M2 protein is an ion channel located in the envelope of the virus that permits hydrogen ions (protons) to enter the flu virion. This influx of protons allows the virus to shed its coat after it enters a cell-an essential step in the replication of the virus. Amantadine inhibits the function of the M2 protein and thus stops viral replication.

"By analyzing the sequence of the transmembrane part of the M2 gene we were able to determine how frequently amantadine resistance occurs in avian influenza A subtypes isolated in various parts of the world-especially among those subtypes that had the potential to cause a pandemic," said Natalia A. Ilyushina, Ph.D., a postdoctoral fellow in the Infectious Diseases Department at St. Jude. First author of the Virology paper, Ilyushina did much of the work on this project.

The St. Jude researchers analyzed the M2 gene sequences from 60 influenza viruses isolated in Southeast Asia and 74 viruses from North America that represented the H5, H6, H7 and H9 subtypes. The scientists also examined information from the National Library of Medicine's GenBank database on 408 viruses isolated from avian hosts worldwide.

Based on the study, the St. Jude team reported that there were no avian amantadine-resistant str
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Source:St. Jude Children's Research Hospital

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