Associations of Interleukin-1 Polymorphisms with Chronic Periodontitis in Two Different Kenyan Ethnic Groups: A Case Control Study.

OBJECTIVE: The aim of this study was to investigate the association between IL-1ß and IL-1α isoforms with chronic periodontitis in two Kenyan ethnic groups, Taitas and Swahilis. METHODS: A case-control study in which participants were assessed for dental plaque, gingival inflammation, pocket depth and gingival recession after informed consent. Buccal swab samples were obtained and deoxyribonucleic acid was isolated from the swabs using QIAamp DNA purification protocol followed by polymerase chain reaction amplification using specific primers to IL-1 α rs1800587 (-889) and rs17561 (+4845) and IL-1ß (rs16944 (-511) and rs11443624 (+3954). Restriction fragment length polymorphisms were recorded and association with clinical data was assessed. RESULTS: Three hundred and ninety participants were recruited; four loci (-511, -889, +3953 and +4845) were analyzed per subject, equivalent to 1560 analysis events. No deviation from Hardy Weinberg equilibrium 1df was observed. Frequency of allele 2 at IL-1ß +3954 was associated with chronic periodontitis in Taitas (OR = 1.94, 95% CI = 1.01 - 3.70, p = 0.045), whereas frequency of allele 1 at IL-1α -889 was associated with chronic periodontitis in Swahilis (OR = 3.16, 95% CI = 1.644 - 6.083, p less than 0.001). Allele 1 at locus IL-1α -889 was also associated with mild, (OR = 5.2, 95% CI = 1.445 - 18.71, p = 0.005), moderate (OR = 4.51, 95% CI = 2.08 - 9.79, p less than 0.001) and severe disease (OR = 2.19, 95% CI = 1.013 - 4.738, p = 0.042) in Swahilis. Haplotype 3 (allele 1 at all four loci) was significantly associated with chronic periodontitis in Taitas (OR = 2.4, 95% CI = 1.1 - 5.14, p = 0.022) and Swahilis (OR = 4.2, 95%CI = 1.35 - 13.3, p = 0.008). CONCLUSIONS: This study has shown that in the African population of Bantu origin, the two polymorphisms associated with chronic periodontitis are IL-1ß +3954 in Taitas and IL-1α-889 in Swahilis. Additionally, haplotype 3 was associated with chronic periodontitis in both ethnic groups.