H1N1 virus shows genetic mutation, 'but not a worry'

PUNE: The swine flu virus isolatedfrom the throat swab samples of three H1N1-infected patients at the NationalInstitute of Virology (NIV) has shown a small genetic mutation in the polymerase2 (PB2) gene, NIV director A C Mishra told TOI on Monday.However,Mishra said there was no cause for worry as the virus was still not resistant tooseltamivir, which is an active ingredient in Tamiflu. It may benoted that a small genetic mutation was earlier detected in the haemagglutinin(HA) region of the virus as well while testing the throat swab samples of twopatients who eventually succumbed to the H1N1 infection.The PB2mutation has previously been associated with increased efficiency of replicationand possible virulence changes in other influenza A viruses. “However, wedid not find such increased efficiency of replication or increased virulence inthe isolates of the swine flu virus in which we have noticed mutation of the PB2gene. The mutation is not very significant in that sense,” saidMishra.Consulting microbiologist and immunologist Siddharth Dalvisaid, “The PB gene makes a protein that is responsible for viralreplication. Since this enzymic protein is not directly involved in the immuneresponses, point mutations in this gene may not be of immediate clinical impact.However, it may, in theory, change the way the virusreplicates.”Most RNA viruses (including influenza virus)replicate their genome by using the viral enzyme to make copies from the parentRNA. “This enzyme has a weak proof-reading activity, that is, checking ifthe right nucleotides have been incorporated in the genome. Hence, over time,point mutations are bound to happen in the genome of these viruses. In fact, wewould be surprised if they don’t. The majority of these mutations may nothave any significance, either for the virus, or for the host,” saidDalvi.