Contemporary evolution of the viral-sensing TLR3 gene in an isolated vertebrate population

Understanding where and how genetic variation is maintained within populations is important from an evolutionary and conservation perspective. Signatures of past selection suggest that pathogen-mediated balancing selection is a key driver of immunogenetic variation, but studies tracking contemporary evolution are needed to help resolve the evolutionary forces and mechanism at play. Previous work in a bottlenecked population of Seychelles warblers (Acrocephalus sechellensis) show that functional variation has been maintained at the viral-sensing Toll-like receptor 3 (TLR3) gene. Here, we characterise evolution at this TLR3 locus over a 25-year period within the original remnant population of the Seychelles warbler, and in four other derived, contained populations. Results show a significant and consistent temporal decline in the frequency of the TLR3C allele in the original population, and that similar declines in the TLR3C allele frequency occurred in all the derived populations. Individuals (of both sexes) with the TLR3CC genotype had lower survival, and males - but not females - that carry the TLR3C allele had significantly lower lifetime reproductive success than those with only the TLR3A allele. These results indicate that positive selection, caused by an as yet unknown agent, is driving TLR3 evolution in the Seychelles warblers. No evidence of heterozygote advantage was detected. However, whether the positive selection observed is part of a longer-term pattern of balancing selection (through fluctuating selection or rare-allele advantage) cannot be resolved without tracking the TLR3C allele in the populations over an extended period of time.

Influence of Age and Immunostimulation on the Level of Toll-Like Receptor Gene (TLR3, 4, and 7) Expression in Foals

The aim of this study was to investigate the molecular mechanisms leading to the identification of pathogens by congenital immune receptors in foals up to 60 days of age. The study was conducted on 16 foal Polish Pony Horses (Polish Konik) divided into two study groups: control (n = 9) and experimental (n = 7). Foals from the experimental group received an intramuscular duplicate injection of 5 mL of Biotropina (Biowet) at 35 and 40 days of age. The RNA isolated from venous blood was used to evaluate the expression of theTLR3, TLR4, and TLR7 genes using RT-PCR. The results of the experiment demonstrated a statistically significant increase in the level of TLR3 gene expression and a decrease in the level ofTLR4 gene expression with foal aging. The level of TLR7 gene expression did not show age dependence. Immunostimulation with Biotropina had a significant impact on the level of the genes’ expression for Toll-like receptors. It increased the level of TLR4 expression and decreased TLR3 expression. Thus, it was concluded that the expression of theTLR3 and TLR4genes in peripheral blood cells is dependent on age. This experiment demonstrated a strong negative correlation between TLR3 and TLR4 gene expression.

Study of Toll-like Receptor 3 Gene Polymorphism as a Novel Risk Factor for HCV-related Hepatocellular Carcinoma in Egypt

Background & Aims: Hepatocellular carcinoma (HCC) is a highly aggressive cancer with few treatment options. Toll-like receptor 3 (TLR3) plays a key role in innate immunity and may affect the development of cancers. This study aimed to investigate the association between TLR3 gene polymorphism and HCV-related hepatocellular carcinoma in Egypt. Methods: This work was conducted on 70 individuals; fifty HCV cirrhotic patients were included in two groups; with HCC (30 patients) and without HCC (20 patients) compared with a group of 20 apparently healthy controls. All of the studied individuals underwent clinical-laboratory evaluation. TLR3 gene single-nucleotide polymorphism (SNP) (+1234C/T) was tested by polymerase chain reaction- restriction fragment length polymorphism. Results: This study reported that the prevalence of TLR3 +1234TT genotype was significantly increased in cirrhotic patients with HCC than without HCC, while it was not detected at all among the controls. When analyzing the TLR3 SNP +1234C/T with different clinical parameters in HCC patients, there was a significant association between+1234C/T SNP; namely TT genotype and each of the hepatic focal lesions᾽ number, size and the patients᾽ higher Okuda and BCLC stages. No association could be detected between TLR3 SNP and the age, sex, Child-Pugh grades, MELD score or AFP of the studied HCC cases. Conclusion: TLR3 gene SN P +1234C/T could be a novel risk factor for the HCV-related HCC among the Egyptian population.

GENETIC POLYMORPHISM IN PATIENTS WITH EARLY AND LATE ONSET OF ULCERATIVE COLITIS

The aim was to investigate SNPs of TLR-2,3,4, NOD2/CARD15, JAK-2, and IL-10 in patients with the early and late UC onset. Matherials and methods: 126 patients with UC were investigated. To assess the predisposition of the early and late UC onset the incidence of the following SNPs: Arg753Gln TLR2 gene, Phe412Leu TLR3 gene, Asp299Gly and Thr399Ile TLR4 gene, C-819T, G-1082A and C-592A gene IL-10, Val617Phe gene JAK2, Gly908Arg gene NOD2/CARD15 were analyzed. Results: 76 patients had early disease onset and 50 had a late one. SNPs of TLR3 were observed in 50.8% cases. TLR4 polymorphism was more common than TLR3, and was observed in 81 (64.3%) UC patients. Polymorphism of NOD2/CARD15 and IL-10 genes were revealed with almost the same frequency 49 (38.9%) and 50 (39.9%) patients, respectively. Conclusions: Polymorphisms of TLR-2,3 genes and TLR4 Asp299Gly, NOD2/CARD15 prevailed in patients with the late UC onset that allows to suppose that bacterial flora plays one of the key roles in modification of immune response and UC development. In patients with early UC onset polymorphisms of the JAK2 and IL-10 genes prevailed responsible for the cytokine cascade activation and cause the immune mechanism that might lead to a more aggressive course of the disease.