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ARS Home » Midwest Area » Ames, Iowa » National Animal Disease Center » Virus and Prion Research » Research » Publications at this Location » Publication #355531

Research Project: Non-Antibiotic Strategies to Control Priority Bacterial Infections in Swine

Location: Virus and Prion Research

Title: Generation and evaluation of a Haemophilus parasuis capsule mutant

item Brockmeier, Susan
item Hau, Samantha - Orise Fellow
item Eberle, Kirsten - Orise Fellow
item Wang, Jinhong - University Of Cambridge
item Peters, Sarah - University Of Cambridge
item Tucker, Alexander - University Of Cambridge
item Maskell, Duncan - University Of Cambridge

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 8/23/2018
Publication Date: 10/8/2018
Citation: Brockmeier, S., Hau, S., Eberle, K.C., Wang, J., Peters, S.E., Tucker, A.W., Maskell, D.J. 2018. Generation and evaluation of a Haemophilus parasuis capsule mutant. MedVet Pathogens 2018 5th Prato Conference on Animnal Bacterial Pathogens, October 8-11, 2018, Prato, Italy. Abstract No. 29.

Interpretive Summary:

Technical Abstract: Haemophilus parasuis is a commensal of the upper respiratory tract in pigs and also the causative agent of Glasser's disease, which results in significant morbidity and mortality in pigs worldwide. Isolates of H. parasuis are characterized into 15 serotypes by their capsular polysaccharide. To investigate the role capsule plays in H. parasuis virulence and host interaction, a capsule mutant of the serotype 5 strain 265 was generated (265deltacap). The 265deltacap mutant was unable to cause signs of systemic disease during a pig challenge study and had increased sensitivity to complement killing. When compared to the parent strain, 265deltacap produced more robust biofilm and adhered equivalently to 3D4/31 cells; however, it was unable to persistently colonize the nasal cavity of inoculated pigs, with all pigs clearing 265deltacap by 5 days post-challenge. Only a mild increase in serum antibody to 265deltacap sonicate was seen post-exposure and upon intranasal challenge of the 265deltacap inoculated animals 21 days later with wild type H. parasuis 265, all animals developed clinical signs consistent with Glasser's disease and H. parasuis was isolated from one or more systemic sites (serosa, joint, serum, and/or cerebral spinal fluid) from all pigs. Our results indicate the importance of capsule to a fully virulent phenotype in vivo. Capsular polysaccharide plays an important role in resistance to complement killing, which may be a key factor in the dissemination of H. parasuis to systemic sites. In this study, we also found capsule to be an essential factor in H. parasuis 265 for persistent colonization of the swine nasal cavity. However, because of the rapid clearance of 265deltacap from the nasal cavity, generation of antibody was minimal and no protection was provided against challenge with the parent strain making 265deltacap a poor modified live vaccine candidate.