Comparison of Th-2 Cytokines and Associated Gene Expression in Peripheral Blood of Resistant and Susceptible Garole Sheep Infected With Haemonchus contortus.

Abstract

Level of Th-2 cytokines (IL-4, IL-5, and IL-13) in serum and relative expression of associated cytokine genes (IL-4, IL-5, and IL-13) in peripheral blood along with other parameters of host resistance were compared between the resistant and susceptible Garole sheep infected with Haemonchus contortus. Resistant (n = 12) and susceptible Garole sheep (n = 12) were selected based on faecal egg count (FEC) and packed cell volume (PCV) and were divided into three equal groups: healthy control, infected resistant, and infected susceptible. Sheep of infected groups were orally challenged with infective larvae of H. contortus and then FEC, body weight, haemoglobin (Hb), PCV, peripheral eosinophil counts (PEC), and serum Th-2 cytokines concentration and associated gene (IL-4, IL-5, and IL-13) expressions were measured. Partial sequences of all the three cytokine genes were also analysed. Significantly (p < 0.05) lower FEC was observed in resistant sheep with no eggs in faeces from 31 to 35 DPI while the susceptible sheep continued to pass Haemonchus eggs through faeces till end of the study. Body weight, Hb, PCV, and PEC of resistant sheep were higher (p < 0.05) compared with susceptible sheep. Concentrations of Th-2 cytokines (IL-4, IL-5, and IL-13) as well as expression all the genes (IL-4, IL-5, and IL-13) were found to be greater (p < 0.05) in resistant sheep on different days post infection. No single nucleotide variation was observed in either of the three genes that could be suggested to be responsible host resistance. In resistant sheep, increased eosinophilia, Th-2 cytokine concentration, and relative expression Th-2 cytokine genes in peripheral blood were observed synchronously with that of the elimination of parasites indicating the role of those components in resistance against H. contortus and this needs to be explored by examining local reaction in the abomasum of infected host.