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Title: Immuogenicity and safety of a natural rough mutant of Brucella suis as a vaccine for swine

item STOFFREGEN, WILLIAM - Former ARS Employee
item Johnson, Charles
item Olsen, Steven

Submitted to: Research in Veterinary Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/8/2013
Publication Date: 8/18/2013
Citation: Stoffregen, W.C., Johnson, C.S., Olsen, S.C. 2013. Immunogenicity and safety of a natural rough mutant of Brucella suis as a vaccine for swine. Research in Veterinary Science. 95(2013):251-258.

Interpretive Summary: Brucella suis is an intracellular pathogen that causes reproductive losses in swine and which also causes zoonotic infections in people. Regulatory programs in domestic livestock, which include vaccination of livestock, are the most cost-efficient way to control Brucella suis and prevent human infection. The persistence of brucellosis in feral swine may pose a threat for reintroduction of brucellosis to swine or cattle in the United States. In this paper, we evaluated the immunity induced by a new rough B. suis vaccine, strain 353-1. This vaccine strain induced protective immune responses without inducing antibody responses which will cause false positive results on surveillance tests. The vaccine was safe, was not shed from vaccinated animals, and was cleared by 10 to 12 weeks after vaccination. This data will be of interest to regulatory personnel, people with responsibilities for management of brucellosis in wildlife or domestic livestock, livestock owners, and other parties with interests regarding brucellosis management.

Technical Abstract: The objective of the current study was to evaluate the safety, immunogenicity and clearance of the natural rough mutant of Brucella suis strain 353-1 (353-1) as a vaccine in domestic swine. In three studies encompassing 155 animals, pigs were inoculated with 353-1 by conjunctival (5 x 10**7 CFU), parenteral (1.8-2.0 x 10**10 CFU), or oral routes (5 x 10**11 CFU). Clearance, tissue distribution, and pathology of the vaccine strain was determined by periodic blood culture, collection of tissues at periodic necropsy times after vaccination, and histologic evaluation of tissue samples. The potential for shedding from vaccinates was determined by serologic and microbiologic evaluation of samples from co-housed sentinel animals. The B. suis 353-1 strain was nonpathogenic and cleared from most parenteral or oral vaccinates by 10 to 12 weeks after vaccination. The vaccine strain appears to be stable as all isolates recovered from vaccinates retained their rough phenotype. Parenteral and oral vaccination induced significant humoral responses, peripheral blood mononuclear cell proliferation, and interferon-gamma (IFN-gamma) production after inoculation when compared to responses of control pigs. The vaccine strain did not appear to be shed as co-housed sentinel animals demonstrated no serologic or microbiologic evidence of lateral transmission. Our data demonstrates that B. suis 353-1 is a stable, rough mutant that does not induce adverse clinical effects or tissue localization in vaccinated swine. The strain also induces significant humoral and cellular immune response after oral or parenteral vaccination of swine.