Efficacy of genetically modified Mycoplasma hyopneumoniae strains and their effect on local and cell-mediated immune responses in pigs

Abstract:Vaccination against Mycoplasma hyopneumoniae is still carried out worldwide, but unfortunately current commercial vaccines only provide partial protection. Therefore, two M. hyopneumoniae strains were genetically modified by transposon-mediated gene disruption of mmsA and mnuA, encoding methylmalonate semialdehyde dehydrogenase and membrane nuclease A, respectively. We investigated how immune responses elicited by these genetically modified M. hyopneumoniae strains protected pigs against challenge infection. An endotracheal single dose vaccination with genetically modified M. hyopneumoniae strain 1 (Delta mmsA) or 2 (Delta mnuA), or physiological saline solution (Control) was followed by challenge infection. Piglets from Delta mnuA had a higher respiratory disease score post-vaccination, but this group coughed significantly less after challenge. Significantly fewer DNA copies of the challenge strains were observed in broncho-alveolar lavage fluid (BAL) from Delta mnuA after challenge. Two weeks post-challenge, significantly more BAL IgG and BAL IgA was observed in Delta mnuA, but at euthanasia significantly more IgA and less pro-inflammatory cytokines were detected in BAL from both vaccinated groups. Furthermore, a significantly lower percentage of IFN-gamma+ and TNF-alpha+IFN-gamma+ CD8+ T cells was observed after administration of Delta mnuA. The percentage of IFN-gamma+ CD8+ T cells was significantly lower in Delta mmsA at euthanasia. To conclude, the results of this exploratory study show that a single endotracheal administration of Delta mnuA resulted in coughing post-vaccination, but reduced clinical signs post-challenge and challenge strain DNA load in BAL. Therefore, a strain mutated in the mnuA gene might be an interesting mutant strain that could be promising as a potential live vaccine candidate strain as it can reduce M. hyopneumoniae infection burden under field conditions.

Publication year:2025

Accessibility:Open