We then subjected Vero cells to pretreatment with IFN-α2 at a concentration of 100 or 50 pg/ml 24 h before infection in the presence or absence of serum with (n = 14) or without (n = 5) auto-Abs at a dilution of 1:10 or 1:100 using a previously titrated 50% tissue culture infectious dose (TCID50) of WNV diluted 1:100. This evidence concerns the gene IFNA2 and infection.