Relative expression analysis of IL‐5 and IL‐6 genes in tropical sheep breed Pelibuey infected with Haemonchus contortus

Haemonchus contortus is a parasitic nematode of Pelibuey sheep, a meat breed used in tropical regions. Due to anthelmintic problems, the identification of hosts resistant to H. contortus is another option of control. The aim of this study was to analyse the relative expression of IL‐5 and IL‐6 genes in Pelibuey sheep after H. contortus infection. Nineteen lambs infected with H. contortus and three more lambs without infection were studied. The haemonchosis was determined by the number of eggs per gram of faeces (epg) and by the estimation of the percentage of the packed cell volume (%pcv). Peripheral blood mononuclear cells (PBMCs) were obtained to extract RNA at 0, 1, 2, 7, 14, 21 and 28 days after infection to quantify the relative expression of IL‐5, IL‐6 and GAPDH by real‐time PCR. Five lambs were classified as low responders (lr) to haemonchosis with averages of 1519 ± 315·3 epg and 31·49 ± 5·13%pcv, and 14 lambs were identified as high responders (hr) with averages of 530 ± 132 epg and 34·88 ± 3·75%pcv. The expression ratio of IL‐5 was significantly different compared with control lambs at 2, 7 and 14 days post‐infection (PI), and IL‐6 was significantly different after 14 days. The highest level of relative expression for IL‐5 and IL‐6 genes was 9·9‐fold and 12‐fold after 2 and 14 days for hr hosts (P < 0·05) compared with control group, respectively. In conclusion, the Pelibuey breed in grazing areas exhibited different expression of IL‐5 and IL‐6 obtained from PBMCs against H. contortus, suggesting the importance of these cytokines in regulating the nematode infection.