Effect of in vitro and in vivo 25-hydroxyvitamin D treatment on macrophages, T cells, and layer chickens during a coccidia challenge

This article describes the in vitro and in vivo effects of a 25-hydroxycholecalciferol (25[OH]D) treatment in layer hens during a mixed coccidia challenge. HD11 cells (chicken macrophage cell line) were treated in vitro with a coccidia antigen or in a medium supplemented with either 1,25-dihydroxycholecalciferol (1,25[OH]2D) or 25(OH)D. HD11 cells treated in vitro with 200 nM of 1,25(OH)2D had increased nitrite production (P < 0.01) compared with HD11 cells treated with 0 or 200 nM of 25(OH)D. Treating HD11 cells with 25(OH)D decreased IL-10 mRNA by 1.7-fold, but 1,25(OH)2D treatment increased the amount of IL-10 mRNA by 2.7-fold (P < 0.01) compared with the group treated with 0 nM of 25(OH)D. Post-coccidial antigen stimulation, 25(OH)D or 1,25(OH)2D treatment decreased (P < 0.01) 1α-hydroxylase mRNA amounts in HD11 cells. Stimulating primary T cells in vitro with Concanavalin A (Con-A) decreased (P = 0.020) the 1α-hydroxylase mRNA amounts by 3-fold. ConA-B1-VICK cells (chicken T cell line) stimulated with 100 nM 1,25(OH)2D or with supernatants from HD11 cells treated with 25(OH)D plus lipopolysaccharide (LPS) had 1.3-fold less (P < 0.01) interferon (IFN)-γ mRNA compared with the group treated with 25(OH)D. Layer birds were fed a basal diet supplemented with 25(OH)D at 6.25, 25, 50, or 100 μg/kg, and at 21 d of age orally challenged with 1 × 10(5) live coccidia oocysts. Compared with birds fed similar levels of 25(OH)D and unchallenged with the coccidia oocyst, birds challenged with the coccidia oocyst had 15% reduced BW gain in the groups supplemented with either 6.25, 25, or 50 μg/kg of 25(OH)D, but only a 4% reduced BW gain in birds fed 100 μg/kg of 25(OH)D (P < 0.01). Birds fed 100 μg/kg 25(OH)D had decreased (P = 0.012) CD8+ cell percentages in cecal tonsils in both coccidial oocyst challenged and unchallenged birds, compared with birds fed 6.25 μg/kg 25(OH) and unchallenged with coccidial oocysts. At 15 d post-coccidia challenge, birds fed 100 μg/kg 25(OH)D and challenged with coccidial oocysts had 17% more CD4+CD25+ cells (P = 0.018) in the cecal tonsil compared with the birds fed 100 μg/kg 25(OH)D and unchallenged with coccidial oocysts. At d 6 post-coccidia challenge, birds fed 100 μg/kg 25(OH)D had a 3.5-fold increase (P < 0.01) in IL-10 mRNA amounts in the cecal tonsils compared with birds fed 6.25 μg/kg 25(OH)D. In conclusion, supplementing birds with 100 μg/kg 25(OH)D could be a nutritional strategy to reduce the production losses post-coccidi