Insight

Fall 2004

Welcome

Veterinarians have long been stumped by the high prevalence of kidney disease in cats. While some cases are tied to specific illness such as arterial hypertension, pyelonephritis (infections), or toxicities, most causes of chronic renal failure in cats remain undetermined. So when feline vaccine research at Colorado State University showed some interesting anomalies in feline blood samples, researchers were intrigued and began to ask some questions that are in the process of being answered.

“Cats commonly go into chronic kidney failure, especially older cats, and we’ve been asking ourselves for a long time, what goes wrong, what kills these kidneys over time?” said Dr. Michael Lappin, Professor in the Department of Clinical Sciences and the Kenneth W. Smith Professor in Small Animal Clinical Medicine. “Most cats that die of kidney failure without a known cause have infiltrations of lymphocytes and plasma cells in the kidney tissues. These cells can indicate an immune reaction.”

In the 1970s, it was discovered that a cell line derived from a cat kidney – the Crandall-Reese feline kidney (CRFK) cell line – could be used to grow feline viruses like feline herpesvirus1 (FHV-1), calicivirus, and panleukopenia. Some vaccine manufacturers began using the CRFK cell line to grow the viruses and then used them in a combined vaccine (FVRCP vaccine). In general, veterinarians administer the FVRCP vaccines to cats approximately three times as kittens with a booster at one year and, after that, boosters every one to three years. The use of the FVRCP vaccination program has helped save many feline lives by inducing great immunity to these three dangerous viruses.

During the course of a Colorado State University and Heska Corporation collaborative study to determine if blood tests could be used to assess the need for vaccines, researchers made an interesting discovery that related to the commonly used FVRCP vaccine.

“The vaccine companies are doing a great job making pure and effi cacious vaccines,” said Dr. Lappin. “However, when FVRCP vaccines are made, each dose is contaminated with just a little bit of cell culture. What we discovered recently was that cats not only develop antibodies to the viruses in the vaccine, which is our intent, but they also develop antibodies to the cell culture – a culture based on a feline kidney cell line. And that’s where we have to begin to ask some very intriguing questions. In particular, is it possible that overvaccination induces antibodies that are associated with immune-mediated feline kidney disease?”

An early proof concept study conducted in Dr. Lappin’s laboratory as a collaboration between Colorado State University and the Heska Corporation showed the development of CRFK antibodies in cats after administration of injectable FVRCP vaccines. In some cats, these antibodies reacted with cat kidney cell extracts as well. But just because cats are producing antibodies to the CRFK proteins and cat kidney cell extracts does not mean those antibodies are causing illnesses or the deterioration of a cat’s kidney health. Dr. Lappin said much work remains to be done before associations like that can be made. In a grant recently funded by the Heska Corporation, a more in-depth approach should begin to provide some answers. Dr. Lappin and Dr. Jacqueline Whittemore will study which feline tissues react with anti-CRFK antibodies; determine the concentrations of CRFK proteins in all commercially available FVRCP vaccines; and determine if the presence of CRFK or feline kidney cell antibodies are associated with the development of particular illnesses in cats including kidney failure, uveitis, pancreatitis, and hyperthyroidism.

Concerns regarding over-vaccination have led the American Association of Feline Practitioners to adjust the vaccine schedule for FVRCP to once every three years after the kitten series and one year booster. However, it is very important for each cat to be treated as an individual. Owners should bring their cats to their veterinarian every year for a health check-up and to determine an optimal vaccination plan. In other studies, Dr. Lappin worked closely with the Heska Corporation to develop a veterinary-market blood test so veterinarians can test patients to see if vaccine boosters are necessary at the time of a cat’s annual check-up rather than just arbitrarily vaccinating.

For additional information on these studies or if you are interested in finding out how you can support Dr. Lappin’s work, contact Dr. Lappin at (970) 221-4535.