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. 2021 Mar 9:12:628979.
doi: 10.3389/fmicb.2021.628979. eCollection 2021.

Molecular Characteristics, Antigenicity, Pathogenicity, and Zoonotic Potential of a H3N2 Canine Influenza Virus Currently Circulating in South China

Meihua Wu  1   2   3   4   5 , Rongsheng Su  1   3 , Yongxia Gu  1   2   3   4   5 , Yanan Yu  1   2   3   4   5 , Shuo Li  1   2   3   4   5 , Huapeng Sun  1   2   3   4   5 , Liangqi Pan  1   2   3   4   5 , Xinxin Cui  1   2   3   4   5 , Xuhui Zhu  1   2   3   4   5 , Qingzhou Yang  1   2   3   4   5 , Yanwei Liu  1   2   3   4   5 , Fengxiang Xu  1   2   3   4   5 , Mingliang Li  1   2   3   4   5 , Yang Liu  1   2   3   4   5 , Xiaoyun Qu  1   2   3   4   5 , Jie Wu  6 , Ming Liao  1   2   3   4   5 , Hailiang Sun  1   2   3   4   5
Affiliations

Molecular Characteristics, Antigenicity, Pathogenicity, and Zoonotic Potential of a H3N2 Canine Influenza Virus Currently Circulating in South China

Meihua Wu et al. Front Microbiol. .

Abstract

Canine influenza viruses (CIVs) could be a source of influenza viruses which infect humans because canine are important companion pets. To assess the potential risk of H3N2 CIVs currently circulating in southern China to public health, biological characteristics of A/canine/Guangdong/DY1/2019 (CADY1/2019) were detected. CADY1/2019 bound to both avian-type and human-type receptors. CADY1/2019 had a similar pH value for HA protein fusion to human viruses, but its antigenicity was obviously different from those of current human H3N2 influenza viruses (IVs) or the vaccine strains recommended in the North hemisphere. CADY1/2019 effectively replicated in the respiratory tract and was transmitted by physical contact among guinea pigs. Compared to human H3N2 IV, CADY1/2019 exhibited higher replication in MDCK, A549, 3D4/21, ST, and PK15 cells. Sequence analysis indicated that CADY1/2019 is an avian-origin virus, and belongs to the novel clade and has acquired many adaptation mutations to infect other mammals, including human. Taken together, currently circulating H3N2 CIVs have a zoonotic potential, and there is a need for strengthening surveillance and monitoring of their pathogenicity.

Keywords: H3N2 canine influenza virus; HA stability; antigenicity; guinea pig; pathogenicity.

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Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

FIGURE 1
FIGURE 1
Phylogenetic analysis of HA gene of CADY1/2019. Phylogenetic trees for whole gene segments of CADY1/2019 created with 1000 bootstrap replicates using MEGA 7.0 software. Solid red square indicated CADY1/2019 in each phylogenetic tree. Phylogenetic trees of HA genes based on nucleotides (nt) 30–1,730.
FIGURE 2
FIGURE 2
Phylogenetic analysis of NA gene of CADY1/2019. Phylogenetic trees for whole gene segments of CADY1/2019 created with 1000 bootstrap replicates using MEGA 7.0 software. Solid red square indicated CADY1/2019 in each phylogenetic tree. Phylogenetic trees of NA genes based on nt 20–1,429.
FIGURE 3
FIGURE 3
Receptor-binding ability of CADY1/2019 (A) and 47/2020 (B). The binding ability of the viruses to two different biotinylated glycans (α-2, 3-siaylglycopolymer, colored in blue, α-2, 6-siaylglycopolymer, colored in red) were detected. The antibody used for the receptor-binding ability of CADY1/2019 was guinea pig sera anti CADY1/2019. The antibody used for the receptor-binding ability of 47/2020 was a monoclonal antibody against H3 subtype AIV that reacts with 47/2020. Every experiment was conducted twice, expressed as mean ± SD.
FIGURE 4
FIGURE 4
Growth kinetics of viruses in mammalian cells. Excepting MDCK cells (A) were infected with viruses at a MOI of 0.001, HBE (B), A549 (C), 3D4/21 (D), ST (E), and PK-15 cells (F) were inoculated with viruses at a MOI of 0.01. The supernatants of cells were collected at 12, 24, 36, 48, 60, and 72 hpi and titrated in MDCK cells. The experiments were repeated for three times and the viral titer at each time point was expressed as mean ± standard deviation. Statistical analysis was performed using Prism 7.0 software (GraphPad, La Jolla, CA). ∗ indicates P < 0.05, ∗∗ indicates P < 0.01, ∗∗∗ indicates P < 0.001.
FIGURE 5
FIGURE 5
The virus titers in different tissues of guinea pigs in CADY1/2019 inoculation group. Four guinea pigs were inoculated intranasally at a dose of 106 TCID50 of CADY1/2019 or 47/2020 in 300 μL. At 3 dpi, two infected guinea pigs in each virus experimental group were euthanized and turbinates, tracheas and lungs of them were collected for virus titration in MDCK cells. 47/2020 did not replicate in respiratory tissues of guinea pigs.
FIGURE 6
FIGURE 6
Replication and transmission of viruses in guinea pigs. Six guinea pigs were inoculated intranasally at a dose of 106 TCID50 of CADY1/2019 or 47/2020 in 300 μL and were then co-housed with three naïve guinea pigs at 1 dpi. Three guinea pigs were intranasally inoculated with 300 μL PBS as control group. The nasal washes of the guinea pigs were collected at 2, 4, 6, 8, 10 dpi for virus titration in MDCK cells. The sera of guinea pigs were collected at 21 dpi for HI titers detection. (A) The nasal wash titers of CADY1/2019 treatment group. (B) The nasal wash titers of CADY1/2019 contact group. (C) The nasal wash titers of 47/2020 treatment group.
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