Association of single nucleotide polymorphism rs3775291 in the coding region of the TLR3 gene with predisposition to tick-borne encephalitis in a Russian population.

Tick-borne encephalitis (TBE) is a central nervous system (CNS) disease caused by the neurotropic, positive-sense RNA virus, tick-borne encephalitis virus (TBEV). A possible association between predisposition to TBE in a Russian population and two polymorphisms, a 32bp deletion in the coding region of the chemokine receptor CCR5 gene and the rs3775291 single nucleotide polymorphism (SNP) (G/A, Leu412Phe) in exon 4 of the toll-like receptor TLR3 gene, was investigated. The genotypic and allelic frequencies of these polymorphisms were analyzed in 137 non-immunized TBE patients with different clinical manifestations, including fever (35), meningitis (62), and severe CNS disease (40), as well as in a control population (269 randomly selected Novosibirsk citizens). The frequencies of the TLR3 G allele and G/G homozygotes were significantly higher among the patients with TBE compared with the control group (P=0.029 and 0.037, respectively), especially among patients with severe disease (P=0.018 and 0.017, respectively). These results indicate that the G allele (within the G/G homozygous genotype) of the TLR3 rs3775291 SNP is associated with predisposition to TBE in the Russian population.