T-2 toxin impairs antifungal activities of chicken macrophages against Aspergillus fumigatus conidia but promotes the pro-inflammatory responses

Abstract

Aspergillosis is the most common fungal disease of the avian respiratory tract and is caused primarily by Aspergillus fumigatus. The respiratory macrophages provide important defence against aspergillosis. T-2 toxin (T-2), a trichothecene mycotoxin produced by Fusarium spp. in improperly stored agricultural products, has immunomodulatory effects. We studied the impact of T-2 on the antifungal response of the chicken macrophage cell line HD-11 against A. fumigatus infection. The macrophages were first exposed to 0.5 to 10 ng/ml T-2 for 24 h, and then their viability, antifungal activity, and cytokine expression in response to A. fumigatus conidial infection were determined. The viability of macrophages decreased when exposed to T-2 at concentrations higher than 1 ng/ml. One hour after conidial infection, phagocytosed conidia were observed in 30% of the non-T-2-exposed macrophages, but in only 5% of the macrophages exposed to 5 ng/ml T-2. Seven hours after infection, 24% of the conidia associated with non-T-2-exposed macrophages germinated, in contrast to 75% of those with macrophages exposed to 5 ng/ml T-2. A. fumigatus infection induced upregulation of interleukin (IL)-1β, CXCLi1, CXCLi2 and IL-12β, and downregulation of transforming growth factor-β4 in macrophages. Exposure of A. fumigatus-infected macrophages to T-2 at 1 to 5 ng/ml further upregulated the expression of IL-1β, IL-6, CCLi2, CXCLi1, CXCLi2, IL-18 (at 1 and 2 ng/ml) and IL-12β, and further downregulated that of transforming growth factor-β4 (at 5 ng/ml). In conclusion, T-2 impaired the antifungal activities of chicken macrophages against A. fumigatus conidia, but might stimulate immune response by upregulating the expression of pro-inflammatory cytokines, chemokines and T-helper 1 cytokines.

Acknowledgements

The authors hereby express the most sincere and hearty gratitude to Dr Virginie Vandenbroucke, Mr Guangzhi Zhang, Ms Pascale Van Rooij, Ms Mojdeh Sharifian-Fard, Ms Miet Vermoote, Ms Myrthe Joosten, Dr Connie Adriaensen, Ms Venessa Eeckhaut, Mr Gunther Antonissen and Dr David Hermans for their technical advice and assistance.