Findings from a new study suggest that when animals catch COVID-19 from humans, new SARS-CoV-2 types may arise.
To evaluate this phenomenon, an interdisciplinary team in the College of Veterinary Medicine and Biomedical Sciences systematically analyzed the mutation types that occur in the virus after infection with cats, dogs, ferrets and hamsters. The study was recently published in ‘PNAS’, the official journal of the National Academy of Sciences.
Confirmed COVID-19 cases in a variety of wild, zoo and domestic animals demonstrate cross-species transmission, a rare event for most viruses.
“SARS-CoV-2, within the scope of coronaviruses, has a very broad species range,” said Laura Bashor, one of the first authors and a doctoral student in the Department of Microbiology, Immunology and Pathology. “In general, many types of viruses cannot infect other species of animals, they have evolved to be very specific.”
“Humans have such a high exposure to so many different animals, which has given the opportunity to expose different species to this virus,” said Eric Gagne, first author and now assistant professor of wildlife disease ecology at the University of Pennsylvania.
The virus’s global reach and spread have given researchers a unique opportunity to investigate the viral evolution of SARS-CoV-2, including in the laboratory of University Distinguished Professor Sue Vandevwood at Colorado State University.
These experts in disease transmission in wild and domestic cats applied their experience in studying sequence analysis and collection of genomes to SARS-CoV-2. Researchers from the Vandevood Lab worked with Assistant Professor Angela Bosco-Loth and Professor Dick Bowen in the Department of Biomedical Sciences, who used their animal modeling expertise to develop a test for SARS-CoV-2 susceptibility of animal species .
Furthermore, key to the findings was a new sequencing technology of viruses at different stages of the study, which is now common for detecting variants in human populations. Mark Stanglin, associate professor in the Department of Microbiology, Immunology, and Pathology, provided computational skills in analyzing biological molecule sequences, known as bioinformatics, for the study.
“We found that there was evolution, we saw selection on the virus, and we saw a lot of variants unfold in the genome sequence of the virus,” Bashor said.
To provide sufficient viral material for study, Bosco-Loth and Bowen cultivated a SARS-CoV-2 human sample in lab-grown cells. Bayshore and Gagne determined that many mutations evolved at each stage of this process, and made up a large percentage of the genetic population.
The virus was then introduced into four domesticated species, and virus samples were collected from their nasal passages after infection.
“In animals, the cell culture forms reverted to the early human type, which indicates that adaptation is probably taking place in the cell culture and environment that those forms were selected for,” Gagne said.
Not all of these mutations within the cell culture transfer the SARS-CoV-2 variant to the new host. Instead, various mutations emerged within the virus shed by living animals.
The initial viral sample in the study was isolated in early 2020. The team observed mutations that have formed widespread SARS-CoV-2 strains in the human population at an accelerated rate throughout the study.
“There were a number of them that we have seen in humans in alpha, beta, delta forms,” said senior author Dr Sue Vandevoude. “There were specific genetic code changes that mimicked what other scientists report in people.”
Contact exposure between two cats exhibiting the SARS-CoV-2 variant can be transmitted with the potential for creating a new strain within the species.
“That’s what we’re seeing in people as well,” Bosco-Lauth said. “Hosts that are really well adapted to support SARS-CoV-2 infection are also very good at allowing these mutations to persist and be passed on.”
Bashor hadn’t anticipated studying SARS-CoV-2 when she came to CSU to begin her doctoral studies during the pandemic. However, it provided a unique opportunity to get off the ground as a graduate student on a “really cool and viable project” in disease ecology and evolution.
When the team began the SARS-CoV-2 study, Gagne was completing his postdoctoral research on cross-species transmission of feline retroviruses in the Vandevood lab. Now an assistant professor, he continues to investigate the SARS-CoV-2 spillover with the Wildlife Future Program at the University of Pennsylvania.
Vande Woude said graduate students and early career scientists such as Bashor and Gagne have made meaningful contributions to SARS-CoV-2 research.
The team is continuing its investigation focusing on cats, as they have shown high susceptibility to COVID-19 spillover from humans and variants of the virus can produce and spread to other cats.
Bashor began analyzing SARS-CoV-2 genome sequences from a large pool of cat species around the world, including tigers, lions and snow leopards. Publicly available data from infected cats may provide additional insights on the adaptability and variability of COVID-19 within and between cat species.
There is no evidence of transmission from cats to humans. But cats remain susceptible to all forms of COVID-19 in the human population.
By understanding viral evolution within cats, the research team may be able to find an answer to the question: What is the future of SARS-CoV-2 for humans and animals.
(Except for the title, this story has not been edited by NDTV staff and is published from a syndicated feed.)