Distribution of LDV MFI median fluorescence values of serum samples (n = 8 per group) from sham (filled circles) and LDV (open circles) -inoculated (A) Swiss Webster, (B) C57BL/6, and (C) BALB/c female mice at 2, 4, 8, and 12 wk after infection. MFI fluorescence values greater than 2500 were considered positive for antiLDV antibody.