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Abstract
Toll-like receptor 9 (TLR9) recognizes non-methylated viral CpG-containing DNA and serves as a pattern recognition receptor that signals the presence of human cytomegalovirus (HCMV). Here, we present the genotype distribution of single-nucleotide polymorphisms (SNPs) of the TLR9 gene in infants and the relationship between TLR9 polymorphisms and HCMV infection. Four polymorphisms (-1237T/C, rs5743836; -1486T/C, rs187084; 1174G/A, rs352139; and 2848C/T, rs352140) in the TLR9 gene were genotyped in 72 infants with symptomatic HCMV infection and 70 healthy individuals. SNP genotyping was performed by using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Digested fragments were separated and identified by capillary electrophoresis. The HCMV DNA copy number was measured by a quantitative real-time PCR assay. We found an increased frequency of heterozygous genotypes TLR9 -1486T/C and 2848C/T in infants with HCMV infection compared with uninfected cases. Heterozygous variants of these two SNPs increased the risk of HCMV disease in children (P = 0.044 and P = 0.029, respectively). In infants with a mutation present in at least one allele of -1486T/C and 2848C/T SNPs, a trend towards increased risk of cytomegaly was confirmed after Bonferroni’s correction for multiple testing (Pc = 0.063). The rs352139 GG genotype showed a significantly reduced relative risk for HCMV infection (Pc = 0.006). In contrast, the -1237T/C SNP was not related to viral infection. We found no evidence for linkage disequilibrium with the four examined TLR9 SNPs. The findings suggest that the TLR9 -1486T/C and 2848C/T polymorphisms could be a genetic risk factor for the development of HCMV disease.
Highlights
Human cytomegalovirus (HCMV), a member of the Betaherpesvirinae subfamily of herpesviruses, is a ubiquitous pathogen with a seroprevalence of 45–100% [1]
In the group of infants without HCMV infection, the frequencies of genotypes at all Toll-like receptor 9 (TLR9) single-nucleotide polymorphisms (SNPs) were in Hardy-Weinberg equilibrium (HWE) (P > 0.05; Table 4)
We demonstrated that the heterozygous genotype of TLR9 -1486T/C and 2848C/ T occurred more frequently in infants with HCMV infection than in uninfected cases
Summary
Human cytomegalovirus (HCMV), a member of the Betaherpesvirinae subfamily of herpesviruses, is a ubiquitous pathogen with a seroprevalence of 45–100% [1]. Primary HCMV infection is usually asymptomatic in healthy individuals and is followed by a persistent infection. HCMV is a major reason of multiorgan disease in immunocompromised patients and a leading cause of congenital infection, occurring in 0.5–2% of pregnancies in the United States and Europe [2, 3]. Approximately 10–15% exhibit signs and symptoms of disease at birth, and these symptomatic infants have an increased risk for sensorineural hearing loss and central nervous system damage [4, 5]. The factors that dictate whether HCMV infection is asymptomatic or symptomatic are not clear. Innate immunity plays a crucial role in preventing the acquisition of HCMV infections, whereas its failure may contribute to an increased risk of infection. It is suggested that variations in the genes that modulate innate immune responses, including TLRs genes, may result in distinct clinical presentations of infection
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