Amantadine-Resistant among Seasonal H1N1 and 2009 Pandemic Isolated of Influenza A Viruses in Iran

Background and Aims: Influenza A viruses are important pathogens for humans especially in pandemic episodes. Two adamantane derivates, amantadine and rimantadine, are used for prophylaxis and treatment of influenza A virus infections. However, single amino acid substitutions in the M2 transmembrane domain which lead to amantadine resistance of these viruses occur at residues 26, 27, 30, 31 or 34. Rates of resistant viruses have been increasing globally. Methods: In this report, 21 specimens of seasonal H1N1 and pandemic influenza A viruses which grew on MDCK cell line were studied for detection of amantadine resistant viruses. After RT-PCR M2 gene of samples were sequenced. In addition, as confirmatory assay, amplification of pandemic influenza A viruses on amantadine treated MDCK cell line and evaluation of TCID50 assay, were accomplished. Results: All seasonal influenza A viruses were amantadine sensitive but none of the 2009 pandemic influenza A viruses where us none of the 2009 pandemic influenza A virus were sensitive. Conclusion: Considering emergence of new influenza A virus variant, and resistance to amantadine, it is noteworthy that application of amantadine in new variant A/H1N1 influenza viruses might not be effective.