Mice immunized with CSFV G1.1 E2 glycoprotein presented significantly higher NA titers (average 1:10,240 dilution) against LPC/AHRI strain (G 1.1) infection than the TD/96/TWN strain (G 2.1a) (average dilution 1:640) and 94.4/IL/94/TWN strain (G 3.4) (average dilution 1:640) in sera. This evidence concerns the gene XK and infection.