FIG. 3.

Phenotypic analysis of MVMi mutants selected in SCID mice. (A) Viruses selected in mice formed larger plaques and showed postentry resistance to PAb neutralization. Representative plaque sizes of NS2 mutants recovered from spleen homogenates of SCID mice are shown. Note the different sizes compared to that of the wt and the reduction in size upon PAb addition to the overlaid medium. The bottom panel shows the degree of postentry resistance. Shown are percentages of residual PFU after the addition of the indicated NU of PAb to the overlay medium. Bars show averages with standard errors for three independent experiments (the results for the L153M mutant are from one experiment). (B) Growth rates of NS2 mutants. NB324K cells were infected at an MOI of 0.01 with the indicated viruses in the absence (left) or presence (right) of the neutralizing PAb added to the medium, and the production of infectious virus in the cultures was monitored by a PFU assay. The results are representative of two experiments with similar outcomes.