Dengue vaccine breakthrough infections reveal properties of neutralizing antibodies linked to protection

Abstract

The 4 serotypes of dengue virus (DENV1-4) are mosquito-borne flaviviruses that infect humans. Live attenuated tetravalent DENV vaccines are at different phases of clinical testing. DENV vaccine developers have relied on neutralizing antibodies (NAbs) as a correlate of protection. A leading tetravalent vaccine (Dengvaxia) stimulated NAbs to the 4 DENV serotypes, yet overall vaccine efficacy was low in children who were DENV seronegative at baseline before vaccination. We compared the properties of (a) NAbs induced by WT DENV1 or DENV3 infections, which are strongly correlated with protection from repeat infections, and (b) NAbs induced by Dengvaxia in individuals who subsequently experienced DENV1 or DENV3 breakthrough infections. WT infections induced NAbs that recognized epitopes unique (type specific) to each serotype, whereas the vaccine stimulated qualitatively different NAbs that recognized epitopes conserved (crossreactive) between serotypes. Our results indicate that, among children who were DENV-seronegative at baseline, unbalanced replication of the DENV type 4 vaccine component in the tetravalent vaccine stimulates Abs capable of crossneutralizing DENV1 and DENV3 in vitro, but not protecting in vivo. In DENV-seronegative individuals who are vaccinated, we propose that type-specific NAbs are a better correlate of protection than total levels of NAbs.

Trial registration: ClinicalTrials.gov NCT01373281 NCT01374516.

Keywords: Adaptive immunity; Immunoglobulins; Vaccines; Virology.

Conflict of interest statement

Conflict of interest: MB, JMM, and AM are employees of Sanofi Pasteur, which developed Dengvaxia.

Figures

Figure 1. Ab responses following primary DENV1 or DENV3 infection.

Convalescent sera from people exposed to primary DENV1 (A) or DENV3 (B) infections were tested for NAb before (Control depleted) and after removal of total DENV Abs (Complete Ab depleted) or DENV serotype CR Abs (CR Ab depleted). Total Abs were depleted using DENV serotype responsible for infection as the depleting antigen (DENV1 or DENV3), and CR Abs were removed using a mix of antigen from heterologous DENV serotypes (DENV2 and DENV4 antigens for DENV1 immune sera and DENV1, DENV2, and DENV4 antigens for DENV3 immune sera). Levels of DENV1 or 3 neutralizing Abs were not significantly reduced by the removal of CR Abs. Friedman’s 1-way ANOVA was used to establish statistical significance.

Figure 2. Vaccine-induced Ab responses in children who experienced DENV1 breakthrough infections.

Vaccine responses to DENV1 (A) and DENV4 (B) were analyzed in baseline seronegative children who received Dengvaxia and subsequently experienced DENV1 (n = 15) breakthrough infections. (A) DENV1 NAb responses after vaccination were measured without depleting any Ab (Control depleted), after removal of all DENV1-binding Abs (Complete Ab depleted with DENV1 antigen), and after removal of CR Ab (CR Ab depleted using a mix of DENV2 and DENV4 antigens). (B) DENV4 NAb responses after vaccination were measured without depleting any Ab (Control depleted), after removal of all DENV4-binding Ab (Complete Ab depleted with a mix of DENV2 and DENV4 antigens), and after removal of CR Ab (CR Ab depleted using DENV1 antigen). (C) The data were also analyzed to compare the percentages of DENV1 and DENV4 TS NAbs in the children after vaccination. Friedman’s 1-way ANOVA test (A and B) or Wilcoxon’s signed ranks test (C) was used to establish statistical significance.

Figure 3. Vaccine-induced Ab responses in children who experienced DENV3 breakthrough infections.

Vaccine responses were analyzed in baseline seronegative children who received Dengvaxia and subsequently experienced DENV3 (n = 18) breakthrough infections. (A) DENV3 NAb responses after vaccination were measured without depleting any Ab (Control depleted), after removal of all DENV3-binding Abs (Complete Ab depleted with DENV3 antigen), and after removal of CR Ab (CR Ab depleted using a mix of DENV1, DENV2, and DENV4 antigens). (B) DENV4 NAb responses after vaccination were measured without depleting any Ab (Control depleted), after removal of all DENV4-binding Abs (Complete Ab depleted with a mix of DENV1, DENV2, and DENV4 antigens), and after removal of CR Ab (CR Ab depleted using DENV3 antigen). (C) The data were also analyzed to compare the percentages of DENV3 and DENV4 TS NAbs in the children after vaccination. Friedman’s 1-way ANOVA test (A and B) or Wilcoxon’s signed ranks test (C) was used to establish statistical significance.

Figure 4. Dengvaxia-induced Ab responses in children with no preexisting immunity to DENVs.

Dengvaxia recipients irrespective of subsequent outcome during CYD-TDV clinical trials were tested to determine levels of total and TS DENV1 (A), DENV3 (B), and DENV4 (C) NAbs. Wilcoxon’s signed ranks test was used to establish statistical significance. The data were also analyzed to compare the percentages (D) of vaccine-induced DENV1, DENV3, and DENV4 TS NAbs. Kruskal-Wallis test was used to compare Ab responses between serotypes. Supplemental Table 3 displays the DENV antigen combinations used for depletion to measure levels of TS NAbs to each serotype.