GENETIC POLYMORPHISMS IN TOLL-LIKE RECEPTOR 2, TOLL-LIKE RECEPTOR 4, NUCLEAR FACTOR-KAPPA B, AND INTERLEUKIN-4 GENES AND THEIR ASSOCIATION WITH CHRONIC PERIODONTITIS

Abstract

Objectives: Chronic periodontitis is a multifactorial inflammatory disease with a significant genetic component. Polymorphisms in genes involved in innate immunity and inflammatory regulation (toll-like receptor 2 [TLR2], toll-like receptor 4 [TLR4], nuclear factor-kappa B [NF-κB], and interleukin 4 [IL-4]) have been implicated in disease susceptibility and severity, though results remain inconsistent across populations. This study aimed to investigate the association of selected single-nucleotide polymorphisms in these genes with the risk and severity of chronic periodontitis in a South Indian population.

Methods: A case–control study was conducted at Government Medical College, Mahbubnagar, Telangana, India. The study included 100 patients with chronic periodontitis (cases) and 30 periodontally healthy controls (total n=130). Diagnosis followed the 2017 World Workshop classification. Genomic DNA was extracted from peripheral blood, and genotyping of four polymorphisms, TLR2 Arg753Gln (rs1898830), TLR4 Asp299Gly (rs7873784), NF-κB −94 ins/del ATTG (rs28362491), and IL-4 −590 C/T (rs2243250), was performed using polymerase chain reaction-restriction fragment length polymorphism. Genotype/allele frequencies, odds ratios (OR), and associations with clinical periodontal parameters (probing pocket depth [PPD], clinical attachment loss [CAL], plaque index [PI], and gingival index [GI]) were analyzed. Gene-gene interactions and severity-based stratification were also evaluated. Statistical tests included χ², Fisher’s exact test, logistic regression (adjusted for confounders), and analysis of variance/Kruskal–Wallis (p<0.05).

Results: Individual polymorphisms in TLR2, TLR4, NF-κB, and IL-4 showed no statistically significant independent association with periodontitis susceptibility (all p>0.05). However, combined genotype analysis revealed strong synergistic effects: Carriers of variant alleles in both TLR2 and TLR4 showed significantly increased risk (OR=2.84, 95% confidence interval [CI]: 1.52–5.34, p=0.001). Combined NF-κB del/del+IL-4 TT genotypes demonstrated the strongest association (OR=3.42, 95% CI: 1.68–6.94, p<0.001). These associations remained significant after adjustment for age, gender, smoking, diabetes, and socioeconomic status. Risk allele carriage (A in TLR2, T in TLR4, del in NF-κB, and T in IL-4) increased in a dose-dependent manner with disease severity (mild → moderate → severe; all trend p<0.05). Individuals with risk genotypes consistently exhibited significantly higher values of PPD, CAL, PI, and GI compared to reference genotypes (all p≤0.041).

Conclusion: While individual polymorphisms in TLR2, TLR4, NF-κB, and IL-4 genes do not show significant independent associations with chronic periodontitis in this population, their combined presence markedly increases disease susceptibility and is associated with greater clinical severity. These findings support a polygenic, synergistic genetic contribution to periodontitis risk and progression, highlighting the importance of gene-gene interactions in periodontal pathogenesis. Larger multicenter studies and functional analyses are warranted to validate these observations and explore potential for personalized risk stratification.