Antigenic Evolution Characteristics and Immunological Evaluation of H9N2 Avian Influenza Viruses from 1994–2019 in China

Abstract

The H9N2 subtype avian influenza viruses (AIVs) have been circulating in China for more than 20 years, attracting more and more attention due to the potential threat of them. At present, vaccination is a common prevention and control strategy in poultry farms, but as virus antigenicity evolves, the immune protection efficiency of vaccines has constantly been challenged. In this study, we downloaded the hemagglutinin (HA) protein sequences of the H9N2 subtype AIVs from 1994 to 2019 in China—with a total of 5138 sequences. The above sequences were analyzed in terms of time and space, and it was found that h9.4.2.5 was the most popular in various regions of China. Furthermore, the prevalence of H9N2 subtype AIVs in China around 2006 was different. The domestic epidemic branch was relatively diversified from 1994 to 2006. After 2006, the epidemic branch each year was h9.4.2.5. We compared the sequences around 2006 as a whole and screened out 15 different amino acid positions. Based on the HA protein of A/chicken/Guangxi/55/2005 (GX55), the abovementioned amino acid mutations were completed. According to the 12-plasmid reverse genetic system, the rescue of the mutant virus was completed using A/PuertoRico/8/1934 (H1N1) (PR8) as the backbone. The cross hemagglutination inhibition test showed that these mutant sites could transform the parental strain from the old to the new antigenic region. Animal experiments indicated that the mutant virus provided significant protection against the virus from the new antigenic region. This study revealed the antigenic evolution of H9N2 subtype AIVs in China. At the same time, it provided an experimental basis for the development of new vaccines.

Genetic evolution analysis of hemagglutinin and neuraminidase genes of H9N2 avian influenza virus in external environment of some areas of Yunnan Province, China from 2020 to 2023

“…The Eurasian branch can be divided into three branches: Y280(BJ/94) - like, G1-like and Y439-like[8]. After the A / Duck / Hong Kong / Y280 / 97 strain was reported in 1997, the strain represented by Y280-like became the dominant type in China[9]. The 20 isolates isolated in Yunnan Province in this study were closely related to the Y280-like branch in the Eurasian branch, belonging to the same branch, which was consistent with the national epidemic situation.…”

Antigenic mapping of the hemagglutinin of the H9 subtype influenza A viruses using sera from Japanese quail ( Coturnix c. japonica )

“…A role of position 180 has been suggested also for the cross-species barrier where the 180V mutation favors the replication of H9N2 in mice ( 47 ). Other studies have attributed antigenic modulation to several HA residues without including position 180 ( 26 , 48 ). The latter is consistent with the idea that additional positions within the HA can modulate the antigenic properties, which is consistent with the findings in this report where eight or nine substitutions were introduced ( Fig.…”

Evolutionary Events Promoted Polymerase Activity of H13N8 Avian Influenza Virus

“…Since first identified in United States turkeys in 1966, H9N2 AIVs have spread widely around the world [ 9 , 10 , 11 ]. H9N2 AIVs are the most prevalent subtypes in China and are endemic in multiple avian species [ 12 , 13 ]. Meanwhile, H9N2 AIVs have acquired the ability to overcome species barriers, resulting in infections in pigs, dogs, and even humans [ 14 ].…”