Contagious bovine pleuropneumonia (CBPP) is a severe disease caused by Mycoplasma mycoides subsp. mycoides (Mmm). Knowledge on CBPP pathogenesis is fragmented and hampered by the limited availability of laboratory animal and in vitro models of investigation. The purpose of the present study is to assess respiratory explants as useful tools to study the early stages of CBPP. Explants were obtained from trachea, bronchi and lungs of slaughtered cattle, tested negative for Mycoplasma spp. and for the major bacterial and viral respiratory pathogens. The interaction of Mmm with explant cells was studied by immunohistochemistry (IHC), double-labelling indirect immunofluorescence (DLIIF) and laser scanning confocal microscopy (LSCM). Mmm capability to survive and proliferate within the explants was evaluated by standard microbiological procedures. Finally, the putative cellular internalization of Mmm was further investigated by the gentamicin invasion assay. IHC and DLIIF indicated that Mmm can colonize explants, showing a marked tropism for lower airways. Specifically, Mmm was detected on/inside the bronchiolar and alveolar epithelial cells, the alveolar macrophages and the endothelial cells. The interaction between Mmm and explant cells was abolished by the pre-incubation of the pathogen with bovine anti-Mmm immune sera. Mmm was able to survive and proliferate in all tracheal, bronchial and lung explants, during the entire time course of the experiments. LSCM and gentamicin invasion assay both confirmed that Mmm can enter non-phagocytic host cells. Taken together, our data supports bovine respiratory explants as a promising tool to investigate CBPP, alternative to cattle experimental infection.

Four goats were inoculated with an inactivated peste des petits ruminants virus (PPRV) vaccine. Three unvaccinated goats were kept as controls. After 36 days, the four goats were revaccinated. The immune response was monitored by virus neutralization test showing that two doses of the vaccine were able to stimulate strong immune response in all the vaccinated animals. The vaccinated goat and the controls were challenged with virulent PPRV intranasally. After PPRV challenge, the three control goats showed fever, viremia and virus excretion through mucosal surfaces, whereas the vaccinated goats were fully protected against PPRV infection and replication.

Contagious bovine pleuropneumonia (CBPP) is a significant respiratory disease in cattle caused by Mycoplasma mycoides subsp. mycoides (Mmm). A better understanding of the pathogenesis of CBPP and the immune response of the host to infection will assist in the development of novel interventions to prevent disease progression. In this study, bovine lung explants (BLEs) were exposed to Mmm to investigate the upregulation and release of early inflammatory cytokines, mediators and receptors following tissue infection. Immunomodulatory molecules indicative of cell activation were investigated by immunoblotting on the BLEs and the tissue culture supernatants, and quantitative real-time PCR (RTq-PCR) was performed on the BLEs to determine the fold change in the expression of the respective mRNA. Immunoblotting indicated the production of inflammatory cytokines, mediators and receptors in Mmm-infected BLEs; however, this contrasted strongly with the mRNA expression profile, which did not show any significant fold increase. Infection of the BLEs with Mmm stimulated the production of some pro-inflammatory cytokines and mediators, including IL-1β, COX-2, 5-LOX and iNOS. Toll-like receptor proteins TLR2 and TLR4 were detected solely in the tissue culture supernatant of Mmm-infected BLEs. These receptors are considered to be involved in the recognition of Mmm by BLE tissue cells, thus triggering intracellular pathways that produce specific inflammatory cytokines and mediators, initiating the inflammatory response.