A vaccine to prevent FIP in its infancy.

Original article on dvm360.com, published 18.3.2020.

Researchers at Colorado State University want to stop the feline enteric coronavirus before it has a chance to mutate to the feline infectious peritonitis virus.

A new candidate in the fight against feline infectious peritonitis (FIP) may soon enter the scene. Researchers at Colorado State University (CSU), funded by the Morris Animal Foundation, are developing an oral vaccine to beat the disease by targeting feline enteric coronavirus (FECV) - a highly contagious and common virus that can accidentally mutate to FIPV.

“Vaccination attempts that have been made in the past have targeted FIP, but that’s too late,” Gregg Dean, DVM, PhD, chair of the Department of Microbiology, Immunology and Pathology in the College of Veterinary Medicine and Biomedical Sciences, told dvm360. “We know that enteric coronavirus replicates at an amazing rate. So it’s likely that it will mutate into the virus that causes FIP—so there’s more going on inside the cat than is being transmitted between cats. If we can control that replication, we might be able to prevent the mutant from emerging.”

It's all about the gut

As a first step toward understanding what a vaccine would have to do to stimulate a protective immune response against FECV, Dr. Dean and his team studied cats that had been naturally infected with the disease, specifically looking at their mucosal immune responses. “Enteric virus is quite restricted in where it replicates, and that is, as we know, in the intestinal tract,” he explained. “So understanding the immune response at that site is critically important.”

The vaccine design reflects this insight. The vaccine will be administered orally and includes the bacterium Lactobacillus acidophilus, a probiotic found in some foods and in the gastrointestinal tracts of many animals. “The role of probiotics is essential,” said Dr. Dean. “Some probiotics stimulate the immune system naturally, and by combining the antigens from feline coronavirus with the natural immunostimulatory activity of the probiotic, we hope to induce a protective and lasting immune response.” He explained that the probiotic’s effect is enhanced by the fact that it is alive and replicating. “It also produces antigens – in our case, feline coronavirus antigens – so it is very economical,” continued Dr. Dean. “We don’t have to use expensive processes to produce large quantities of antigen. We are using the natural activity of the bacteria.”

Dr. Dean and his team plan to begin the first trials of the FECV vaccine this fall. “We’re going to give the vaccine to cats in a colony environment where enteric coronavirus naturally circulates. We’re going to take new kittens, vaccinate them, and then see if they get FECV,” he said. “Almost every cat, and probably every cat in that colony, is infected.”

Disease recognition

Meanwhile, Dr. Dean is leading another study funded by the Morris Animal Foundation with a different but related goal: to develop a new diagnostic test for FIP that is accessible, inexpensive, and rapid. “As we move closer to real, viable treatment options for FIP, an accurate diagnostic test will be an important part of that decision-making process,” he explained. “Early diagnosis will be important as long as effective treatment is available.”

Instead of focusing on the cat’s immune response or looking for the virus itself, Dr. Dean and his team are looking for specific biomarkers that are unique to FIP infection. They have identified 18 proteins that appear to be common in cats with FIP, and they are in the process of validating them. If the test is successful, all that will be needed is a blood sample from the patient. “We still have a lot of work to do, but it’s a top priority for us,” he said.

We have a lot of work to do

With these exciting prospects for cat health on the horizon, Dr. Dean praised the past and present work of his veterinary colleagues: "There are a lot of people who work hard to solve these important problems for cats, and it is the excellent work of this community that leads us all to a common goal."

Sarah Mouton Dowdy, a former dvm360.com editor, is a freelance writer and editor in Kansas City, Missouri.