Objective: To investigate the polymorphisms of interleukin-18(IL-18) gene promoters, and to disclose whether such polymorphisms are associated with susceptibility to chronic hepatitis B in Chinese Han population.
Methods: Using polymerase chain reaction with sequence specific primers method, the authors detected the single nucleotide polymorphisms of the promoter region of IL-18 gene at position -607C/A and -137G/C in 231 patients with chronic hepatitis B and 300 normal controls.
Results: The frequency of CC genotype in IL-18 gene promoter region at position -607 was 0.22(66/300) in normal controls and 0.27(62/231) in patients. The frequency of CA genotype was 0.53(160/300) in normal controls and 0.50(116/231) in patients. The frequency of AA genotype was 0.25(74/300) in normal controls and 0.23(53/231) in patients. The frequencies of -137GG, GC and CC genotype were 0.67, 0.30 and 0.03 in normal controls respectively; whereas in chronic hepatitis B patients the frequencies were 0.79, 0.19 and 0.02. The genotype frequency of -137GG in chronic hepatitis B groups was significantly higher than that in normal controls(chi2: 8.55, P=0.003), but the frequencies of -607C/-137C and -607A/-137C haplotypes in chronic hepatitis B groups were significantly lower than those in normal controls. The association between genotype of IL-18 promoter region polymorphisms and hepatitis B virus(HBV) copies showed that the frequency of -607AA genotype in high HBV-DNA copies groups was lower than that in low HBV-DNA copies groups(chi2: 6.03, P=0.014).
Conclusion: The polymorphisms of the promoter region of IL-18 gene at position -607C/A and -137G/C are correlated with chronic hepatitis B in Chinese Han population. The people with -137C allele in the promoter region of IL-18 gene may be protected against HBV infection, and the IL-18 -607AA genotype may be linked to HBV-DNA copy.