γδ T cells induced by zoledronate under macrophage-depleted conditions reduce disease severity and parasite number in Eimeria tenella-infected chicks.

Abstract

Disease severity and local immune responses mediated by Zoledronate (ZOL)-induced &#x3b3;&#x3b4; T cells were evaluated in chicks infected with E. tenella under macrophage-depleted conditions. Three groups of White Leghorns, including a negative control group (CT), carrageenan-treated group (CAR), and both ZOL and CAR-treated group (ZOL/CAR), were infected orally with E. tenella sporulated oocysts (1&#xa0;&#xd7;&#xa0;10oocysts/chick) at 14&#xa0;days of age. Fecal oocyst shedding was assessed at 4-15&#xa0;days post-infection. The cecum was collected for histopathological and gene expression analyses. Oocyst shedding was significantly reduced in the CAR and ZOL/CAR groups compared with the CT group (p&#xa0;<&#xa0;0.01). The total oocyst number in the ZOL/CAR group was lower compared with those in the CAR and CT groups (p&#xa0;<&#xa0;0.05). The lesion score and parasite burden in the CAR and ZOL/CAR groups were lower compared with those in the CT group (p&#xa0;<&#xa0;0.01). The expression of IFN-&#x3bb;, IL-17&#xa0;A, and perforin mRNA in the ZOL/CAR group increased compared with that in the CAR group, whereas the expression of IFN-&#x3b3; in the ZOL/CAR group decreased. The results suggest that Th1-independent immunity occurs as a local immune response induced by IL-17&#xa0;A/IL-22-producing &#x3b3;&#x3b4; T cells, which control E. tenella-induced pathology in the cecum.