Gene Polymorphisms In Toll-like Receptor Signaling Pathway And Their Relationship With The Susceptibility And Prognosis Of Sever Sepsis

[Background] Sepsis is the leading cause of death in non-coronary ICUs and one of the most common causes of in-hospital death. Despite decades of research and the establishment of clinical guideline, the morbidity and mortality of severe sepsis and septic shock remain very high. About 20～30 percent sepsis patients may progress to severe sepsis, septic shock and multiple organ dysfunction syndrome (MODS) . More and more clinical studies have found that not all sepsis patients present with most similar clinical manifestations have similar prognosis or response to similar treatments. Most of the septic patients may recover with proper treatment. However, others may progress to severe sepsis, refractory hypotension or multiple organ system failure with very high mortality, despite the more intensive treatment. Can we find an effective tool or biomarker to identify patients who will develop severe sepsis and septic shock in the early stage, so as to make more intensive intervention earlier? Recent evidence suggests that the individual genetic makeup plays an important role in the susceptibility, severity and outcome. Sequencing of the human genome has demonstrated that many genes are polymorphic. The most frequent type of polymorphism is the single-nucleotide polymorphisms (SNPs). Many studies have suggested that SNPs are very useful for disease risk assessment, early diagnosis, prevention and treatment. In recent years, Toll-like receptor signaling pathway has been confirmed playing an essential role in the pathogenesis of sepsis. However little has been known about whether the toll-like receptor signaling pathway genes' SNPs are associated with the susceptibility and prognosis of severe sepsis.[Objective] To investigate the association between TLR2, TLR4, MyD88, IRAK1 and TOLLEP genes' polymorphisms and the susceptibility or the prognosis of severe sepsis.[Methods] 1. Totally, 360 sepsis patients were enrolled in this study. Hapmap database of Han Chinese population was used to select the Tag SNPs of the selected candidate gene. Primer3 software was used to design the sequencing primers for PCR. DNA was extracted from peripheral blood mononuclear cells using the QIAGEN DNA Kit. Genotyping was performed by sequencing the PCR products. 2. According to severity, 360 cases were divided into the mild groupand the sever sepsis group each with180 cases to investigate the association between TLR2, TLR4, MyD88, IRAK1 as well as TOLLIP genes'polymorphisms and the susceptibility of severe sepsis. 3. According to surviving, 360 cases were also divided into the surviving group and death group with 300 and 60 cases respectively to investigate the association between TLR2, TLR4, MyD88, IRAK1 as well as TOLLIP genes' polymorphisms and the prognosis of sepsis. 4. Genotype and allele distributions were compared by a two-tailedχ~2 test. Odds ratios(OR) and 95% confidence intervals (CI) were calculated to assess the relative disease risk conferred by allele.[Results] 1. Our study suggested that two SNPs (rs3793964 and rs5743947) in the introns of the Tollip gene were strongly associated with severe sepsis susceptibility. In severe sepsis group, the G allele frequency of rs3793964 was higher than that of mild sepsis group (odds ratio (OR) = 1.710). There was significant difference in allele frequency, genotype frequency and dominant genetic model between two groups( P < 0.05 ). The A allele frequency of rs5743947 in two groups was significant different ( P= 0.001; OR = 1.957). The genotype frequency and dominant genetic model were also significantly different between two groups(P < 0.05). All the SNPs of TLR2, TLR4, MyD88 and IRAK1 gene were not associated with the severe sepsis susceptibility. There was also no significant difference concerning the frequencies of haplotype of TLR4 and TOLLIP between the mild and severe sepsis group. 2. One SNP( rsl059702) was observed to be associated with the prognosis of sepsis. The C allele was more frequent in non-surviving group as compared to the surviving patients (P=0.0007; OR=2.014). Also there was significant difference of genotype between surviving and non-surviving group. However there were no associations between polymorphisms of TLR2, TLR4, MyD88, TOLLIP gene and the prognosis of severe sepsis. No associations were found between haplotypes of TLR4 and TOLLIP and the prognosis of severe sepsis.[Conclusions] Our study suggests that two SNPs of TOLLIP gene are significantly associated with the susceptibility to severe sepsis. Those patients who carry the G allele of SNP rs3793964 and the A allele of SNP rs5743947 in TOLLIP gene are more likely to develop severe sepsis. And one SNP of IRAK1 gene is associated with the prognosis of severe sepsis. Carriage of the C allele of SNP rs1059702 in IRAK1 gene is associated with poor outcome of severe sepsis patients.