Polymorphic locus T1237C of the Toll-like receptor 9 gene in patients with pneumonia with influenza A/H1N1

Abstract

Aims of the study. To determine the frequency of occurrence of the TLR9 (T1237C) gene polymorphism and establish its contribution to the development of organ failure in patients with severe pneumonia due to influenza A/H1N1.

Materials and methods. 100 patients with pneumonia were examined. Of these, 45 patients with severe pneumonia, 55 with non-severe pneumonia. The age of the patients was 53 [37; 65] year. Men made up 48% and women 52%. Patients with severe pneumonia were divided into 2 groups: group 1 – with a SOFA score <2 points, group 2 – SOFA ≥2 points. Determination of SNP genes was carried out by PCR using standard kits from NPF Litech (Moscow). Amplification of TLR3 gene fragments was carried out in a thermal cycler (model “Bis”-M111, LLC “Bis-N”, Novosibirsk). Genomic DNA isolated from whole blood leukocytes using the “DNA Express Blood” reagent was analyzed, then an amplification reaction was carried out. Detection of the amplification product was carried out in a 3% agarose gel. Comparison of genotype frequencies in groups was carried out using the χ2 test with Yates' correction for continuity using a contingency table; if the expected events in one of the cells were less than 5, Fisher's exact test was used. To assess the association of genotypes with disease severity, odds ratios (OR; Odds Ratio) were calculated with 95% confidence intervals (CI) for genetic models (codominant, dominant, recessive, overdominant).

Results. It has been established that carriage of the –1237C allele is more often recorded in patients with severe pneumonia. When analyzing the frequency distribution of TLR9 gene genotypes (T1237C), an association with pneumonia was revealed, according to codominant (OR (95% CI) 0.422 (0.219 – 0.815) (p=0.026)), dominant (OR (95% CI) 0.436 (0.237 – 0.802) (p=0.011)) and overdominant (OR (95% CI) 0.450 (0.236 – 0.861) (p=0.023)) genetic models.

Conclusion. The data obtained allow us to consider TLR9 as a potential point of pharmacological inhibition, since pro-inflammatory factors are expressed through TLR pathways, including TLR9, which are potential “culprits” of the so-called cytokine storm and thrombotic complications underlying multiple organ failure in severe pneumonia.