Comparative in vitro toll-like receptor ligand induced cytokine profiles of Toda and Murrah buffaloes-Identification of tumour necrosis factor alpha promoter polymorphism

Comparative analysis of innate immune response following in vitro stimulation of sheep and goat peripheral blood mononuclear cells with bluetongue virus - serotype 23

Bluetongue is an infectious disease caused by bluetongue virus (BTV), which affects sheep, goat, cattle and certain wild ruminants. However severe clinical signs are usually seen with significant mortality in sheep than cattle and goat. To date, comparative studies on innate immune responses of sheep and goat infected with BTV is lacking. In this study, we compared the innate immune response of sheep and goat by infecting the peripheral blood mononuclear cells (PBMCs) with BTV serotype 23. In our study, we observed that sheep PBMCs supports higher virus replication than goat PBMCs. To delineate the role of innate immune response in differential viral replication observed in this study, we examined TLR3 (Receptor for dsRNA virus) mRNA expression and cytokine profiles (IL-1β, Il-6, IL-8, Il-10, IL-12p40, TNF-α, IFN-γ and IFN-α) following Poly I:C (TLR3 ligand) stimulation and BTV 23 infection. In our present study, sheep PBMCs had significantly higher TLR3 mRNA levels, TLR3 specific ligand (Poly I:C) stimulation resulted in increased levels of IFN-γ at transcriptional and translational levels along with IL-8 and IL-10 at transcriptional levels. Whereas, the levels of TNF-α was higher in goat PBMCs at transcriptional levels. BTV infected sheep PBMCs expressed significantly higher levels of IFN-γ at transcriptional and translational levels along with IL-6, IL-8 and IL-10 at transcriptional levels. Whereas the expression levels of TNF-α and IFN-α at transcriptional and translational levels were significantly high in goat PBMCs. To examine the potential factor for consistent increase in the expression of TNF-α, we sequenced the promoter region of TNF-α and identified a total of five single nucleotide polymorphisms (SNP) and one indel in goat TNF-α promoter region. Luciferase assay for transcriptional activity of the promoter showed that goat TNF-α has significantly enhanced transcriptional activity in comparison with sheep TNF-α promoter. Altogether, our data suggests that the expression levels of TNF-α and IFN-α and/or IL-10 plays crucial role in replication of BTV 23.

Homology modeling and structural comparison of leucine rich repeats of Toll like receptors 1-10 of ruminants

Toll-like receptors (TLRs) are transmembrane receptors composed of extra cellular leucine rich repeats (LRRs) that identify specific pathogen associated molecular patterns triggering a innate immune cascade. The LRR regions of TLR 1-10 proteins of goat (Capra hircus), sheep (Ovis aries), buffalo (Bubalus bubalis) and bovine (Bos taurus) were modeled using MODELLER 9v7 tool and validated. The similarities and variations of these 10 TLRs extracellular regions of each species were compared using online servers like FATCAT, SSM and SSAP. It was evident that the LRRs of TLRs like 1, 2, 3 and 6 showed structural convergence with <1 % RMSD deviation while TLRs like 5, 7, 8 and 9 had high divergence. Docking analysis showed that TLR 2, 3 and 7 of all the selected four ruminant species were able to bind with their corresponding ligands like Peptidoglycan (PGN), Poly I:C, Resiquimod (R-848) and Imiquimod. However, there were variations in the active site regions, interacting residues and the number of bonded interactions. Variations seen among TLR structures and their ligand binding characteristics is likely to be responsible for species and breed specific genetic resistance observed among species or breeds.