ARS | Publication request: Bordetella bronchiseptica Bvg Phase-Dependent Contribution to Colonization, Transmission, and Immune Responses in Pigs

Submitted to: American Society for Microbiology Meeting
Publication Type: Abstract Only
Publication Acceptance Date: February 22, 2008
Publication Date: June 1, 2008
Citation: Loving, C.L., Nicholson, T.L., Brockmeier, S. 2008. Bordetella bronchiseptica Bvg Phase-Dependent Contribution to Colonization, Transmission, and Immune Responses in Pigs [abstract]. American Society for Microbiology Meeting, June 2-4, 2008, Boston, Massachusetts. 2008 CDROM.

Technical Abstract: Bordetella bronchiseptica causes respiratory disease in several animal species, including swine. In pigs, B. bronchiseptica infection can result in bronchopneumonia, as well as make animals susceptible to secondary pathogens, resulting in severe respiratory disease. The mechanisms by which B. bronchiseptica can colonize and persist in pigs is unknown, though it is hypothesized that both pathogen and host responses are involved. Expression of virulence factors in Bordetella is regulated by the Bvg locus, which encodes the BvgA/BvgS two-component regulatory system. To investigate B. bronchiseptica Bvg phase-dependent contribution to colonization, contact transmission, and immune responses in swine, a series of isogenic mutants (bvg-, bvgi, and bvg+) in a swine B. bronchiseptica isolate (KM22) were made. We hypothesized that some level of BvgA activation would be required for disease. Results from an in vivo swine study indicate that activation of the Bvg system is required for colonization, as the bvg- strain did not colonize. In addition, full activation of the Bvg system is required for early, optimal nasal colonization, as pigs challenged with the bvgi strain had significantly less bacteria in the nasal cavity compared to bvg+ and wildtype infected pigs the first week after challenge. No significant differences in colonization by the bvgi, bvg+, and wildtype parent (KM22) were detected in the lower respiratory tract (trachea and lung) and these three strains transmitted to non-challenged pigs placed in direct contact with infected pigs. Lastly, IFN-y production by lymph node cells collected from challenged pigs was significantly lower in bvgi group compared to KM22 group. Overall, these results indicate that factors produced in the bvgi phase are sufficient for colonization and transmission in swine, as well as effecting host immune responses.