GAINESVILLE, Fla. - A University of Florida researcher has discoveredan unexpected link between the viruses that cause feline and humanAIDS: Cats vaccinated with an experimental strain of the human AIDSvirus appear to be at least as well-protected against the felineversion of the disease as those immunized with the vaccine currentlyused by veterinarians.
The surprise finding may mean cats with feline immunodeficiencyvirus, also known as FIV or feline AIDS, could eventually be treatedeven more effectively using some form of the experimental humanvaccine.
Researcher Janet Yamamoto, a professor at UF's College ofVeterinary Medicine, also theorizes that these emerging relationshipsbetween the two viruses could one day lead to a vaccine for human AIDS.
Results from Yamamoto's research can be previewed in today's (Sept. 8) online issue of the journal AIDS.
FIV is a natural infection of domestic cats that results in animmunodeficiency syndrome resembling HIV infection in humans. Since itsdiscovery in 1987, FIV infection of cats has been used in vaccinestudies as a small-animal model of human AIDS.
"We were the first to demonstrate that you can make aneffective vaccine against a virus in the AIDS family of viruses," saidYamamoto, a co-discoverer of FIV.
Yamamoto holds the patent on the only approved vaccineavailable through veterinarians to protect cats against FIV. Her mostrecent studies have attempted to improve the efficacy of that vaccineby using strains of FIV found in cats in which the disease had notprogressed for some reason over several years.
To determine the extent to which the human and feline AIDSviruses react to each other, and any implications that might exist forvaccine efficacy, Yamamoto began experimenting with long-term,nonprogressive strains of FIV that led to the current commercialvaccine. Now she is working on an HIV vaccine consisting of HIV virusfrom long-term, nonprogressing individuals.
"We purposely made vaccines with strains that weren't virile,"Yamamoto said. "We found that whenever we tried using less virulentstrains of virus, we were able to make a better vaccine."
Yamamoto's team was also surprised to discover that a core protein found in HIV also effectively protects cats against FIV.
"So what does this mean to human AIDS research? The viruses HIVand FIV are from the same viral family," Yamamoto said. "For thatreason, the amino acids that make up the proteins in both viruses sharesome common regions. There appear to be regions of HIV, or variationsof the core protein we used in our studies, that may provide protectionin vaccine form against HIV."
Some compounds made from separate virus strains have beensuccessfully used in vaccines against viruses from the same subfamily,such as smallpox in humans, which is made from cowpox virus, and humanmeasles vaccines for canine distemper in puppies.
"Therefore, protective vaccines based on cross-reactive regionsof AIDS viruses can provide broad immunity, and may be useful againstviruses that are currently evolving in a new host, such as HIVinfection of humans," Yamamoto said.
Alan L. Landay, a professor of immunology and microbiology andassociate department chairman at Rush University Medical Center inChicago called Yamamoto's findings "very exciting."
"This raises a potential whole new area for research in thefield of vaccines that with the current approaches haven't yielded anysuccess to date," said Landay, whose research team is working todevelop novel immune strategies to treat HIV infection. "We need toexplore all the potential options available to us for developing an HIVvaccine."
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