A recent Virology Journal study evaluates cross-species transmission of newly emerged severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants between humans and poultry species.
Study: Emerging SARS-CoV-2 variants of concern potentially expand host range to chickens: insights from AXL, NRP1 and ACE2 receptors. Image Credit: MadisonRae / Shutterstock.com
The rapid spread of SARS-CoV-2 resulted in the coronavirus disease 2019 (COVID-19) pandemic, which has claimed almost seven million lives worldwide. Genomic mutations of SARS-CoV-2 have led to the emergence of new SARS-CoV-2 variants, several of which have been categorized as variants of interest (VOIs) and variants of concern (VOCs). As compared to SARS-CoV-2 VOIs, VOCs are more virulent and can escape the immunity induced through COVID-19 vaccination or natural infection.
Various animals in close contact with humans have been found to be infected with SARS-CoV-2, which could be due to mutations in the spike (S) protein of the virus and host receptors. Several studies have confirmed the ability of the receptor binding domain (RBD) of the SARS-CoV-2 S protein to interact with the angiotensin-converting enzyme 2 (ACE 2), including those found in several species, such as horses, monkeys, and sheep.
At the start of the pandemic, the ancestral SARS-CoV-2 strain was not able to infect ordinary laboratory mouse models due to differences in mouse and human ACE2 receptors. Comparatively, the SARS-CoV-2 Beta and Omicron variants successfully infected laboratory mice through intranasal instillation. Multiple studies have shown that SARS-CoV-2 VOCs have acquired cross-species infectivity due to mutations.
Currently, only the Gammacoronavirus of the coronavirus family can infect chicken and cause infectious bronchitis. Like mice, chickens were less susceptible to the original strain of SARS-CoV-2. However, no studies have evaluated the potential of SARS-CoV-2 VOC transmission in poultry such as chickens, ducks, turkeys, quail, and geese.
In both experimental and natural infection settings, poultry are considered unlikely intermediate hosts of SARS-CoV-2 VOCs. Nevertheless, the rapid evolution of SARS-CoV-2 has indicated an increased transmission capacity of this virus. Thus, it is important to understand whether continuous mutation of SARS-CoV-2 will enable poultry to become an intermediate host.
About the study
The current study analyzed the possibility of SARS-CoV-2 VOC transmission in chickens. More specifically, the differences in key amino acid residues of neuropilin 1 (NRP1), tyrosine kinase receptor UFO (AXL), and ACE2 receptors between humans, hamsters, rhesus, ferrets, mice, chickens, and mink were compared. The potential of these receptor proteins to bind with SARS-CoV-2 was also assessed.
The FASTA sequences of NRP1, AXL, and ACE2 receptors of the aforementioned species and the SARS-CoV-2 Wuhan-Hu-1, Delta, and Omicron strains were obtained from GenBank.
The protein sequence alignment and interspecific protein modeling of the amino acid sequences of AXL and NRP1 predicted the likelihood of chickens being intermediate hosts of SARS-CoV-2 VOCs.
Both AXL and ACE2 receptors in chickens were the most likely binding sites for emerging SARS-CoV-2 VOCs, thus indicating the potential role of these two sites to establish intracellular infection in chickens. However, NRP1 was less likely to become a potential target for SARS-CoV-2 invasion in chickens.
Recent studies have shown that some members of the coronavirus family, including Betacoronavirus, can infect a wide range of hosts, including humans, dogs, and cattle. This is due to high sequence consistency between species that could lead to cross-species transmission among these viruses. Compared to the SARS-CoV-2 Wuhan-Hu-1 S protein, both Delta and Omicron variants contain heavy mutations that could aid their altered susceptibility towards chicken.
Scientists are currently conducting experimental studies and monitoring research to better understand the susceptibility of chicken to infection with SARS-CoV-2 VOCs.
The current study provides important insights into human-animal transmission and reveals that chickens could be new intermediate hosts for SARS-CoV-2 VOCs. Both the AXL and ACE2 receptors of chickens were identified as potential targets for emerging SARS-CoV-2 VOCs; however, more research is required to analyze other host factors for SARS-CoV-2.
Since poultry are globally distributed at a large scale, the possibility of these animals getting infected with SARS-CoV-2 is a significant threat to public health. The chickens-to-human or human-to-chickens cross-species transmission could lead to another epidemic in humans. Therefore, scientists and policymakers must analyze the findings of the current study and formulate effective measures to prevent such occurrences.
- Lei, M., Ma, Y., Chen, H., et al. (2023) Emerging SARS-CoV-2 variants of concern potentially expand host range to chickens: insights from AXL, NRP1 and ACE2 receptors. Virology Journal, 20(196). doi:10.1186/s12985-023-02123-x