Every time Dr. Sarah Caddy drives to her lab at the Baker Institute for Animal Health, she passes Parvo Drive, right next to the institute. It's a fitting welcome. "Parvo" refers to canine parvovirus, which causes a highly contagious, dangerous disease that researchers at the institute were the first to identify.
Caddy is continuing the institute's 75 years of innovative collaborative research and pioneering discoveries.
"It is exciting to work in a place that is so rich in veterinary research history," said Caddy, assistant professor at the Baker Institute in the Department of Microbiology and Immunology in the College of Veterinary Medicine. "I always enjoy having visitors and telling them stories of the things that have been uncovered in this very institute."
Since Caddy arrived in Ithaca from her native U.K. in 2022, she has focused on understanding how antibodies work against viruses.
"A lot is still not known about how these incredible little proteins work," she said, "even though they are pivotal to protecting animals from different virus infections."
She is especially interested in maternal antibodies, which are passed from mother to infant through the placenta or milk in all mammalian species. During the high-risk period following birth, these antibodies provide essential protection to babies whose own immune systems are immature and not ready to combat the microbes that might otherwise infect them.
Caddy, who earned her veterinary degree from the University of Cambridge and has a Ph.D. in virology, studies this topic primarily in mice, humans and dogs.
"And this is where the legacy of the Baker Institute really comes into play," she said.
Research with deep roots at Baker
In 1958, Dr. James A. Baker, Ph.D. '38, D.V.M. '40, was a co-author on one of the first published papers confirming that dogs transfer antibodies to their puppies. In this study, the antibodies protected puppies against canine distemper virus, at that time a common deadly disease. This discovery came only a few years after the Cornell Research Laboratory for Diseases of Dogs had been dedicated, in 1951, as a division of the newly founded Veterinary Virus Research Institute. The institute was later renamed in Baker's honor.
Dr. James A. Baker, Ph.D. '38, D.V.M. '40, pictured here in 1966, is the founding director and namesake of the Baker Institute for Animal Health at the College of Veterinary Medicine.
Baker and his colleagues noted a finding directly relevant to Caddy's research today: Puppies develop immunity to a disease via a vaccine only after they lose the protection conveyed from their mother and become susceptible to distemper. But when would be the right time to vaccinate?
Based on the consistent decline of maternal immunity as the puppies grow, Baker and his colleagues developed a two-dimensional diagram called a nomograph. With information from the pregnant dog's serum titer, the nomograph predicted when unborn puppies could be immunized "and thereby make available maximum protection from vaccine by vaccination at the earliest possible age," they wrote.
Subsequent work by Leland "Skip" Carmichael, Ph.D. '59 - one of Baker's first graduate students and later the John M. Olin Professor of Virology - and others showed that the vaccine for measles used in humans could be used to immunize young puppies against distemper virus.
"That is now standard practice and has saved thousands upon thousands of puppies from death due to distemper," said Roy Pollock, D.V.M. '78, Ph.D. '81, one of Carmichael's advisees and now chief learning officer at The 6Ds Company.
In 1978, Pollock teamed up with Carmichael and virologist Max Appel, Ph.D. '67, now professor emeritus, to meet a new mysterious challenge confronting dogs: a rapidly spreading disease that caused vomiting, severe diarrhea and death. Thanks to the Baker Institute's state-of-the-art facilities and faculty expertise, Pollock said, they were able to make quick headway in identifying parvovirus as a never-before-seen virus in dogs. Within three years, they had followed up with a diagnostic test (which remained the standard for many years), a vaccine and a groundbreaking 1982 paper.
"It was still very soon after the discovery of canine parvovirus and there was much to learn about the transmission, pathophysiology and development of immunity, both natural and by immunization," Pollock said. He and co-author Carmichael showed that maternal antibodies alone were sufficient to confer immunity against parvovirus; once a dog had been infected, it remained immune for a long time, and mothers passed on their immunity to their pups.
Dr. Sarah Caddy, left, assistant professor at the Baker Institute for Animal Health in the Department of Microbiology and Immunology in the College of Veterinary Medicine, collaborates with colleagues from Zambia, on human maternal antibodies that protect babies from rotovirus.
Colin Parrish, Ph.D. '84, the current John M. Olin Professor of Virology, completed his graduate work with Carmichael and went on to identify the cause of the canine parvovirus pandemic: a mutant version of the feline panleukopenia virus.
"Our work has shown that the canine parvovirus in the 1970s emerged as a variant of a virus of cats - feline panleukopenia virus - and spread as a pandemic in dogs during 1978," Parrish said. "We have shown that dogs were able to be infected because the virus gained the ability to bind and infect the cells of dogs, and that it continues to evolve in both cats and dogs to create variants with altered properties."
Continuing research on canine viruses
Caddy continues the Baker Institute's long history of research on canine viruses and the role of maternal immunity.
She is now studying the differences between the maternal antibodies in dogs that are transferred shortly after birth through the colostrum and the less frequent ones transferred through the placenta before birth. Caddy's team is collecting samples during canine cesarian sections at the Cornell University Hospital for Animals to examine the role of maternal antibodies transferred through the placenta.
Virologist Dr. Max Appel, Ph.D. '67, shown here in 1988 and now professor emeritus, and his colleagues identified parovirus as a never-before-seen virus in dogs.
Comparing titers from the mother and from the puppy's cord blood, Caddy said, "we've already found some interesting differences in the biology." They've found that about 5% of the maternal antibodies pass through the placenta, compared to nearly 100% in humans.
In future work, Caddy hopes to take a closer look at the role of the placental transfer in dogs to understand the source of some of these differences. "We're really hoping to take it a step further to understand the actual biology underpinning this transfer," Caddy said. "And once we know more about it, can we enhance it?"
Her research builds on the work of Carmichael and Baker, as she studies a diverse population of client-owned dogs.
"It's wonderful to be continuing and extending that research by using a new array of antibody tests that examine all aspects of antibody structure and function," Caddy said. "We're a unique institution, and I appreciate the opportunity to cover all species, from pets to humans, from domestic animals down to mice."
Olivia Hall is a freelance writer for the Baker Institute for Animal Health.
