PROTEINS called interferons are among the latest weapons U.S. Department of Agriculture scientists are using to combat foot and mouth disease (FMD). These proteins kill or stop viruses from growing and reproducing.
Scientists with USDA's Agricultural Research Service (ARS) Foreign Animal Disease Research Unit, located at the Plum Island Animal Disease Center, have demonstrated that interferons can be used to protect animals immediately against FMD infection. This rapid protection gives vaccines time to induce the animal's immune response needed to fight the disease, ARS said.
Interferons consist of three families: type I (alpha-beta), type II (gamma) and type III (lambda). Retired ARS chemist Marvin Grubman discovered that type I interferons are very effective in controlling FMD virus infection. Pigs inoculated with a viral vector containing the gene coding for swine type I interferon and challenged with FMD virus were protected for five days, ARS noted.
To cover the seven-day window it takes for vaccines to start protecting against FMD, Grubman combined interferon types I and II in an antiviral vaccine delivery system, which quickly blocks the virus in pigs. In combination with a vaccine, this patented technology provided thorough protection from day one until the vaccine immune response kicked in seven days later, ARS reported.
These methods work well in pigs, but not in cattle. However, ARS microbiologist Teresa de los Santos, computational biologist James Zhu and Grubman have identified a type III interferon that rapidly protects cattle against FMD virus as early as one day after vaccination, ARS said. In laboratory tests, disease was significantly delayed in animals exposed to FMD virus after previously being treated with bovine type III interferon, compared to a control group that did not receive treatment.
In other experiments, the type III interferon treatment was found to be even more protective in cows that were naturally exposed to FMD, according to de los Santos.