Genetic characterization of H5N2 influenza viruses isolated from wild birds in Japan suggests multiple reassortment

Abstract

Low-pathogenic avian influenza viruses (LPAIVs) of the H5 subtype can mutate to highly pathogenic forms, potentially destabilizing the poultry industry. Wild migratory birds are considered a natural reservoir of LPAIVs capable of dispersing both high-and low-pathogenic forms of the virus. Therefore, surveillance and characterization of AIV in wild birds are essential. Here, we report on the isolation and genetic characterization of 10 AIVs of the H5N2 subtype obtained through surveillance in Hokkaido, Japan, during 2009 and 2011. Fullgenome sequencing revealed that the H5 and N2 genes of these isolates are all closely related to each other, belonging to the Eurasian avian-like lineage, but they are unrelated to H5 highly pathogenic strains of clade 2.3.4.4. The internal genes of the isolates were found to be diverse, consistent with our hypothesis that these H5N2 strains have undergone multiple reassortment events. Even though all of the H5N2 isolates were characterized as LPAIV based on the amino acid sequences at the HA cleavage site, this analysis demonstrates a diverse pool of precursors that may seed future outbreaks in poultry and possible human transmissions, suggesting the need for high-quality surveillance.

Phylogenetic study of H5 low pathogenic avian influenza viruses detected in wild birds in Poland in 2010−2015

“…The 141/15-like constellation of PA, NP, and NA was detected in Scottish H5N1 LPAIV, whereas PB1 segment of 10/14 showed a high relationship with the French H5N1, a highly pathogenic virus derived from low pathogenic progenitor as a result of mutation accumulation ( 5 ). Similar results providing evidence of virus spill-over from wild birds to poultry and constant gene flow between different viruses were obtained by other authors as well ( 4 , 15 , 23 ). However, crossing the species barrier by AIV is not restricted only to wild bird-poultry transmission, as AIVs have also proven to be able to transmit and adapt to mammals.…”

“…Molecular and phylogenetic analysis of French H5 strains isolated between 2002 and 2008 from domestic ducks showed high complexity of identified genotypes and presence of uncommon molecular features, such as insertions in PB1 and NS1, and truncation of PB1-F2 protein ( 4 ). Similarly, high heterogeneity of gene pool of H5 AIV isolates from wild birds was demonstrated in Nigeria, South Korea, and Japan ( 2 , 21 , 23 ). Gene exchange between Eurasian, North American, and African lineages was also observed for some isolates ( 2 , 21 ).…”

“…Furthermore, a few recent cases of LPAI outbreaks in poultry recorded in Europe have been caused by viruses derived from wild birds ( 10 , 12 , 20 ). Studies characterising the viruses from both wild birds and poultry have shown constant gene flow between various subtypes ( 4 , 15 , 23 ). Molecular and phylogenetic analysis of French H5 strains isolated between 2002 and 2008 from domestic ducks showed high complexity of identified genotypes and presence of uncommon molecular features, such as insertions in PB1 and NS1, and truncation of PB1-F2 protein ( 4 ).…”

Genetic characterization of an avian H4N6 influenza virus isolated from the Izumi plain, Japan

“…Japan is a known part of the East Asia/Australian flyway, which has an area that overlaps with the Pacific and Mississippi America flyways . Therefore, several avian influenza viruses reassorted with multiple lineages have been isolated in Japan .…”