Antigenicity and genetic #properties of an #Eurasian #avian-like #H1N1 swine #influenza virus in #Jiangsu Province, #China

Highlights

• Scientific question: Cross-species transmission of influenza A viruses from swine to humans occurs occasionally because their tracheal epitheliums possess both sialic acid α-2,6-Gal and α-2,3-Gal receptors. In 2011, the first human case of swine influenza virus infection in the mainland of China was detected in Jiangsu Province. Subsequently, the Eurasian avian-like H1N1 swine influenza virus (EAH1N1 SIV) had sporadically crossed the host barrier and infected humans, raising public concern for its pandemic potential.

• Evidence before this study: A/Jiangsu/1/2011 (H1N1v) was first discovered in 2011 and belongs to the G1 genotype. The G4 and G5 genotypes that appeared successively in 2013 are recombinant H1N1 swine influenza viruses. The EAH1N1 SIVs from 2016 to the present are dominated by the G4 genotype, with hemagglutination (HA) and neuraminidase (NA) genes derived from the EAH1N1 SIVs, non-structural protein (NS) genes derived from the triple-origin reassortant swine influenza viruses, and the rest of the internal genes from influenza A (H1N1) pdm09 virus.

• New findings: This study investigated a case of the EAH1N1 SIV infection in a child. This is the first case of the EAH1N1 SIV genotype G4 infection in a child in Jiangsu Province. This virus maintained the genetic properties of the EAH1N1 SIV but differed significantly in HA protein antigens.

• Significance of the study: This new human case of the EAH1N1 SIV infection indicates the pandemic potential of avian influenza viruses.

Abstract

Pigs are vital genetic mixing vessels for human and avian influenza viruses because their tracheal epitheliums possess both sialic acid α-2,6-Gal and α-2,3-Gal receptors. Cross-species transmission of influenza A viruses from swine to humans occurs occasionally. The first case of human infection with the Eurasian avian-like H1N1 swine influenza virus (EAH1N1 SIVs) genotype G4 was detected in Jiangsu Province, China, in February 2023, and backtracking epidemiological investigations did not reveal a clear source of the infection. The hemagglutination (HA) and neuraminidase (NA) amino acid variant sites, antiviral drug susceptibility, and antigenic variation of the isolated A/Jiangsu/27271/2023 (JS/27271/23) virus were analyzed, and we evaluated the protective effect of sera collected from occupationally exposed populations in 2024 against the virus. Compared with the vaccine strain, the nucleotide sequence similarities of JS/27271/23 HA and NA were 96.5 % and 95.2 %, respectively. JS/27271/23 was sensitive to polymerase inhibitors (favipiravir and baloxavir), and the antigenicity of its HA protein was 8-fold different from that of the vaccine strain. The percentage of occupationally exposed population with antibody titers of ≥ 40 against A/Hunan/42443/2015 (HN/42443/15) and A/Jiangsu/1/2011 (JS/1/11) were 7.25 % and 2.25 %, respectively, and the geometric mean titers (GMT) were 6.24 and 5.34, respectively. Out of 400 serum samples examined, none had antibody titers of ≥ 40 against JS/27271/23. This suggests that low serum levels of antibodies to EAH1N1 SIVs in occupationally exposed populations may not provide adequate protection because of significant differences in amino acid sites and antigenicity between this virus and the current vaccine strain of EAH1N1 SIVs. There is no evidence of human-to-human transmission of EAH1N1 SIVs. Therefore, surveillance for EAH1N1 SIVs and the development of new vaccine strains are required.

Source: Biosafety and Health, https://www.sciencedirect.com/science/article/pii/S2590053624001381?via%3Dihub

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