Comparative investigation of IFN-γ-producing T cells in chickens and turkeys following vaccination and infection with the extracellular parasite Histomonas meleagridis

The re-emerging disease histomonosis is caused by the protozoan parasite Histomonas meleagridis that affects chickens and turkeys. Previously, protection by vaccination with in vitro attenuated H. meleagridis has been demonstrated and an involvement of T cells, potentially by IFN-gamma production, was hypothesized. However, comparative studies between chickens and turkeys on H. meleagridis-specific T cells were not conducted yet. This work investigated IFN-gamma production within CD4(+), CD8 alpha(+) and TCR gamma delta(+) (chicken) or CD3 epsilon(+)CD4(-)CD8 alpha(+) (turkey) T cells of spleen and liver from vaccinated and/or infected birds using clonal cultures of a monoxenic H. meleagridis strain. In infected chickens, re-stimulated splenocytes showed a significant increase of IFN-gamma(+)CD4(+) T cells. Contrariwise, significant increments of IFN-gamma-producing cells within all major T-cell subsets of the spleen and liver were found for vaccinated/infected turkeys. This indicates that the vaccine in turkeys causes more intense systemic immune responses whereas in chickens protection might be mainly driven by local immunity.

• Phenotype and cytokine production of Histomonas meleagridis-specific T cells isolated from chickens and turkeys infected with the parasite or vaccinated against histomonosis.

Veterinärmedizinische Universität Wien