Omotainse, Oluwadamilola S.Wawegama, Nadeeka K.Kulappu Arachchige, Sathya N.Coppo, Mauricio CVaz, Paola K.Saliha, UneebBogeski, MirjanaNoormohammadi, Amir H.Stent, Andrew W.2025-01-152025-01-152023-12Veterinary Microbiology. Volume 287. December 2023. Article number 1099210378-1135https://repositorio.unab.cl/handle/ria/63031Indexación: ScopusMycoplasma synoviae is a pathogen of poultry that causes upper respiratory tract disease. MS-H is a live attenuated temperature-sensitive vaccine that effectively control M. synoviae infection in chickens. However, the mechanisms underpinning protection have not been described previously. In this study, specific-pathogen-free chickens were vaccinated at 3 weeks of age with MS-H vaccine and challenged with field strain M. synoviae 94011/v-18d at 6 weeks of age. Tracheal mucosal inflammation was characterised by the assessment of thickness, histopathological lesions, cellular infiltrates and cytokine transcription. Tracheal lesion scores of unvaccinated-challenged (-V+C) birds were higher than that of vaccinated-challenged (+V+C) birds. +V+C birds displayed early upregulation of IL-4, consistent with a Th-2-skewed response, followed by a later increase in IFN-γ transcription, indicating transition to a Th-1-skewed response. -V+C birds displayed a concurrent early Th-2 and Th-17 response characterised by increase expression of IL-4 and IL-17A respectively, and late T regulatory response characterised by increased IL-10 transcription. +V+C chickens had more cytotoxic T cells (CD8+ T cells) at 7- and 21 days post-challenge (dpc), while -V+C chickens had higher numbers of infiltrating CD4+CD25+ at 7 and 21 dpc. Overall, these observations suggest that the immune response in +V+C chickens had an inflammation characterised by an early Th-2 skewed response followed closely by a Th-1 response and infiltration of cytotoxic T cells, while the response in -V+C chickens was an early Th-2/Th-17-skewed response closely followed by a T regulatory response. © 2023 The AuthorsenCellular-responseCytokinesMS-H-vaccineMycoplasma SynoviaeTracheal-MucosaArtículo10.1016/j.vetmic.2023.109921