Vaccine aims to nip FIP in the bud

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Editor's note: There has been no known transmission of feline enteric coronavirus from domestic cats to humans.

A new contender may soon be entering the ring in the fight against feline infectious peritonitis (FIP). Morris Animal Foundation­–funded researchers from Colorado State University (CSU) are developing an oral vaccine designed to beat the disease to the punch by targeting feline enteric coronavirus (FECV)—the highly contagious and common virus that can mutate randomly into FIP.

“The vaccine attempts that have taken place in the past have focused against FIP, but that’s really not the natural situation,” said Gregg Dean, DVM, PhD, head of the Department of Microbiology, Immunology and Pathology in CSU’s College of Veterinary Medicine and Biomedical Sciences, in an interview with dvm360. “We know that the enteric coronavirus replicates at an amazing rate, doing millions and millions of experiments. Given this opportunity, there’s a chance that it will mutate into the FIP-causing virus—so this is happening inside the cat more than it’s being transmitted between cats. If we could control that replication, we could hopefully prevent the emergence of the mutant.”

Going with the gut

As a first step in understanding what a vaccine would need to do to stimulate a protective immune response against FECV, Dr. Dean and his team studied cats that were naturally infected with the disease, specifically looking at their mucosal immune responses. “The enteric virus is quite limited in where it replicates and that is in the intestinal tract as far as we know,” he explained. “So that’s where the immune response is really critical to understand.”

The vaccine’s design reflects this insight. It will be administered orally and includes the bacteria Lactobacillus acidophilus, a probiotic found in several foods and in the gastrointestinal tract of many animals. “The role of the probiotic is critical,” said Dr. Dean. “Some probiotics stimulate the immune system naturally, and by combining antigens from the feline coronavirus with the natural immune-stimulating activity of the probiotic, we hope to induce a protective and durable immune response.” He explained that probiotic’s effect is amplified by the fact that it is live and replicating. “It’s also producing the antigens—in our case, feline coronavirus antigens—so it’s very economical,” Dr. Dean continued. “We don’t have to use expensive processes to make a lot of antigen. We’re harnessing the natural activity of the bacteria.”

Dr. Dean and his team plan to begin the first efficacy trial for the FECV vaccine this fall. “We’ll deliver the vaccine to cats in a colony environment that has naturally circulating enteric coronavirus. We’ll take new kittens, vaccinate them, and then we’ll see whether they become infected with FECV,” he said. “Nearly every cat, and probably every cat in this colony, gets infected.”

Disease detection

In the meantime, 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 fast. “As we’re moving closer to real, viable treatment possibilities for FIP, having an accurate diagnostic test is going to be an important part of that decision-making process,” he explained. “And an early diagnosis will be important as far as how effective any treatment would be.”

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

It takes a village

With these exciting prospects in feline health on the horizon, Dr. Dean wanted to acknowledge the past and present work of his veterinary colleagues: “There are a large number of people working hard to solve these important problems in cats, and it’s the excellent work of this larger community over time that is getting us all to this point.”

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