Characterization of ovine Toll-like receptor 9 protein coding region, comparative analysis, detection of mutations and maedi visna infection

Single Nucleotide Polymorphisms in Genes Encoding Toll-Like Receptors 7 and 8 and Their Association with Proviral Load of SRLVs in Goats of Polish Carpathian Breed

Toll-like receptors (TLRs) 7 and 8 are important in single-stranded viral RNA recognition, so genetic variation of these genes may play a role in SRLVs infection and disease progression. Present study aimed to identify SNPs in genes encoding TLR7 and TLR8 in goats of Carpathian breed and analyze their association with the SRLVs provirus concentration as index of disease progression. A total of 14 SNPs were detected, 6 SNPs in the TLR7 gene locus and 8 SNPs in the TLR8 gene. Nine of the 14 identified polymorphisms, 4 in the TLR7 gene and 5 in TLR8 gene, were significantly associated with the SRLVs proviral concentration. These SNPs were located in 3'UTR, 5'UTR and intron sequences as well as in the coding sequences, but they led to silent changes. Homozygous genotypes of three TLR7 SNPs (synonymous variant 1:50703293, 3'UTR variant 1:50701297 and 5'UTR variant 1:50718645) were observed in goats with lower provirus copy number as well as in seronegative animals. The results obtained in this study suggest that SNPs of TLR7/TLR8 genes may induce differential innate immune response towards SRLVs affecting proviral concentration and thereby disease pathogenesis and progression. These findings support a role for genetic variations of TLR7 and TLR8 in SRLVs infection and warrants further studies on the effect of TLR7/TLR8 polymorphisms on SRLVs infection in different populations.

Sequence and functional variability of Toll-like receptor 9 gene in equines

Significant structural differences in the extracellular domain of toll-like receptor 9 (TLR9) account for species-specific recognition of its ligand CpG-ODN sequences. TLR9 is extensively studied in human, mice and some domestic animals. The recognition ability appears to be utilized differently by various species and breeds, but so far no comprehensive study exists about the equine TLR9 gene. We characterized TLR9 sequences of Marwari and Zanskari breeds of horses and Poitu donkey. We sequenced and identified the protein coding regions of equine TLR9 and compared with other animals and human beings. Furthermore, we also analyzed the amino acid substitutions and their likely implications on functions. The analysis revealed 14% evolutionary divergence between equine and human TLR9, while it was 1% between the Equus caballus and Equus asinus and less than 1% within Equus caballus. In phylogenetic analysis of predicted amino acids, the indigenous equines grouped with thoroughbred Equus caballus, while human, cattle, dog, sheep, mice, and buffalo formed separate clades. Furthermore, we also analyzed the amino acid substitutions and their likely implications on functions by sorting intolerant from tolerant (SIFT) analysis and predicted two substitutions of amino acids (D80N and S822P) in Marwari horses in leucine rich repeat 1 (LRR1) without any functional effects. The substitutions (V214A and Y579C) in LRR 3 and LRR11 in Zanskari horses were predicted to have functional consequences. Out of overall 8 substitutions, three substitutions (I420V, S970R and R1001C) were found in Equus asinus in LRR7, LRR 13, and toll interleukin receptor (TIR) domains, while the substitution G649S is observed in Poitu donkey only. We report for the first time that despite the conserved residues, the striking effect of substitutions, found within the TLR9 genes of different equine breeds/species may have possible implications.

Prospects in Innate Immune Responses as Potential Control Strategies against Non-Primate Lentiviruses

Lentiviruses are infectious agents of a number of animal species, including sheep, goats, horses, monkeys, cows, and cats, in addition to humans. As in the human case, the host immune response fails to control the establishment of chronic persistent infection that finally leads to a specific disease development. Despite intensive research on the development of lentivirus vaccines, it is still not clear which immune responses can protect against infection. Viral mutations resulting in escape from T-cell or antibody-mediated responses are the basis of the immune failure to control the infection. The innate immune response provides the first line of defense against viral infections in an antigen-independent manner. Antiviral innate responses are conducted by dendritic cells, macrophages, and natural killer cells, often targeted by lentiviruses, and intrinsic antiviral mechanisms exerted by all cells. Intrinsic responses depend on the recognition of the viral pathogen-associated molecular patterns (PAMPs) by pathogen recognition receptors (PRRs), and the signaling cascades leading to an antiviral state by inducing the expression of antiviral proteins, including restriction factors. This review describes the latest advances on innate immunity related to the infection by animal lentiviruses, centered on small ruminant lentiviruses (SRLV), equine infectious anemia virus (EIAV), and feline (FIV) and bovine immunodeficiency viruses (BIV), specifically focusing on the antiviral role of the major restriction factors described thus far.

Caprine Toll-like receptor 8 gene sequence characterization reveals close relationships among ruminant species

TLR8 mediates antiviral immunity by recognizing ssRNA viruses and triggers potent antiviral and antitumor immune responses. In this study, approximately 3.5 Kb nucleotide sequence data of caprine TLR8 gene were generated from one sample each of twelve different Indian goat breeds belonging to different geographical regions. Cloning and characterization of cDNA synthesized from RNA purified from goat spleen revealed TLR8 ORF to be of 3102 nucleotides long coding for 1033 amino acids similar to other ruminant species, that is sheep, buffalo and cattle. The sequence analysis at nucleotide level revealed goat TLR8 to be closer to buffalo sharing 99.6% homology, followed by cattle and sheep. Simple Modular Architecture Research Tool (SMART) used for the structural analysis of goat TLR8 showed the presence of 16 leucine-rich repeats (LRRs) along with single Toll/interleukin-1 receptor (TIR) domain. TIR domain when compared with other livestock species was found to be conserved in ruminant species goat, sheep, cattle and buffalo. The phylogenetic analysis also revealed grouping of all ruminant species together, goat being closer to buffalo followed by cattle and sheep. Total 4 polymorphic sites were observed in TLR8 gene of one specimen goat representing each of 12 different breeds studied, all of which were synonymous and present within the coding region. Of these 4 SNPs, two were in ectodomains, one in TIR domain and one was found to be present in transmembrane domain. PCR-RFLP genotyping of two of the SNPs indicated variations in allele frequencies among different goat breeds. The expression profiling in 13 tissues of goat showed maximum expression of TLR8 gene in kidney followed by spleen, lung and lymph node. Overall, our results indicate conservation of TLR8 gene among the ruminant species and low variation within Indian goat breeds.

Expanding possibilities for intervention against small ruminant lentiviruses through genetic marker-assisted selective breeding

Small ruminant lentiviruses include members that infect sheep (ovine lentivirus [OvLV]; also known as ovine progressive pneumonia virus/maedi-visna virus) and goats (caprine arthritis encephalitis virus [CAEV]). Breed differences in seroprevalence and proviral concentration of OvLV had suggested a strong genetic component in susceptibility to infection by OvLV in sheep. A genetic marker test for susceptibility to OvLV has been developed recently based on the TMEM154 gene with validation data from over 2,800 sheep representing nine cohorts. While no single genotype has been shown to have complete resistance to OvLV, consistent association in thousands of sheep from multiple breeds and management conditions highlight a new strategy for intervention by selective breeding. This genetic marker-assisted selection (MAS) has the potential to be a useful addition to existing viral control measures. Further, the discovery of multiple additional genomic regions associated with susceptibility to or control of OvLV suggests that additional genetic marker tests may be developed to extend the reach of MAS in the future. This review will cover the strengths and limitations of existing data from host genetics as an intervention and outline additional questions for future genetic research in sheep, goats, small ruminant lentiviruses, and their host-pathogen interactions.

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.

The immunopathology of sepsis: pathogen recognition, systemic inflammation, the compensatory anti-inflammatory response, and regulatory T cells

Sepsis, the systemic inflammatory response to infection, represents the major cause of death in critically ill veterinary patients. Whereas important advances in our understanding of the pathophysiology of this syndrome have been made, much remains to be elucidated. There is general agreement on the key interaction between pathogen-associated molecular patterns and cells of the innate immune system, and the amplification of the host response generated by pro-inflammatory cytokines. More recently, the concept of immunoparalysis in sepsis has also been advanced, together with an increasing recognition of the interplay between regulatory T cells and the innate immune response. However, the heterogeneous nature of this syndrome and the difficulty of modeling it in vitro or in vivo has both frustrated the advancement of new therapies and emphasized the continuing importance of patient-based clinical research in this area of human and veterinary medicine.