BLACKSBURG, June 22, 1999--A genetically altered vaccine developed by a researcher in the Virginia-Maryland Regional College of Veterinary Medicine has received the final green light from the United States Department of Agriculture (USDA) and is now being commercially marketed as an agent to prevent pneumonia in pigs.
The vaccine, marketed under the trade name "Actinobacillus Pleuropneumoniae Attenuate Live Culture" (APP-ALC) by Boehringer Engleheim /NOBL Laboratories, is the first avirulent live vaccine ever approved for preventing bacterial respiratory disease in animals, according to microbiologist Thomas Inzana, professor in the college's Department of Biomedical Sciences and Pathobiology. Swine pleuropneumoniae causes millions of dollars in production losses a year and is one of the most significant bacterial respiratory diseases in the swine industry, Inzana says.
"It can really wipe out a non-immune herd," he said, adding that an infection can destroy up to half of the herd and sicken most of the others. It's highly virulent characteristics pose a special threat for modern swine production centers where animals are highly concentrated.
The product development and licensing caps a several-year research effort which was made possible by the dramatic scientific advancements in the field of molecular biology over the past ten years.
Since the days of Pasteur, immunology researchers have known that the best immune response is elicited by natural exposure to the pathogenic organism itself, Inzana explains. Unfortunately, many vaccines evoke an inflammatory response and infection in the people and animals they are designed to protect. Working in the college's Center for Molecular Medicine and Infectious Disease, Inzana and colleagues sought to create a genetically altered live vaccine for swine pleuropneumonia, a major cause of production losses in the swine industry, which is caused by the bacterium Actinobacillus pleuropneumoniae.
Inzana determined that the carbohydrate capsule of the bacterium is required for virulence, but not immunoprotection. In contrast, only live bacteria produce the native toxins required for immunoprotection. By mutating the capsular DNA he was able to select for a stable, nonencapsulated vaccine strain that confers excellent immunity in pigs with minimal side-effects.
He believes the technique can also be used to create vaccines against Pasteurella multocida and P. (Mannheimia) haemolytica, the other agents of "shipping fever" in cattle.
The United States Veterinary Biological Product License granted by USDA can be viewed as a significant step forward in the development of live attenuated vaccines for the treatment of respiratory diseases in animals, Inzana said.
Researcher contact information: Dr. Thomas J. Inzana
Early research was published in Infection & Immunity, Vol. 61, pages 1682-1686,
1993.
email: Tinzana@vt.edu