Journal of Associated Medical Sciences (Jan 2016)
Molecular change of hemagglutinin and neuraminidase of 2009 pandemic influenza virus H1N1 in Thailand, 2009-2011
Abstract
Background: The 2009 pandemic influenza virus A (H1N1) caused the global pandemic disease since the first outbreak reported in April 2009. HA and NA genes of influenza virus have the frequent antigenic variation resulted from immune response and drug. Objective: To analyze HA and NA genes from 34 viral isolates circulating during 2009-2011 in Thailand to elucidate the genetic drift of these genes. Methods: A total of 34 samples of viruses were derived from individuals with influenza-like illness (ILI) in each epidemic wave from different regional areas of Thailand. Nucleotide sequences of HA and NA of viruses from each epidemic wave were analyzed and compared with the vaccine strain. Phylogenetic tree was constructed from the concatenated HA and NA nucleotide sequences of viruses isolated in this work. HI titer of the virus isolated from each epidemic wave was also determined with a reference human serum. Result: Nucleotide and amino acid sequences analysis revealed that antigenic drift from vaccine strain of both genes has been occurred in the antigenic site since the first epidemic wave in Thailand. The increasing of mutation in the antigenic site could be observed in virus isolated from the 4th epidemic wave. However, no any amino acid differences could be found in receptor binding site and glycosylation site within HA of most virus isolates comparing to the vaccine strain according to HI titer. Additionally, change in amino acid sequence was not occurred in the drug binding site of NA. Phylogenetic tree analysis could classify viruses into closely related but distinct clusters. Conclusion: Viruses were different between early pandemic and the 4th epidemic wave. Therefore, surveillance of the antigenic drift of 2009 pandemic influenza virus A (H1N1) should be continuously followed up for the consideration of vaccine update and drug treatment in Thailand. Bull Chiang Mai Assoc Med Sci 2016; 49(1): 36-52. Doi: 10.14456/jams.2016.12