From bench to farm: a new vaccine for the control of bovine brucellosis

UGALDE JE

Capital Federal

Congreso; Brucellosis 2011-International Research Conference; 2011

Asociación Argentina de Microbiología

Bovine brucellosis remains a serious animal health problem in many developing countries and is responsible for important economical losses throughout the world. To date only two vaccine strains have been extensively used for the control of the disease: the smooth S19 strain and the rough RB51 strain. Because both vaccines have benefits and drawbacks (induction of persistent antibody titers, low protection rate, not suitable for pregnant animals or not genetically defined depending on the vaccine), the scientific community is constantly searching for new and improved vaccines, specifically by identifying novel virulence factors whose inactivation could result in an attenuated strain. We report here the results of two efficacy trials performed in bovines in the years 2006 to 2011 to evaluate the protective capacity of a novel vaccine strain, which we have named Delta-pgm. This vaccine strain is derived from the wild-type 2308 and has a non-marked deletion of the phosphoglucomutase (pgm) gene, which catalyzes the reversible interconversion of glucose-1P to glucose-6P, rendering the bacteria rough and avirulent. The trials were performed over a total of 63 animals, and, one and two doses of Delta-pgm subcutaneously administered were tested in comparison with the standard S19 vaccination. The challenge was performed with a high dose of the virulent 2308 strain applied intramuscularly. Several protection variables were analyzed, including time of gestation, colonization of mothers, prevention of abortion and shedding in milk. Independently of the variable used for the analysis, the results indicate that Delta-pgm confers a significant protection, comparable to the one induced by the S19 strain. Because revaccination with Delta-pgm does not induce persistent antibody titers, we postulate that this novel vaccine could be used in annual revaccination campaigns to boost the immune status of herds prior to the reproductive period