Molecular epidemiology and antigenic analyses of influenza A viruses H3N2 in Taiwan

Abstract

The severity of an influenza epidemic season may be influenced not only by variability in the surface glycoproteins, but also by differences in the internal proteins of circulating influenza viruses. To better understand viral antigenic evolution, all eight gene segments from 44 human H3N2 epidemic strains isolated during 2004-2008 in Taiwan were analyzed to provide a profile of protein variability. Comparison of the evolutionary profiles of the HA, NA and PB2 genes of influenza A (H3N2) viruses indicated that they were derived from a group of H3N2 isolates first seen in 2004. However, the PA, M and PB1 genes were derived from a different group of H3N2 isolates from 2004. Tree topology revealed the NP and NS genes could each be segregated into two groups similar to those for the polymerase genes. In addition, new genetic variants occurred during the non-epidemic period and become the dominant strain after one or two seasons. Comparison of evolutionary patterns in consecutive years is necessary to correlate viral genetic changes with antigenic changes as multiple lineages co-circulate.

Phylodynamics and Molecular Evolution of Influenza A Virus Nucleoprotein Genes in Taiwan between 1979 and 2009

“…Phylogenetic analysis demonstrates that at least 2 clusters of H3N2 viruses cocirculated after 2004, but there was no temporal link between the groups because they were equally distributed throughout the study period. Furthermore, our previous report has revealed the co-circulation of multiple distinct groups and frequent intra-subtype reassortment events among them and such evolution plays an important role in antigenic drift [10]. Importantly, it should be noted that in 1980, 3 H1N1 viruses (A/Taiwan/509/1980, A/Taiwan/777/1980, and A/Taiwan/783/1980) grouped into the H3 lineage.…”

“…The tree topology revealed the NP and NS genes could each be segregated into two groups similar to those for the polymerase genes. In addition, new genetic variants occurred during the non-epidemic period and become the dominant strain after one or two seasons [10]. The functional domains of NP have been mapped in the primary structure of the molecule [11].…”

Evolution of the neuraminidase gene of seasonal influenza A and B viruses in Thailand between 2010 and 2015

“…These findings are consistent with previous studies, which reported the overall ω values for the NA genes of 0.30 for seasonal A(H1N1), 0.32 for A(H1N1)pdm09, 0.29 for A(H3N2), and 0.20–0.31 for influenza B virus [3, 51, 54, 57]. The selection pressure of NA of A(H3N2) in German was 0.21, while in Taiwan it was 0.37 [58–59]. Moreover, the findings showed that NA gene had highest a number of amino acid residue under the positive selection.…”

Effect of reassortment on the nucleotide and amino acid changes of human A/H3N2 RNP subunits during 1998–2009

“…No significant change was observed in the rates of the Sydney-like and Fujian-like NP (F 1,8 = 0.40, p ≥ 0.05). A minor reassortment within the Fujian-like RNP segments occurred in [2006][2007]40 and this is illustrated with the Sydney isolates in the phylogenetic trees in Fig. 2 Fig.…”

“…Moreover, the differences in rates of evolution indicate the subunits were evolving independently despite forming a complex, 43 and not linked to the evolution of HA. 24 Although all the RNP subunits in the period 2004-2009 lay within the Fujian-like cluster, a minor reassortment between the internal segments occurred in 2006-2007 40 (Fig. 2).…”