KIDNEY DISEASE:

http://www.cvmbs.colostate.edu/insight/2004/fall2004/cats.htm

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.