A Randomized, Double-Blinded, Placebo-Controlled, Phase 1 Study of a Replication-Defective Herpes Simplex Virus (HSV) Type 2 Vaccine, HSV529, in Adults With or Without HSV Infection

Abstract

Background: Herpes simplex virus 2 (HSV2) causes genital herpes in >400 million persons worldwide.

Methods: We conducted a randomized, double-blinded, placebo-controlled trial of a replication-defective HSV2 vaccine, HSV529. Twenty adults were enrolled in each of 3 serogroups of individuals: those negative for both HSV1 and HSV2 (HSV1-/HSV2-), those positive or negative for HSV1 and positive for HSV2 (HSV1±/HSV2+), and those positive for HSV1 and negative for HSV2 (HSV1+/HSV2-). Sixty participants received vaccine or placebo at 0, 1, and 6 months. The primary end point was the frequency of solicited local and systemic reactions to vaccination.

Results: Eighty-nine percent of vaccinees experienced mild-to-moderate solicited injection site reactions, compared with 47% of placebo recipients (95% confidence interval [CI], 12.9%-67.6%; P = .006). Sixty-four percent of vaccinees experienced systemic reactions, compared with 53% of placebo recipients (95% CI, -17.9% to 40.2%; P = .44). Seventy-eight percent of HSV1-/HSV2- vaccine recipients had a ≥4-fold increase in neutralizing antibody titer after 3 doses of vaccine, whereas none of the participants in the other serogroups had such responses. HSV2-specific CD4+ T-cell responses were detected in 36%, 46%, and 27% of HSV1-/HSV2-, HSV1±/HSV2+, and HSV1+/HSV2- participants, respectively, 1 month after the third dose of vaccine, and CD8+ T-cell responses were detected in 14%, 8%, and 18% of participants, respectively.

Conclusions: HSV529 vaccine was safe and elicited neutralizing antibody and modest CD4+ T-cell responses in HSV-seronegative vaccinees.

Clinical trials registration: NCT01915212.

Keywords: HSV2; Herpes simplex; genital herpes; vaccine.

Published by Oxford University Press for the Infectious Diseases Society of America 2019.

Figures

Figure 1.

Screening, enrollment, vaccination, and follow-up. Participants in each serogroup were randomized to receive vaccine or placebo in a 3:1 ratio. Initially, 4 participants eligible for the group that was positive or negative for herpes simplex virus type 1 (HSV1) and positive for HSV2 (HSV1±/HSV2+) were enrolled and dosed with the first dose. After a 4-week safety assessment period, enrollment was open to all 3 serogroups. After dosing 4 participants each in the group positive for HSV1 and negative for HSV2 (HSV1+/HSV2−) and the group negative for both HSV1 and HSV2 (HSV1−/HSV2−) and a 7-day safety assessment period, enrollment continued into all 3 groups. Overall, 97% of participants received all 3 doses of vaccine or placebo. Blood specimens were collected on the day before each injection, 1 day after the first dose, 7 days after each dose, 30 days after the third dose, and 360 days after day 0 for evaluation of immune responses. PFU, plaque-forming units. aTwo participants did not receive the third dose of vaccine and missed several study visits because of unplanned pregnancy.

Figure 2.

Herpes simplex virus type 2 (HSV2)–specific neutralizing antibody responses. A, Individual participant responses in each serogroup, comparing the titer at baseline (day 0) to the titer 30 days after the third dose of vaccine or placebo (day 210). Short horizontal black bars represent the log10 geometric mean titer (GMT) in each serogroup. P values were calculated using a paired t test. B, The log10 GMT for each serogroup over time. Arrows indicate vaccine administration days. Horizontal dashed lines indicate the lower limit of detection. Serogroups comprised individuals negative for both HSV1 and HSV2 (HSV1−/HSV2−), those positive or negative for HSV1 and positive for HSV2 (HSV1±/HSV2+), and those positive for HSV1 and negative for HSV2 (HSV1+/HSV2−). *P < .05, based on a paired t test for individual subject titers, compared with day 0.

Figure 3.

Herpes simplex virus (HSV) glycoprotein D (gD)–specific antibody responses. A, Individual participant responses, comparing the titer at baseline (day 0) to the titer at day 210, 1 month after the third dose. Short horizontal bars represent the log10 geometric mean for each serogroup. B, The log10 geometric mean for each serogroup over time. Horizontal dotted-dashed lines represent the mean of the responses of a pool of sera that were negative for HSV type 2 (HSV2) neutralizing activity. Arrows indicate vaccine administration days. Serogroups comprised individuals negative for both HSV1 and HSV2 (HSV1−/HSV2−), those positive or negative for HSV1 and positive for HSV2 (HSV1±/HSV2+), and those positive for HSV1 and negative for HSV2 (HSV1+/HSV2−). Geometric means for the HSV1–/HSV2– group were 4897 light units (LU)/uL (on day 0), 63 095 LU/uL (on day 60), 31 622 LU/uL (on day 180), 398 107 LU/uL (on day 210), and 251 188 LU/uL (on day 360). gD antibody levels were determined by luciferase immunoprecipitation systems. *P < .05, based on a paired t test for individual subject titers, compared with day 0.

Figure 4.

Herpes simplex virus type 2 (HSV2)–specific T-cell responses after 3 doses of vaccine or placebo in participants negative for both HSV1 and HSV2 (HSV1–/HSV2–). A, Results of pairwise testing of interferon γ (IFN-γ) enzyme-linked immunospot (ELISPOT) findings to determine changes in CD8+ T-cell responses between baseline (day 0) and after the third dose of HSV529 or placebo (day 210; left) and throughout the study period (right). B, Results of pairwise testing of IFN-γ ELISPOT findings to determine changes in CD4+ T-cell responses between baseline (day 0) and after the third dose of HSV529 or placebo (day 210; left) and throughout the study (right). For pairwise comparisons (left panels), each line represents paired samples from 1 subject, and short horizontal bars are medians. The Wilcoxon rank sum test (2-sided) was used to calculate P values. For time course analyses (right), symbols represent median net response ± interquartile range, and parametric testing with linear mixed models was used for analysis. Horizontal dashed lines indicate the threshold for a positive response. Arrows indicate vaccine administration days. NEG, negative; PBMC, peripheral blood mononuclear cell; SFC, spot-forming cell; TNTC, too numerous to count. *P < .05.

Figure 5.

Herpes simplex virus type 2 (HSV2)–specific T-cell responses after 3 doses of vaccine or placebo in HSV-seropositive participants. A, Results of pairwise testing of interferon γ (IFN-γ) enzyme-linked immunospot (ELISPOT) findings to determine changes in CD8+ T-cell responses between baseline (day 0) and after the third dose of HSV529 or placebo (day 210; left) and throughout the study period (right) among individuals who were positive or negative for HSV1 and positive for HSV2 (HSV1±/HSV2+) and those who were positive for HSV1 and negative for HSV2 (HSV1+/HSV2−). B, Results of pairwise testing of IFN-γ ELISPOT findings to determine changes in CD4+ T-cell responses to UV-inactivated HSV2 between baseline (day 0) and after the third dose of HSV529 or placebo (day 210; left) and throughout the study (right) in HSV1±/HSV2+ and HSV1+/HSV2− serogroups. For pairwise comparisons, each line represents samples from 1 subject, and short horizontal bars are medians. The rank sum test (2-sided) was used to calculate P values. For time courses, symbols represent median responses (interquartile ranges), and parametric testing with linear mixed models was used for analysis. Horizontal dashed lines indicate the threshold for a positive response. Arrows indicate vaccine administration days. NEG, negative; PBMC, peripheral blood mononuclear cell; SFC, spot-forming cell; TNTC, too numerous to count. *P < .05.

Figure 6.

COMPASS functionality scores of T-cell activation markers in response to antigen stimulation among individuals who were positive or negative for HSV1 and positive for HSV2 (HSV1±/HSV2+) and those who were positive for HSV1 and negative for HSV2 (HSV1+/HSV2−). A, Functionality score changes within individuals between day 0 (baseline) and day 210. Unadjusted P values were calculated using 1-sided Wilcoxon signed rank tests. B, Increase in polyfunctional CD4+ T cells (ie, those expressing CD40L, interferon γ [IFN-γ], interleukin 2 [IL-2], and tumor necrosis factor [TNF-α]) between days 0 and 210. The P value is adjusted for multiple comparisons among all 16 possible Boolean subsets, using the Bonferroni method. Short, horizontal black bars represent median values. Day 0, before vaccination (ie, baseline); day 210, 1 month after the third dose of vaccine.