CategorySwine Health - General Disease
Date Full Report Received11/01/2018
Date Abstract Report Received11/01/2018
InvestigationInstitution: Regents of the University of Minnesota
Primary Investigator: Dr. Maria Pieters DVM
Funded ByNational Pork Board
Gilt acclimation for M. hyopneumoniae has been proposed as a strategy to control this respiratory bacterium in breeding herds. Despite the fact that vaccination is currently the most utilized strategy for gilt acclimation, intentional exposure to M. hyopneumoniae is increasing in popularity in some parts of the world. The objective of this study was to compare the effectiveness and consistency of four M. hyopneumoniae exposure methods based on M. hyopneumoniae detection, disease development, and humoral immune response against the bacterium. Forty M. hyopneumoniae negative gilts were distributed into five experimental groups according to the inoculation methods: 1) Intra-tracheal catheter (ITc; n=5); 2) Laryngo-Tracheal Mucosal Atomization device (LTMA; n=10); 3) Intranasal device (INd; n=10); 4) Rope chewing (RCh; n=10); 5) Mock-inoculated (MI; n=5). Laryngeal swabs and blood samples were collected at 0, 14, and 28 days post-inoculation (dpi) to detect M. hyopneumoniae by rt-PCR and to assess the presence of antibodies by ELISA. All gilts were euthanized at 28 dpi for lung lesion assessment and sample collection. Gilts in MI group remained negative throughout the study. A statistical difference in detection of M. hyopneumoniae was observed between ITc and LTMA compared to INd and RCh at 28 dpi. All gilts remained seronegative at 28 dpi, except two in ITc (2/5, 40%) and five in LTMA (5/10, 50%). The LTMA and ITc groups showed numerically higher cough indices than INd and RCh. Under the conditions of this study, LTMA route was equally effective in inducing M. hyopneumoniae infection as ITc (standard infection model). In conclusion, the LTMA for M. hyopneumoniae infection could represent a novel, safe and effective route, offering ease of application to inoculate gilts against this bacterium.
Results indicate that M. hyopneumoniae vaccination induced a rapid adaptive cellular immune response as early as two weeks post-vaccination, whereas humoral responses were only detected four weeks post-vaccination . Furthermore, they revealed an independent dynamic of specific T-cell and antibody responses to M. hyopneumoniae vaccination and infection. Nonetheless, no significant differences in cellular immune responses between different treatment groups, post-infection was observed suggesting that timing and non-specific PMBC stimulation might have impacted our results.
Although, M. hyopneumoniae induced cell-mediated immunity has been associated with protection from disease, limited evidence is available for cell-mediated immunity to M. hyopneumoniae after vaccination. Therefore, future experiments on antigen specific T cell and B cell responses will help better understand cellular immune function in hosts and will reveal alternative cellular assay based methods to measure vaccine efficacy.