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United States Department of Agriculture

Agricultural Research Service

Research Project: IDENTIFICATION OF DISEASE MECHANISMS AND CONTROL STRATEGIES FOR BACTERIAL RESPIRATORY PATHOGENS IN CATTLE Title: Bivalent vaccination against pneumonic pasteurellosis in domestic sheep and goats with modified-live in-frame lktA deletion mutants of Mannheimia haemolytica

Authors
item BRIGGS, ROBERT
item Hauglund, Melissa
item Maheswarn, Samuel -
item TATUM, FRED

Submitted to: Microbial Pathogenesis
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 30, 2013
Publication Date: November 1, 2013
Citation: Briggs, R.E., Hauglund, M.J., Maheswarn, S., Tatum, F.M. 2013. Bivalent vaccination against pneumonic pasteurellosis in domestic sheep and goats with modified-live in-frame lktA deletion mutants of Mannheimia haemolytica. Microbial Pathogenesis. 64:43-47. DOI 10.1016/j.micpath.2013.08.004.

Interpretive Summary: Mannheimia haemolytica is a bacterium associated with pneumonia in domestic cattle, sheep, goats and wild bighorn sheep. Multiple serotypes of this bacterium are involved in disease of all affected species. Modified-live M. haemolytica vaccine strains were constructed and two were evaluated in a combination vaccine delivered to sheep and goats. Vaccinated animals were highly resistant to challenge by a combination of virulent strains. The results support the possibility that disease caused by all or most serotypes of M. haemolytica may be preventable using a single dose of modified-live combination vaccine.

Technical Abstract: A temperature-sensitive shuttle vector, pBB80C, was utilized to generate in-frame deletion mutants of the leukotoxin structural gene (lktA) of Mannheimia haemolytica serotypes 1, 2, 5, 6, 7, 8, 9, and 12. Culture supernatants from the mutants contained a truncated protein with an approximate molecular weight of 66 kDa which was reactive to anti-leukotoxin monoclonal antibody. No protein reactive to anti-LktA monoclonal antibody was detected at the molecular weight 100-105 kDa of native LktA. Sheep and goats vaccinated intramuscularly with a mixture of serotypes 5 and 6 mutants were resistant to virulent challenge with a mixture of the wild-type parent strains. These vaccinates responded serologically to both vaccine serotypes and exhibited markedly-reduced lung lesion volume and pulmonary infectious load compared to control animals. Control animals yielded a mixture of serotypes from lung lobes, but the proportion even within an individual animal varied widely from 95% serotype 5 to 95% serotype 6. Cultures recovered from liver were homogeneous, but two animals yielded serotype 5 and the other two yielded serotype 6 in pure culture.

Last Modified: 7/28/2014
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