Pan-HSV-2 IgG Antibody in Vaccinated Mice and Guinea Pigs Correlates with Protection against Herpes Simplex Virus 2
Figure 4
Pan-HSV-2 IgG levels correlate with protection against vaginal HSV-2 challenge in guinea pigs.
(A) Design of guinea pig vaccine-challenge experiment. Guinea pigs were immunized in their right, rear footpads on Day 0 with gD-2, culture medium (mock), HSV-2 0ΔNLS, or HSV-2 MS, as described in the Results (n = 5 per group). Guinea pigs immunized with HSV-2 MS received 1 mg/ml acyclovir in drinking water from Days 0 to 20 post-immunization to restrain the pathogenesis of a primary exposure to wild-type HSV-2. All guinea pigs were boosted in their left, rear footpads on Day 30 with an equivalent, booster immunization; MS-immunized guinea pigs did not receive acyclovir during the secondary boost. On Day 75, blood was harvested, and on Day 90, guinea pigs were challenged with 2×106 pfu per vagina of wild-type HSV-2 MS. (B) Mean ± sem pfu of HSV-2 shed per vagina between Days 1 and 8 post-challenge in guinea pigs that were naïve (n = 5) or were immunized with gD-2+ alum/MPL (n = 4), HSV-2 0ΔNLS (n = 5), or an acyclovir (ACV)-restrained HSV-2 MS infection (n = 5). A single asterisk (*) denotes p<0.05 and a double asterisk (**) denotes p<0.0001 that HSV-2 MS vaginal shedding was equivalent to naïve guinea pigs on that day, as determined by one-way ANOVA and Tukey’s post hoc t-test. (C) For each guinea pig (one symbol per animal), the average amount of infectious HSV-2 shed on Days 1, 2, 3, 4, 6, and 8 post-vaginal challenge (y-axis) was plotted as a function of pre-challenge pan-HSV-2 IgG levels observed in the same guinea pig (x-axis). The solid black line represents the best-fit linear regression model, y = 3.77–0.95x, for these 19 matched datum pairs. (D) Mean ± sem of log (pan-HSV-2 IgG) in each immunization group is plotted on the x-axis versus mean ± sem vaginal HSV-2 shedding on the y-axis. The solid black line represents the best-fit linear regression model, y = 3.77–0.95x, for these 4 matched averages (r2 = 0.98). Groups of immunized guinea pigs that exhibited a significant reduction in vaginal HSV-2 shedding relative to naïve guinea pigs are indicated by a single asterisk (*; p<0.05) or double-asterisk (**; p<0.001), as determined by one-way ANOVA and Tukey's post-hoc t-test. (E) The worst case of perivaginal disease in each group of naïve or immunized guinea pigs on Day 7 post-challenge. Survival frequency refers to the frequency with which animals in each immunization group survived until Day 30 post-challenge.