Interleukin-10 and tumour necrosis factor alpha promoter region polymorphisms and susceptibility to urogenital schistosomiasis in young Zimbabwean children living in Schistosoma haematobium endemic regions

Abstract

Background: Host genetic factors can influence susceptibility, morbidity and mortality from schistosomiasis. The study explored the association between single nucleotide polymorphisms (SNPs) in interleukin-10 (IL-10) and tumour necrosis factor alpha (TNF-α) promoter regions and susceptibility to Schistosoma haematobium infection.

Methods: Urine specimens were collected from 361 primary school children aged 5-15 years from schistosomiasis endemic areas of Manicaland and Mashonaland central provinces. Schistosoma haematobium was diagnosed using the urine filtration method. Only 272 participants provided adequate blood for genotyping. Genotyping was performed using the amplification refractory mutation system-polymerase chain reaction. The association between IL-10 and TNF-α SNPs and S. haematobium infection was analysed using the chi-square test.

Results: Schistosoma haematobium infection was confirmed in 26.8% of the participants. No significant difference in S. haematobium prevalence between men (51.6% of those infected) and women (48.4%) (χ² = 0.008, df = 1, p = 0.928) was observed. The total IL-10 -1082 G, IL-10 -819 C and TNF-α -308G allele distribution between S. haematobium infected and uninfected participants was 50.7% and 51.5% (χ² = 0.025, df = 1, p = 0.87), 54.3% and 60.6% (χ² = 1.187, df = 1, p = 0.187) and 82.1% and 80.9% (χ² = 0.099, df = 1, p = 0.753), respectively, and the differences were not significant.

Conclusion: Interleukin-10 -1082 G/A, IL-10 -819 C/T and TNF-α -308 G/A SNPs were not significantly associated with susceptibility to S. haematobium infection. The prevalence of schistosomiasis is still in the moderate range and is similar in boys and girls.

Keywords: IL-10; S. haematobium; TNF-α; cytokine polymorphisms; ssociations.

FIGURE 1

Amplicons for interleukin-10 -819 C/T single nucleotide polymorphism. Lane M shows 100 base pair (bp) molecular marker. The 426 bp fragments correspond to the internal control (the human growth hormone gene). The 233 bp fragments were specific for C and T alleles of IL-10 -819 C/T single nucleotide polymorphisms. Lanes labelled 3, 6 and 7 show heterozygous CT genotypes. Lanes labelled 1 and 4 show homozygous CC and TT genotypes, respectively.

FIGURE 2

Amplicons for interleukin-10 -1082 G/A single nucleotide polymorphism. Lane M shows 100 base pair (bp) molecular marker. The 426 bp fragments correspond to the internal control. The 258 bp fragments were specific for G and A alleles of interleukin-10 -1082 G/A single nucleotide polymorphisms. Lanes labelled 1, 2 and 4 show heterozygous GA genotype. Lanes labelled 5, 6 and 7 show homozygous AA genotype.

FIGURE 3

Amplicons for tumour necrosis factor-alpha -308 G/A single nucleotide polymorphism. Lane M shows 100 base pair (bp) molecular marker. The 426 bp fragments correspond to the internal control. The 267 bp fragments were specific for G and A alleles of tumour necrosis factor-alpha -308 G/A single nucleotide polymorphisms. Lane 5 shows heterozygous GA genotype. Lanes labelled 6 and 7 show homozygous GG genotype.