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United States Department of Agriculture

Agricultural Research Service

Title: IgA Protease Activity in Haemophilus parasuis in the Absence of a Recognizable IgA Protease Gene

item Mullins, Michael
item Register, Karen
item Butler, John

Submitted to: American Society for Microbiology General Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 3/19/2010
Publication Date: 5/24/2010
Citation: Mullins, M., Register, K.B., Butler, J.E. 2010. IgA Protease Activity in Haemophilus parasuis in the Absence of a Recognizable IgA Protease Gene [abstract]. American Society for Microbiology. Poster No. Z-500.

Interpretive Summary:

Technical Abstract: Background. Haemophilus parasuis, the bacterium responsible for Glasser’s disease, is a pathogen of significant concern in modern high-health swine production systems. Little is known regarding the molecular mechanisms of H. parasuis infection. In some Pasteurellaceae species, IgA proteases aid in defeating the host immune response and facilitating disease. To better understand the mechanisms of Glässer’s disease in swine, we attempted to detect, compare, and analyze IgA protease activity in H. parasuis. Methods. H. parasuis culture supernatants were incubated for 18 hr at 37C with swine IgA**a or IgA**b (short-hinged) allotypic variants. Haemophilus influenzae culture supernatants incubated with human IgA served as positive controls. Following SDS-PAGE, IgA was detected with specific antiserum by Western blotting. Oligonucleotide primers and DNA probes specific for known IgA protease genes of H. influenzae, iga1 and igab, were used for PCR and Southern blotting in attempts to detect orthologous genes in H. parasuis. Results. Supernatants from 3 of 5 H. parasuis strains tested resulted in cleavage of both IgA**a and IgA**b, as evidenced by a reduction in the intensity of intact IgA (~60Kd) and appearance of a digestion product of ~45Kd common to both allotypes. The IgA**b digestion pattern additionally included a doublet of ~35Kd and a band of ~12 Kd. No cleavage of human IgA was observed for any H. parasuis strain. H. influenzae control supernatants cleaved human, but not swine, IgA. The iga1 and igab genes were detected in the appropriate H. influenzae strains by both PCR and Southern blotting, but no evidence for orthologous genes in any H. parasuis strain was obtained. Conclusions. Our results demonstrate, for the first time, that some strains of H. parasuis are able to cleave swine IgA. Further research will be needed to identify the genes involved and the role such activity may play in systemic spread of H. parasuis in swine.

Last Modified: 10/17/2017
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