Lychee, a domestic long-hair cat, had feline infectious peritonitis, a feline coronavirus. He was part of a clinical trial at the UC Davis School of Veterinary Medicine that cured him of the disease. Credit: UC Davis
Researchers at the University of California, Davis, have uncovered new details about how a once-deadly coronavirus disease in cats spreads through the immune system. The findings may help scientists better understand long COVID and other long-lasting inflammatory illnesses in people.
The disease, feline infectious peritonitis or FIP, is caused by a form of feline coronavirus that changes inside some cats. If left untreated, it is almost always fatal. While FIP only affects cats, it shares many features with serious coronavirus-related conditions in humans, including severe inflammation that can damage multiple organs, as well as symptoms that can persist or return. For years, the prevailing belief was that the virus behind FIP infected just one type of immune cell. However, this study found it actually infects a much broader range of immune cells.
In their study, published in Veterinary Microbiology, the researchers examined lymph node samples from cats with naturally occurring FIP. They found viral material inside several types of immune cells—including B lymphocytes, which produce antibodies, and T lymphocytes, which help the immune system recognize and eliminate infected cells. They also found evidence that the virus was actively replicating itself inside these immune cells, rather than simply leaving behind harmless fragments.
In people with severe or long-lasting coronavirus illnesses, scientists suspect that the virus may persist in the body or continue to disrupt the immune system. Studying this directly in humans is difficult, because doctors rarely have access to immune tissues, such as lymph nodes. Cats with FIP offer a rare opportunity to study these processes up close.
The researchers also found that traces of the virus could remain in immune cells even after antiviral treatment ended and cats appeared healthy. Because some immune cells can live for years, this lingering infection could help explain long-term immune problems or disease relapse.
Overall, the findings suggest that FIP may serve as a valuable real-world model for understanding how coronaviruses interact with the immune system over time.
Data from UC Davis