FIG 6.

Humoral immune response. (A) Virus neutralization capacity of serum from immunized animals, with 1 neutralizing unit defined as the concentration of serum that prevents 50% CPE on Vero cell monolayers (MOI of ≈1.5; n = 18 to 20 mice per group; 5 independent experiments). Neutralizing titers were not observed with serum obtained from naive mice. The dotted line indicates the level of detection (1:12.5; assay threshold, 1:3,200). Significance thresholds were determined by Student's t tests comparing 0ΔNLS to gD-2 samples and are indicated as follows: *, P < 0.01; **, P < 0.001. (B) Representative Western blots showing the breadth of viral proteins recognized in serum from immunized and naive mice. Lysates were resolved on polyacrylamide gels and probed with a 1:500 dilution of serum. The breadth of humoral responses was based on the number of reactive bands on lysates from uninfected (UI) or HSV-1 (McKrae)-infected Vero cells. (C) Western blots showing specificity of gD-2 and 0ΔNLS serum. Cell lysates from UI cells or cells infected with wild-type HSV-1 (KOS), HSV-1 deficient in gD (ΔgD), wild-type HSV-2 (strain MS), or TR-gD-2 cells expressing gD-2 (gD-2⁺) were resolved on polyacrylamide gels and probed with serum from gD-2- or 0ΔNLS-vaccinated mice at a 1:5,000 dilution. MW, molecular weight (in thousands).