Single-nucleotide polymorphisms in the Toll-like receptor pathway increase susceptibility to infections in severely injured trauma patients

Abstract

Background: Sepsis and subsequent multiple-organ failure are the predominant causes of late mortality in trauma patients. Susceptibility and response to infection is, in part, heritable. Single-nucleotide polymorphisms (SNPs) in Toll-like receptor (TLR) and cluster of differentiation 14 (CD14) genes of innate immunity may play a key role. The aim of this study was to assess if SNPs in TLR/CD14 predisposed trauma patients to infection.

Methods: A prospective cohort of trauma patients (age 18-80 years; injury severity score [ISS] ≥ 16) admitted to a Level I trauma center between January 2008 and April 2011 was genotyped for SNPs in TLR2 (T-16934A and R753Q), TLR4 (D299G and T399I), TLR9 (T-1486C and T-1237C), and CD14 (C-159T) using high-resolution melting analysis. Association of genotype with prevalence of positive culture findings (gram positive, gram negative, fungi), systemic inflammatory response syndrome (SIRS), sepsis, septic shock, and mortality was tested with χ(2) and logistic regression analysis.

Results: Genotyping was performed for 219 patients, of whom 51% developed positive culture findings in sputum, wounds, blood, or urine. SIRS developed in 64%, sepsis in 36%, and septic shock in 17%. The TLR2 T-16934A TA genotype increased the risk of a gram-positive infection (odds ratio, 2.816; 95% confidence interval, 1.249-6.348; p = 0.013) and SIRS (odds ratio, 2.386; 95% confidence interval, 1.011-5.632; p = 0.047). Trends were noted for TLR9 and CD14 SNPs but did not reach statistical significance. Sepsis and septic shock were unrelated to any of the SNPs studied.

Conclusion: Aberrant functioning of the TLR/CD14 pathway of innate immunity changes the risk of infectious complications in severely injured trauma patients. Of the seven SNPs studied, the TLR2 T-16934A increased the risk, the TLR9 T-1486C SNPs may decrease the risk, and TLR4 variation seemed unrelated to outcome. Early genotyping may prove to be helpful in the future in identifying polytraumatized patients at risk for infectious outcome.

Level of evidence: Prognostic and epidemiologic study, level II.