Deoxynivalenol (DON) is one of the most prevalent mycotoxins, contaminating cereals and cereal-derived products. Its derivative deepoxy-deoxynivalenol (DOM-1) is produced by certain bacteria, which either occur naturally or are supplemented in feed additive. DON-induced impairments in protein synthesis are particularly problematic for highly proliferating immune cells. This study provides the first comparison of the effects of DON and DOM-1 on the concanavalin A-induced proliferation of porcine, chicken, and bovine peripheral blood mononuclear cells (PBMCs). Therefore, isolated PBMCs were treated with DON (0.01–3.37 µM) and DOM-1 (1.39–357 µM) separately, and proliferation was measured using a bromodeoxyuridine (BrdU) assay. Although pigs are considered highly sensitive to DON, the present study revealed a substantially higher sensitivity of bovine (IC50 = 0.314 µM) PBMCs compared to chicken (IC50 = 0.691 µM) and porcine (IC50 = 0.693 µM) PBMCs. Analyses on the proliferation of bovine T-cell subsets showed that all major subsets, namely, CD4⁺, CD8β⁺, and γδ T cells, were affected to a similar extent. In contrast, DOM-1 did not affect bovine PBMCs, but reduced the proliferation of chicken and porcine PBMCs at the highest tested concentration (357 µM). Results confirm the necessity of feed additives containing DON-to-DOM-1-transforming bacteria and highlights species-specific differences in the DON sensitivity of immune cells.

The Fusarium mycotoxin deoxynivalenol (DON) contaminates animal feed worldwide. In vivo, DON modifies the cellular protein synthesis, thereby also affecting the immune system. However, the functional consequences of this are still ill-defined. In this study, peripheral blood mononuclear cells from healthy pigs were incubated with different DON concentrations in the presence of Concanavalin A (ConA), a plant-derived polyclonal T-cell stimulant. T-cell subsets were investigated for proliferation and expression of CD8α, CD27, and CD28, which are involved in activation and costimulation of porcine T cells. A clear decrease in proliferation of all ConA-stimulated major T-cell subsets (CD4⁺, CD8⁺, and γδ T cells) was observed in DON concentrations higher than 0.4 µM. This applied in particular to naïve CD4⁺ and CD8⁺ T cells. From 0.8 μM onwards, DON induced a reduction of CD8α (CD4⁺) and CD27 expression (CD4⁺ and CD8⁺ T cells). CD28 expression was diminished in CD4⁺ and CD8⁺ T cells at a concentration of 1.6 µM DON. None of these effects were observed with the DON-derivative deepoxy-deoxynivalenol (DOM-1) at 16 µM. These results indicate that DON reduces T-cell proliferation and the expression of molecules involved in T-cell activation, providing a molecular basis for some of the described immunosuppressive effects of DON.

The protozoan parasiteHistomonas meleagridisis the causative agent of the re-emerging disease histomonosis of chickens and turkeys. Due to the parasite’s extracellular occurrence, a type-2 differentiation ofH. meleagridis-specific T cells has been hypothesized. In contrast, a recent study suggested that IFN-γ mRNA⁺cells are involved in protection against histomonosis. However, the phenotype and cytokine production profile ofH. meleagridis-specific T cells still awaits elucidation. In this work, clonal cultures of a virulent monoxenic strain ofH. meleagridiswere used for infecting chickens to detect IFN-γ protein and IL-13 mRNA by intracellular cytokine staining and PrimeFlow™ RNA Assays, respectively, in CD4⁺and CD8β⁺T cells. Infection was confirmed by characteristic pathological changes in the cecum corresponding withH. meleagridisdetection by immunohistochemistry andH. meleagridis-specific antibodies in serum. In splenocytes stimulated either withH. meleagridisantigen or PMA/ionomycin, IFN-γ-producing CD4⁺T cells from infected chickens increased in comparison to cells from non-infected birds 2 weeks and 5 weeks post-infection. Additionally, an increase of IFN-γ-producing CD4⁻CD8β⁻cells uponH. meleagridisantigen and PMA/ionomycin stimulation was detected. Contrariwise, frequencies of IL-13 mRNA-expressing cells were low even after PMA/ionomycin stimulation and mainly had a CD4⁻CD8β⁻phenotype. No clear increase of IL-13⁺cells related toH. meleagridisinfection could be found. In summary, these data suggest thatH. meleagridisinfection induces a type-1 differentiation of CD4⁺T cells but also of non-CD4⁺cells. This phenotype could include γδ T cells, which will be addressed in future studies.