Toll Like Receptor 9 (TLR9) Polymorphism G520R in Sheep Is Associated with Seropositivity for Small Ruminant Lentivirus

Infectious diseases of sheep are of major economic importance causing direct and indirect losses. Among the major sheep infectious agents are Small Ruminant Lentivirus, Chlamydophila abortus and Mycobacterium avium subsp. paratuberculosis infections, mainly due to their worldwide distribution and economic impact that they cause. Based on the differential susceptibility to infectious diseases between and within breeds and on the recent findings regarding the putative involvement of TLR9 in disease susceptibility, the aim of this study was to evaluate the levels of nucleotide variation of TLR9 and its mediator MyD88 in three sheep flocks originated from different breeds and assess their possible association with seropositivity/seronegativity for different infectious agents. The analysis indicated that the change of G to R at codon 520 of TLR9 polypeptide shows a significant association with Small Ruminant Lentivirus seropositivity. This amino-acid substitution, which can result in polarity change, might influence structure and function of LRR17, interfering with ligand binding and thus could be used in studies investigating susceptibility/resistance to Small Ruminant Lentivirus infections in sheep.