Interleukin - 1 Polymorphisms And Chronic Periodontitis In A Rural Kenyan Population

Abstract

Susceptibility to Chronic periodontitis (CP) has been associated with genetic polymorphisms in the proinflammatory cytokine, interleukin - 1 (IL - 1A and IL - 1B) isoforms but little is known about their role in rural Africans. Therefore, the aim of this study was to resolve the association between genetic polymorphisms in IL - 1A and IL - 1B isoforms and chronic periodontitis in the Taita people of Kenya. Methods: This was a case - control study. After informed consent, a clinical examination was then conducted which included assessment of dental plaque, gingival inflammation, pocket depths and gingival recession. Buccal swab samples were then obtained. Deoxyribonucleic acid (DNA) was isolated from the swabs using QIAamp DNA purification protocol followed by polymerase chain reaction (PCR) amplification using specific primers to IL - 1A (rs 1800587(- 889) & rs17561 (+48 45)) and IL - 1B (rs 16944 (- 511) & rs 11443624 (+3954). The amplicons were digested using Nco1, Fnu4H1, Ava1 and Taq1 respectively. Restriction fragment length polymorphisms (RFLP) were recorded. Association analyses of the RFLP and clinical data were carried out. Results: No deviation from the Hardy Weinberg equilibrium was observed. Carriage of allele2 at IL - 1B +3954 (i.e. combination of ‘2 - 2’ or‘1 - 2’ at locus +3954) was associated with CP in the Taita participants (OR = 1.94, 95%CI=1.01 - 3.70, p=0.045). There were no confounders or effect modifiers in the Taita participants and no association with severity of CP was observed in this population. None of the composite genotypes were associated with CP in the Taita participants. Haplotype 3 (i.e. allele1 at all the four loci) was significantly associated with CP amongst the Taita (O R=2.4, 95%CI=1.1 - 5.14, p=0.022). Conclusion: The significant association of allele2 at IL - 1B +3954 with CP in the Taita participants confirmed the importance of this genotype in disease pathogenesis. Keywords: chronic periodontitis, IL -1 polymorphisms, Rural Kenya, Taita