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1 Department of Veterinary Pathobiology, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, 4467 TAMU, College Station, Texas 77843-4467, USA
2 Department of Molecular and Cellular Medicine, Texas A&M Health Science Center, College of Medicine, 440 Reynolds Medical Building, College Station, Texas 77843-1114, USA
3 Department of Veterinary Science, Louisiana State University Agricultural Center, Louisiana State University, Baton Rouge, Louisiana 70803, USA
4 Corresponding author (email: aarenas{at}cvm.tamu.edu)
ABSTRACT:
Brucellosis is an important zoonotic disease of nearly worldwide distribution. The occurrence of the infection in humans is largely dependent on the prevalence of brucellosis in animal reservoirs, including wildlife. The current vaccine used for cattle Brucella abortus strain RB51, has proven ineffective in protecting bison (Bison bison) and elk (Cervus nelsoni) from infection and abortion. To test possible improvements in vaccine efficacy, a novel approach of immunization was examined from April 2004 to November 2006 using alginate composite microspheres containing a nonimmunogenic, eggshell-precursor protein of the parasite Fasciola hepatica (Vitelline protein B, VpB) to deliver live vaccine strain RB51. Red deer (Cervus elaphus), used as a model for elk, were vaccinated orally (PO) or subcutaneously (SC) with 1.5x1010 viable organisms per animal. Humoral responses postvaccination (immunoglobulin G [IgG] levels), assessed at different time points, indicated that capsules containing live RB51 elicited an anti-Brucella specific IgG response. Furthermore, the encapsulated vaccine elicited a cell-mediated response that the nonencapsulated vaccinates failed to produce. Finally, red deer were challenged with B. abortus strain 19 by conjunctival exposure. Only animals that received encapsulated RB51 vaccine by either route exhibited a significant reduction in bacterial counts in their spleens. These data suggest that alginate-VpB microspheres provide a method to enhance the RB51 vaccine performance in elk.
Key words: Brucella, elk, microencapsulation, vaccines, Vitelline protein B.
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