Virus titer in blood and brain from infected C3H/HeJ and C3H/CaJ mice. The sera and brain suspensions from three mice of C3H/HeJ as well as C3H/CaJ mice were titrated in vero E6 cells. Virus concentration was determined by end point dilution assay and reciprocal of highest dilution which showing 50% cell lysis was considered end point. The TCID50 per 100 μL was calculated by Reed and Munch formula. Each point in line graph represents mean virus titer of three mice.