This study aimed to assess the relationship of OAS2 rs739901 5＇-flanking C/A polymorphisms with the susceptibility to Enterovirus-71 （EV71） infection. We investigated 294 hand-foot-mouth disease （HFMD） Chinese children with EV71 infection （165 mild cases and 129 encephalitis cases）. The improved multiplex ligation detection reaction （iMLDR） technique was used to test the genotypes. In EV71-infected patients, the CA genotype distribution （P=0.007）, A allele frequency （OR 1.32, 95% CI 1.0-1.7, P=0.034） and CA＋AA carriage frequency （P=0.003） of OAS2 rs739901 5＇-flanking were obviously elevated as compared with controls, but there were no statistically significant differences between mild cases and encephalitis cases. In EV71-infected patients, the counts of white blood cells （P=0.034） and blood glucose concentrations （P=0.042） were raised in A carriers （CA＋AA）. Among different genotypes of encephalitis cases, the contents of cerebrospinal fluid （CSF） showed no significant differences. IFN-7 levels in EV71-infected patients were higher than those in controls （mild group vs. control group, P〈0.01; encephalitis group vs. control group, P〈0.001）. In encephalitis cases, IFN-7 levels were reduced （P〈0.05） in A carriers compared to CC genotype, however, there were no significant differences between genotypes CA and AA （ P=0.226）. These findings suggest that OAS2 rs739901 5＇-flanking C/A genetic polymorphisms involve the susceptibility to EV71 infection, and A allele might be a risk factor of the susceptibility to EV-71 infection.
