HMN 2025: How Genetic variety highlights rising risk of H9N2 avian influenza

A brand new study published in Nature Microbiology has uncovered vital genetic and antigenic variety amongst H9N2 avian influenza viruses (AIVs) circulating in poultry throughout China, highlighting the rising public well being danger posed by H9N2 AIVs.

Although H9N2—first recognized in China in 1994—has been focused by ongoing vaccination methods, it has remained the dominant subtype in poultry. Its persistence, together with rising reviews of human infections lately, has change into a rising public well being concern.

Previously, the molecular foundation for the virus’s cross-species transmission and zoonotic potential remained largely unclear. Now, nevertheless, a collaborative workforce led by Prof. Bi Yuhai and Prof. George F. Gao (Gao Fu) from the Institute of Microbiology of the Chinese Academy of Sciences, along with Prof. Shi Weifeng of Ruijin Hospital on the Shanghai Jiao Tong University School of Medicine, has carried out a complete investigation into the virus’s genetic evolution, antigenic variability, and adaptive mutations.

Their findings provide essential insights in regards to the virus’s molecular mechanism for mammalian adaptation and evasion of human MxA gene-mediated innate immune responses.

Since 2014, Prof. BI Yuhai has organized groups from the Center for Influenza Research and Early-warning (CASCIRE) to conduct steady surveillance and early warning of AIVs in China and study cross-species transmission mechanisms of AIVs. Surveillance in dwell poultry markets from 2019 to 2023 revealed that the A/rooster/Beijing/1/94 (BJ94) lineage of H9N2 AIVs has persistently dominated in poultry.

To higher perceive its evolutionary trajectory, the workforce developed a novel clade classification system for BJ94 viruses based mostly on genetic distances and phylogenetic relationships. They additionally launched a web-based classification platform to allow world researchers to trace and study H9 AIV evolution.

Using this framework, they recognized ten hemagglutinin (HA) sub-subclades at present co-circulating amongst poultry, every exhibiting distinct antigenic variations. These variations might clarify why the prevailing vaccines have been unable to curb the epidemic of H9N2 AIVs.

Additionally, the researchers discovered a rising prevalence of key mutations related to elevated infectivity and pathogenicity in mammals. Between 2021 and 2023, 99.46% of H9N2 isolates carried the HA-L226 mutation linked to human receptor binding; 96.17% contained the NP-N52 mutation related to resistance to the human MxA antiviral protein; and 32.61% had the PB2-V627 mutation recognized to reinforce polymerase exercise in human cells.

Experiments demonstrated that strains harboring these mutations preferentially sure to human-type receptors, replicated effectively in human cells, and had been able to direct contact and aerosol transmission in guinea pigs and ferrets—key indicators of zoonotic potential.

These outcomes spotlight the heightened zoonotic dangers of H9N2 AIVs. This study underscores the pressing want for enhanced surveillance, up to date vaccine methods, and a deeper understanding of avian influenza virus evolution to mitigate the rising risk of H9N2 to public well being.