Modulation of the spleen transcriptome in domestic turkey (Meleagris gallopavo) in response to aflatoxin B₁ and probiotics

Poultry are highly susceptible to the immunotoxic effects of the food-borne mycotoxin aflatoxin B₁ (AFB₁). Exposure impairs cell-mediated and humoral immunity, limits vaccine efficacy, and increases the incidence of costly secondary infections. We investigated the molecular mechanisms of AFB₁ immunotoxicity and the ability of a Lactobacillus-based probiotic to protect against aflatoxicosis in the domestic turkey (Meleagris gallopavo). The spleen transcriptome was examined by RNA sequencing (RNA-seq) of 12 individuals representing four treatment groups. Sequences (6.9 Gb) were de novo assembled to produce over 270,000 predicted transcripts and transcript fragments. Differential expression analysis identified 982 transcripts with statistical significance in at least one comparison between treatment groups. Transcripts with known immune functions comprised 27.6 % of significant expression changes in the AFB₁-exposed group. Short exposure to AFB₁ suppressed innate immune transcripts, especially from antimicrobial genes, but increased the expression of transcripts from E3 ubiquitin-protein ligase CBL-B and multiple interleukin-2 response genes. Up-regulation of transcripts from lymphotactin, granzyme A, and perforin 1 could indicate either increased cytotoxic potential or activation-induced cell death in the spleen during aflatoxicosis. Supplementation with probiotics was found to ameliorate AFB₁-induced expression changes for multiple transcripts from antimicrobial and IL-2-response genes. However, probiotics had an overall suppressive effect on immune-related transcripts.