Expression of Toll-like receptors in Haemonchus Contortus resistant sheep: An innate immune parameter for host defense against gastrointestinal nematode infection

Abstract

Innate immune parameters, a first line of defense against invading pathogens like bacteria, parasites, fungi, etc, play a significant role in the prevention and elimination of aetiological agents primarily by recognition of invading pathogen-specific molecules by different pattern recognition receptors. Toll-like receptors (TLRs), a type-I transmembrane glycoprotein, cause innate immune responses mainly by produing inflammatory cytokines, chemokines and interferons. The objective of present study was to determine the role of TLRs in parasite resistance in Malpura sheep. In the current study, transcript variation of TLRs and its downstream signalling molecules namely MyD88, TRIF, IRF-3, TRAF, TGF-β, NFκB, and CD14 were ascertained by real-time PCR in Haemonchus contortus resistant (R) and susceptible (S) Malpura sheep. Results have shown significantly (P<0.05) up-regulated expression of TLR-2, TLR-4, TLR-5, TLR-8 and TLR-10 in July however down-regulated patterns were observed in August and September in R-line sheep compared to S-line sheep. This indicates that at more or less equal parasite load, the TLR genes in R sheep produce more transcripts, but after parasite loads have increased hugely in the S line, they easily surpass the levels seen in the S line. Result suggests that transcriptional activity of the TLR genes was related to parasite load and there were differences between the lines at different infection intensities. Three-point transcript expression observation of the signalling molecules namely TRIF, IRF-3, TRAF, a similar pattern was observed in R sheep compared with S sheep.