Abstract
Haemagglutinin (HA) and neuraminidase (NA) are two vital surface glycoproteins of influenza virus. The HA of H5N6 highly pathogenic avian influenza virus is divided into Major/H5 and Minor/H5, and its NA consists of short stalk NA and full-length stalk NA. The strain combined with Major/H5 and short stalk NA account for 76.8% of all strains, and the proportion was 23.0% matched by Minor/H5 and full-length stalk NA. Our objective was to investigate the influence of HA–NA matching on the biological characteristics and the effects of the epidemic trend of H5N6 on mice and chickens. Four different strains combined with two HAs and two NAs of the represented H5N6 viruses with the fixed six internal segments were rescued and analyzed. Plaque formation, NA activity of infectious particles, and virus growth curve assays, as well as a saliva acid receptor experiment, with mice and chickens were performed. We found that all the strains can replicate well on Madin–Darby canine kidney (MDCK) cells and chicken embryo fibroblasts (CEF) cells, simultaneously, mice and infection group chickens were complete lethal. However, the strain combined with Major/H5 and short stalk N6 formed smaller plaque on MDCK, showed a moderate replication ability in both MDCK and CEF, and exhibited a higher survival rate among the contact group of chickens. Conversely, strains with opposite biological characters which combined with Minor/H5 and short stalk N6 seldom exist in nature. Hence, we drew the conclusion that the appropriate combination of Major/H5 and short stalk N6 occur widely in nature with appropriate biological characteristics for the proliferation and transmission, whereas other combinations of HA and NA had a low proportion and even have not yet been detected.
Highlights
H5N6 avian influenza virus (AIV) was first isolated from mallards in North America, in 1975 (Gu et al, 2011)
Phylogenetic trees revealed that 673HA and 674HA are clustered in clade 2.3.4.4 of H5N6 (Figure 2)
The strains of Major/H5, to which 674HA belongs, that match with short stalk NA, to which 674NA belongs, all of which we named 674-like, have become dominant strains that account for 76.8% (864 of 1,125) of all strains
Summary
H5N6 avian influenza virus (AIV) was first isolated from mallards in North America, in 1975 (Gu et al, 2011). In China, H5N6 first emerged in 2010, and its extensive circulation among both domestic and wild birds ever since has caused significant economic losses (Wu et al, 2015). Despite no evidence that H5N6 has been transmitted to another continent, it has been detected in migratory birds (Li et al, 2017). According to a recent study, H5N6 has replaced H5N1 as a dominant AIV subtype in ducks in southern China (Bi et al, 2016). The viruses could spread to other countries or continents via bird migration (He et al, 2017; Li et al, 2017)
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