Matthew Durrant and Dennis Eggett, Brigham Young University
Life Sciences
The drugs amantandine and rimantadine were previously used to treat influenza A infections in humans. In 2005, a mutation in the Influenza A M2 channel conferred resistance to these drugs, rendering them obsolete against treating influenza. The S31N amantadine-resistance mutation in the influenza A M2 sequence currently occurs more frequently in nature than the S31 wild type. Overcoming this mutation with new drug compounds is the focus of Influenza A M2 channel researchers. However, there are several other identified mutations that have also been shown to confer resistance to these drugs. These other mutations are thought to occur only in small frequencies in nature. A statistical analysis of 1,007 unique M2 protein sequences shows an enhanced frequency for the S31N/V27A dual amantidine resistant mutation in recent years, especially in swine, compared to expected frequencies based on the occurrence rates of individual mutations in wild type (S31) M2. The development of the S31N/V27A variant in the Midwestern US swine may be a harbinger of novel human strain development. At the same time, the different propensities for the V27A as compared to the V27T dual mutant may reflect differences in viral fitness or protein energetics, and this information could be exploited to focus drug development so as to reduce further drug insensitivity. V27A/S31N is a possible path forward for the evolution of M2, which may convey a new level of drug resistance and should receive attention in drug design.