Adamantanes (amantadine and rimantadine) and neuraminidase inhibitors (oseltamivir and zanamivir) have been commonly used in the treatment and prophylaxis of influenza A virus infections. However, recent studies have reported that some mutations in NA and M2 proteins could confer resistance of influenza A viruses to these drugs. In this study, amino acid sequences of M2 proteins of 29 H5N1 virus strains circulating in poultry reared in Northern Vietnam during period from 2008 to 2009 were analyzed to detect mutations conferring resistance to adamantanes. RNA of H5N1 virus strains were used as templates for full-length M segments amplification by a two step RT-PCR method. The DNA amplicons were then ligated with pJET1.2/blunt vector to generate recombinant plasmids containing M gene sequences of the H5N1 virus strains. Nucleotide sequences of M segments were determined by Sanger's method then analyzed by the appropriate software. In the study, the authors found that 4 strains having mutations conferring resistance to adamantane, including: TMU019 with V27 A mutation; TMU016 with S31N mutation; TMU012 and TMU013 with double mutations A30T and S31N. The result indicated that H5N1 viruses circulating in poultry could have natural mutations conferring resistance to adamantanes. Therefore, it is important to continue studying and detecting mutations related to the drug resistance of H5N1 viruses as well as developing new antiviral drugs that can be used in the treatment and prophylaxis of H5N1 virus infections caused by resistant strains.
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