Polymorphisms in the oligoadenylate synthetase gene cluster and its association with clinical outcomes of dengue virus infection.

Oligoadenylate synthetases (OAS) play an important role in the immune response against dengue virus. Single nucleotide polymorphisms (SNPs) in the OAS genes are known to affect OAS activity and are associated with outcome of viral infections. Polymorphisms in the OAS1 (rs1131454 and rs10774671), OAS3 (rs2285932 and rs2072136) and OAS2 (rs15895 and rs1732778) genes were studied using PCR followed by restriction fragment length polymorphism methods in 109 patients hospitalized for dengue (DEN) and 105 healthy controls (HCs) who have no documented evidence of symptomatic dengue. The two locus haplotype of OAS2 G-G was significantly higher in all patient groups [DEN vs. HCs, P=0.0041, P corrected (Pc)=0.012, Odds ratio (OR) 1.73 95% CI 1.16-2.59] while the four locus haplotype of OAS3-OAS2 C-G-A-G was significantly lower in all dengue patient groups [DEN vs. HCs, P=0.0054, Pc=0.0486, OR 0.09, 95% CI 0.00-0.64] compared to controls. When the six locus haplotypes involving OAS1, OAS3 and OAS2 polymorphisms were analyzed and compared, the frequency of the haplotype A-A-C-A-G-G was significantly higher [P=0.0267, Pc=0.486, OR 2.34, 95% CI 1.08-4.91] and the frequency of the haplotype A-A-C-G-G-A was significantly lower in DHF cases [P=0.014, Pc=0.252, OR 0.12, 95% CI 0.01-0.85] compared to healthy controls. The results suggest that OAS1-OAS3-OAS2 haplotypes are associated with differential susceptibility to clinical outcomes of dengue infection.