Characterization and Genetic Evolution of H6N2 Subtype AIV Isolates from Aquatic Birds

Area of Science:

• Veterinary Virology
• Molecular Epidemiology
• Infectious Disease Ecology

Background:

• Birds are primary reservoirs for avian influenza viruses (AIVs), with wild bird migration facilitating virus spread.
• Jianhu Lake is a critical stopover for migratory birds, increasing the risk of AIV transmission.
• Understanding AIV diversity and host adaptation is crucial for preventing zoonotic spillover.

Purpose of the Study:

• To isolate and characterize avian influenza H6N2 virus strains from migratory birds at Jianhu Lake.
• To investigate the genetic origins and reassortment events of the isolated AIVs.
• To assess the in vitro replication and in vivo pathogenicity of a representative H6N2 strain in mammalian models.

Main Methods:

• Sample collection from 619 avian individuals at Jianhu Lake.
• Isolation and subtyping of avian influenza viruses.
• Whole-genome sequencing and phylogenetic analysis.
• In vitro cell culture replication assays.
• In vivo infection studies using BALB/c mice.

Main Results:

• Four H6N2 AIV strains were isolated from grey herons, Eurasian wigeon, and domestic ducks.
• Genomic analysis indicated the viruses belong to the Eurasian lineage, resulting from complex reassortment.
• The representative strain JH-2-11 replicated efficiently in human and animal cell lines.
• JH-2-11 infected mice, causing respiratory lesions and weight loss without mortality or extrapulmonary spread.

Conclusions:

• The isolated H6N2 AIVs from Jianhu Lake are of Eurasian origin and show evidence of extensive genetic reassortment.
• The H6N2 strain JH-2-11 demonstrates the capacity for mammalian cell replication and in vivo infection without prior adaptation.
• These findings highlight the potential for AIVs to adapt to mammals and underscore the need for continuous epidemiological surveillance in wild bird populations.