Evaluation of Rough Brucella Strains as Vaccines for Brucellosis and Pseudorabies in Swine
Brucellosis and pseudorabies lead to abortion in pregnant sows and are perpetuated by feral swine reservoirs. A multivalent oral vaccine for these diseases would improve vaccination and eradication programs worldwide. Previous studies have shown that the rough attenuated Brucella strains RB51 and VTRS1, when administered subcutaneously to swine, stimulate host immune responses, transiently colonize tissues, and provide partial protection against virulent B. suis infection in pregnant sows. A plasmid encoding for the pseudorabies virus glycoprotein D (PRV gD) has also been added to these strains as part of this project. This study evaluates the use of these strains as oral vaccines for swine brucellosis and investigates the ability of these vaccines to colonize lymph nodes and stimulate the production of antibodies against rough Brucella antigens and PRV gD. Orally administered VTRS1 stimulated a higher immune response than RB51 in a shorter period of time, transiently colonized lymph nodes, and did not lead to the production of anti-O-polysaccharide (OPS) antibodies that interfere with brucellosis diagnostic tests. Both RB51 and VTRS1 provided substantial litter protection in orally vaccinated sows challenged with virulent B. suis; however, VTRS1, unlike RB51, also provided partial protection in the sow. These studies support the use of orally administered VTRS1 as an efficacious vaccine for swine brucellosis. The addition of a plasmid encoding for PRV gD to these strains created the multivalent vaccines RB51+gD and VTRS1+gD. Compared to the above strains, the addition of the plasmid did not alter immune response stimulation to rough Brucella antigens and these vaccines were safe when administered to pregnant sows. Swine vaccinated with RB51+gD or VTRS1+gD exhibited low immune responses to the gD antigen and delayed tissue colonization by the vaccine strains. It was found that plasmid addition slowed the growth of the vaccine strains in the laboratory, which may account for the suppressed tissue colonization and immune responses to the PRV gD antigen in swine. Further studies are necessary to evaluate the use of these strains as multivalent vaccines for brucellosis and pseudorabies in swine.
Advisor:Dennis French; Frederick Enright; Philip Elzer
School:Louisiana State University in Shreveport
School Location:USA - Louisiana
Source Type:Master's Thesis
Keywords:veterinary microbiology parasitology medical sciences
Date of Publication:10/13/2004