Isolation and characterization of an avian-origin H3N8 canine influenza virus from a dog in eastern China

Development and application of a triplex real-time PCR assay for the detection of H3, H4, and H5 subtypes of avian influenza virus

Avian influenza virus (AIV) poses a significant threat to the poultry industry and public health. Among the diverse AIV subtypes, H3, H4, and H5 are frequently detected in waterfowl and live poultry markets (LPM). The expeditious and precise identification of these subtypes is imperative in impeding the dissemination of the disease. In this study, we have developed a triplex real-time PCR assay endowed with the capacity to simultaneously discriminate AIV subtypes H3, H4, and H5. This method showcases remarkable specificity, selectively amplifying H3, H4, and H5 AIV subtypes sans any cross-reactivity with other subtypes or common avian pathogens. Furthermore, this method exhibits high sensitivity, with a detection threshold of 2.1 × 102 copies/μL for H3, H4, and H5 AIV subtypes. Additionally, the assay demonstrates reproducibility, as evidenced by intra- and interassay variability, with a coefficient of variation below 1.5%. A total of 338 cloacal swabs were collected from LPM to evaluate the performance of our assay. The obtained results evinced a high level of concordance with the sequencing data. In summary, our study has developed a triplex real-time PCR method that can be employed in laboratory-based testing and surveillance of AIV. This assay holds promise in augmenting our ability to detect and monitor AIV subtypes, thereby facilitating timely interventions and safeguarding both the poultry industry and public health.

A multiplex real-time RT-PCR assay for the detection of H1, H2 and H3 subtype avian influenza viruses

Avian influenza viruses (AIVs) are influenza A viruses, of which subtypes H1, H2 and H3 are highly transmissible in poultry and have the risk of transmission to human as well. It is important to establish an accurate, sensitive and convenient means of virus detection. In this study, we developed a multiplex real-time RT-PCR assay based on conserved sequences of the virus hemagglutinin and matrix, and designed primers and probes for the simultaneous and rapid detection of AIV subtypes H1, H2 and H3. We used different subtypes of AIVs and other avian respiratory viruses for evaluation of the specificity of this method. The results showed good sensitivity, specificity and reproducibility. The detection limit was 10-100 copies per reaction. The method also achieved good concordance with the virus isolation method when compared to 81 poultry samples evaluated. It provides a new method for detecting mixed infections of AIVs.

H3N8 subtype avian influenza virus originated from wild birds exhibited dual receptor-binding profiles

We present the phylogeny, receptor binding property, growth in mammal cells and pathogenicity in mammal model of H3N8 viruses, which were isolated from wild birds in China. The human receptor preference and efficient replication in mice without prior adaption highlight that the H3N8 virus possesses the public threat potential.

Domestic poultry are not susceptible to avian-origin H3N2 subtype canine influenza A virus

At present, avian-origin H3N2 subtype canine influenza virus (H3N2 CIV) is prevalent in East Asian and North American countries. The host tropism of H3N2 CIV to mammals, including mice, guinea pigs, ferrets, and pigs, has been evaluated. However, it has not previously been determined whether avian-origin H3N2 CIV can be transmitted back to birds. In China, ducks, chickens, geese, pigeons, and quails are economically important domestic poultry that are susceptible to numerous subtypes of influenza A virus. These poultry occasionally or frequently come into contact with dogs. In this study, the infectivity of the first- and last-isolated Chinese H3N2 CIV strains in these poultry species was evaluated, and oropharyngeal and cloacal swabs of these animals were negative for virus, as determined by specific pathogen-free (SPF) chicken egg inoculation and real-time RT-qPCR assays. Clinical signs and gross lesions were not observed in any of these species, and seroconversion also did not occur. The results showed that all these avian species were unsusceptible to the first- and last-isolated H3N2 CIVs, indicating unidirectional evolution of the mammalian host tropism of H3N2 CIV.

Adaptation of Two Wild Bird-Origin H3N8 Avian Influenza Viruses to Mammalian Hosts

Wild birds play an important role in the emergence, evolution, and spread of zoonotic avian influenza viruses (AIVs). However, there are few studies on the cross-species transmission of the H3N8 AIV originating from wild birds. In this study, we investigated the transmissibility and pathogenicity of two H3N8 low pathogenic avian influenza viruses (LPAIVs) isolated from wild birds, GZA1 and XJ47, to mammals. The HA genes of both strains belonged to Eurasian isolates, while the other genes were derived from a variety of other subtypes of AIVs. Both strains can infect specific-pathogen-free (SPF) chickens, BALB/c mice, and guinea pigs. The XJ47 strain spread horizontally in SPF chickens and guinea pigs. The GZA1 strain did not spread horizontally but caused higher weight loss and mild lung inflammation in mice. P12-GZA1- and P12-XJ47-adapted strains obtained after 12 passages in the lung of mice showed enhanced pathogenicity in mice, which led to obvious clinical symptoms, lung inflammation, and 100% death. Both adapted strains have the reported mutation T97I in the PA, and the reported mutation D701N in PB2 has been found in the P12-GZA1-adapted strain. This study provides an important scientific basis for the continuous monitoring of wild AIVs and the mechanism underlying AIV cross-species transmission.