Evaluation of the recombinant proteins RlpB and VacJ as a vaccine for protection against Glaesserella parasuis in pigs

Authors: HAU, SAMANTHA - Oak Ridge Institute For Science And Education (ORISE); LUAN, SHI-LU - University Of Cambridge; Loving, Crystal; Nicholson, Tracy; WANG, JINHONG - University Of Cambridge; PETERS, SARAH - University Of Cambridge; SEILLY, DAVID - University Of Cambridge; WEINERT, LUCY - University Of Cambridge; LANGFORD, PAUL - Imperial College; RYCROFT, ANDREW - University Of Cambridge; WREN, BRENDAN - London School Of Hygiene & Tropical Medicine; MASKELL, DUNCAN - University Of Cambridge; TUCKER, ALEXANDER - University Of Cambridge; Brockmeier, Susan

Submitted to: BMC Veterinary Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/14/2020
Publication Date: 5/28/2020
Publication URL: https://handle.nal.usda.gov/10113/6965730
Citation: Hau, S.J., Luan, S., Loving, C.L., Nicholson, T.L., Wang, J., Peters, S.E., Seilly, D., Weinert, L., Langford, P.R., Rycroft, A., Wren, B.W., Maskell, D.J., Tucker, A.W., Brockmeier, S. 2020. Evaluation of the recombinant proteins RlpB and VacJ as a vaccine for protection against Glaesserella parasuis in pigs. BMC Veterinary Research. 16:167. https://doi.org/10.1186/s12917-020-02377-5.
DOI: https://doi.org/10.1186/s12917-020-02377-5

Interpretive Summary: Glaesserella parasuis causes severe disease in pigs. It is difficult to prevent because vaccines do not prevent disease with all strains. There is now focus on developing vaccines from G. parasuis proteins. Protein vaccines could provide protection against many strains. We identified and evaluated the use of two G. parasuis proteins as vaccine candidates (RlpB and VacJ). The proteins induced high antibody levels, however, these antibodies were not able to protect pigs from challenge with G. parasuis. We think the reason the vaccine was not protective was because there isn’t enough RlpB and VacJ exposed on G. parasuis for the antibody to prevent disease.

Technical Abstract: Glaesserella parasuis, the causative agent of Glasser’s disease, is widespread in swine globally resulting in significant economic losses to the swine industry. Prevention of Glasser’s disease in pigs has been plagued with an inability to design broadly protective vaccines, as many bacterin based platforms generate serotype or strain specific immunity. Subunit vaccines are of interest to provide protective immunity to multiple strains of G. parasuis. Selected proteins for subunit vaccination should be widespread, highly conserved, and surface exposed. In this report, we report the identification of two candidate proteins for subunit vaccination (RlpB and VacJ) and evaluate recombinant RlpB and VacJ, outer membrane proteins with important contributions to cellular function and viability, as subunit vaccine candidates. Though high antibody titers to the recombinant proteins and increased interferon-gamma producing cells were found in subunit vaccinated animals, the pigs were not protected from developing systemic disease. It appears likely insufficient RlpB and VacJ are expressed on the bacterial surface for antibody to bind, preventing high RlpB and VacJ specific antibody titers from protecting animals from G. parasuis.