Characterization of a reassortant #H3N2 swine #influenza virus with 2009 pandemic internal #genes and enhanced potential for zoonotic #risk

 

Highlights

• A swine influenza virus H3N2 subtype was isolated during epidemiological survey.

• It is a complex and novel reassortant, and acquired accumulation of adaptive mutations.

• Both rescue and parent strains demonstrated efficient replication in mammalian cells.

• Key residues of the H3N2 HA collectively enhance the binding preference for human-type receptor.

• The rescued H3N2 cause significant pulmonary pathological damage in mice.

Abstract

Pigs serve as key "mixing vessels" for influenza A viruses, playing a critical role in cross-species transmission, while the H3N2 subtype represents an important lineage within the swine influenza virus (SIV) family. In this study, a novel reassortant H3N2 SIV strain, designated A/Swine/Jiangsu/YZ07/2024, was isolated from pigs exhibiting clinical symptoms in Northern Jiangsu, China during epidemiological survey. Genetic analysis revealed that the virus is a complex reassortant, with the internal genes (M, NP, PB1, PB2, PA) originated from the 2009 pandemic H1N1 lineage, the NS gene exhibiting a North American triple reassortant origin (human-avian-swine origin), and the HA and NA genes belonging to the human-like lineage. Although neither the rescued virus nor its parental strain could replicate effectively in chicken embryos and chicken cells, both demonstrated efficient replication in mammalian cells, reflected by the much higher polymerase activity in mammalian versus chicken cells. The key residues of HA protein (190D, 225D and 228S) collectively enhanced the binding preference for human-type α-2,6-linked sialic acid receptors, which was confirmed by receptor binding assays. Furthermore, mouse infection experiments using the rescued H3N2 demonstrated efficient viral replication in nasal turbinates and lung tissues, accompanied by significant pulmonary pathological damage. These findings indicate that the YZ07 strain, through the vast reassortment and accumulation of adaptive mutations, has acquired potential zoonotic risk, underscoring the importance of surveillance of swine influenza viruses.

Source: 

Link: https://www.sciencedirect.com/science/article/abs/pii/S0378113526000684?via%3Dihub

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Characterisation of a novel #chicken-derived #H3N3 avian #influenza virus detected in #China in 2023: Pathogenicity and immunogenicity

 

Abstract

The poultry industry faces a constant threat from the mutation and transmission of avian influenza viruses (AIVs). While waterfowl and wild birds are natural hosts of H3N3 AIV, reports of H3N3 infections in chickens are limited. However, in 2023, a decline in egg production among laying hens in the Yancheng Region of Jiangsu Province prompted a study. This research aimed to diagnose the aetiology in laying hens through molecular virological methods and characterise the biological properties of the causative pathogens. An H3N3 AIV subtype strain, A/chicken/China/YC01/2023(H3N3), was isolated from chickens exhibiting lesions. Genome sequencing and analysis revealed a novel genetic makeup: the HA gene originated from an H3N8 AIV, the NA gene from an H10N3 AIV, and the internal genes from an H9N2 AIV, all circulating in China. Chickens experimentally infected with the isolate showed signs of Harderian gland haemorrhage, nasal mucus, tracheal circumferential bleeding, and lung bleeding and localised necrosis. Histopathological examination confirmed nasal mucosal and tracheal inflammation, lung capillary congestion, liver cell damage, and sparse splenic lymphocytes. Viral shedding was significantly higher in the oropharyngeal cavity, peaking 2–6 days post-infection, compared to the cloaca. For the first time, the immunogenicity of a novel chicken-derived H3N3 subtype AIV was assessed in specific pathogen-free chickens. An inactivated vaccine, prepared from the isolated strain, resulted in antibody titres peaking at 9.6 log2 four weeks after immunization. Furthermore, challenges with either the isolated strain or a duck-origin BZ01/2023(H3N3) strain after immunisation did not cause clinical signs or viral shedding on day 4. In conclusion, the isolate H3N3 AIV can replicate in chickens, leading to organ damage and pathogenicity. Crucially, the inactivated vaccine derived from this isolate is highly immunogenic and provides cross-protection against the duck-derived strain.

Source: PLoS One, https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0332213

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