Feline enteric coronavirus and feline infectious peritonitis virus – a Dr. Jekyll and Mr. Hyde story

In light of the COVID-19 pandemic, learn how research on feline infectious peritonitis virus could help fight coronavirus infections in people.

As the COVID-19 pandemic rages on, researchers and governments, as well as news organizations, are paying much more attention to coronaviruses and the diseases they cause. This increased attention COVID-19 has brought places a spotlight on feline infectious peritonitis (FIP), a disease veterinarians have been battling for decades. The benign feline coronavirus that turns into the monstrous feline infectious peritonitis virus is a true Jekyll/Hyde story. Despite decades of research, the prognosis is dismal for cats afflicted by FIP. Although the prognosis for affected cats remains grave, new research might change the course of this disease – and help people affected by coronavirus infections, as well.

Feline coronaviruses have a worldwide distribution and affect both domestic and wild cats. Most cats are exposed to feline enteric coronavirus (FECV) and infected at some time in their life. FECV is highly contagious and transmitted easily through saliva or feces. Very few cats show any symptoms and most recover uneventfully without requiring veterinary care.

After years of speculation, it is now clear that FECV can randomly mutate to feline infectious peritonitis virus. While it’s estimated that only 5% to 10% of infected cats develop feline infectious peritonitis, it is 100% fatal. Feline infectious peritonitis is most common in cats under three years of age, with more than 50% of cases in cats under one year of age. A second spike in cases has been noted in  cats over 10 years of age.

At highest risk are cats that live in close proximity to each other, such as cats that live in shelters, where FIP is five to 10 times more prevalent. Certain breeds of cats are predisposed. Although the exact mechanisms underlying genetic susceptibility to the disease are unknown, they are suspected given breed incidence and evidence that siblings of cats that succumb to FIP may be at increased risk for the same disease, even if living apart.

FIP is difficult to diagnose, and effective treatments currently are not available. However, two newly funded studies underway at Colorado State University, hope to change that paradigm.

Under the leadership of Dr. Gregg Dean, Professor and Head of the Department of Microbiology, Immunology and Pathology in CSU’s College of Veterinary Medicine and Biomedical Sciences, a research team is constructing an oral vaccine for feline enteric coronavirus. If successful, the vaccine will control pervasive FECV infection in shelters and other multi-cat environments, while also protecting individual cats against FIP.

“For years, we have tried, unsuccessfully, to vaccinate against feline infectious peritonitis, but we may have been targeting the wrong point in time,” said Dr. Dean. “Our strategy now is to eliminate FECV, the mild-mannered Dr. Jekyll form, if you will, before it can become the deadly Mr. Hyde.”

The team’s vaccine design will exploit the bacteria Lactobacillus acidophilus, familiar to most as a probiotic and inhabitant of the gastrointestinal tract. The vaccine uses specific FECV antigens to generate protective antibodies against infection by FECV.

The vaccine is designed to be given orally, rather than injected, for several reasons. Oral vaccines are preferred by cats and their owners. Oral vaccination avoids the risk of injection site sarcoma. And, since exposure occurs at the mucosal surface of the intestinal tract, an oral vaccine would hopefully stimulate a more vigorous response at the point of infection, as opposed to an injectable vaccine that might be ineffective at stimulating an adequate mucosal immune response.

Dr. Dean’s team also is tackling another elusive goal – developing an accurate diagnostic test for feline infectious peritonitis. The test would use a blood sample to look for biomarkers consistent with disease. His team has identified 18 proteins, among thousands, that appear to be common in cats with the disease. The researchers aim is to evaluate the proteins as markers for FIP and determine which ones can be detected easily and developed into a diagnostic test.

A final exciting development is that Dr. Dean’s work on a feline coronavirus vaccine has the potential to inform work on a vaccine for the current coronavirus pandemic. The research team has now focused their attention – and their expertise – on SARS-CoV-2.

“Our work on a feline coronavirus vaccine has allowed us to quickly engage in work to assess the same approach against SARS-CoV-2,” said Dr. Dean. “I strongly believe the lessons learned over years of work by many investigators to develop a vaccine for cats can be directly applied to the current pandemic.”

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