Figure 4.

Neutralization of the gBΔ2–30 mutant. (A) Wild-type (WT) and gB-NT deletion virions were incubated with the gB-NT-specific neutralizing mAb MG-2C10, then assayed for infectivity on BHK-21 cells. Equivalent data were obtained in two further experiments. (B) Sera from mice infected with wild-type (WT) or gBΔ2–30 MuHV-4 were used to neutralize WT or gBΔ2–30 virions for BHK-21 cell infection. Each of the six serum samples is from one mouse. Equivalent data were obtained in four further experiments, using different immune sera. We compared titers by χ² test (scoring as more or less than the interpolated median) for all the sera at each dilution. In the experiment shown, five of six serum dilutions showed a significant difference in neutralization (P<0.05) between WT and gBΔ2–30 viruses. Each repeat experiment showed significant differences at more than half the dilutions tested. (C) Wild-type (WT) and gBΔ2–30 virions were exposed to different neutralizing mAbs, then assayed for infectivity on BHK-21 cells. BH-6B5 is gB specific but not gB-NT specific. Scoring the titer for each virus to the average for that dilution and then comparing the values for all the dilutions of an assay by χ² test showed that gH/gL-specific mAbs neutralized the gBΔ2–30 mutant significantly better than the wild type (P<0.002). Equivalent data were obtained in four further experiments. (D) Wild-type (WT) and gBΔ2–30 virions were exposed to sera from mice infected with WT or gL-deficient (gL⁻) MuHV-4. Both showed greater neutralization of the gBΔ2–30 mutant, but the difference was greater for wild-type-immune sera. (E) Equivalent results to (D) for five different immune sera in each group at a single serum dose (2.5 μl/1000 p.f.u. virus). Wild-type-immune sera showed a significant difference in neutralization between wild-type and gBΔ2–30 virions (P<0.002 by Student's t-test). The gL⁻-immune sera did not (P=0.14).