An adjuvanted, tetravalent dengue virus purified inactivated vaccine candidate induces long-lasting and protective antibody responses against dengue challenge in rhesus macaques

Abstract

The immunogenicity and protective efficacy of a candidate tetravalent dengue virus purified inactivated vaccine (TDENV PIV) formulated with alum or an Adjuvant System (AS01, AS03 tested at three different dose levels, or AS04) was evaluated in a 0, 1-month vaccination schedule in rhesus macaques. One month after dose 2, all adjuvanted formulations elicited robust and persisting neutralizing antibody titers against all four dengue virus serotypes. Most of the formulations tested prevented viremia after challenge, with the dengue serotype 1 and 2 virus strains administered at 40 and 32 weeks post-dose 2, respectively. This study shows that inactivated dengue vaccines, when formulated with alum or an Adjuvant System, are candidates for further development.

Figure 1.

NAb responses to adjuvanted and non-adjuvanted TDENV PIV formulations containing one of three different antigen doses. NAb titers were measured by an ELISA-based MN₅₀ assay in serum samples from monkeys who received two doses, 1 month apart, of either an adjuvanted or non-adjuvanted TDENV PIV formulation containing (A) 2.0, (B) 0.5, or (C) 0.125 μg per serotype per dose or PBS (N = 4 per group). Sera for the selected time points shown were obtained before (day 30) and 1, 3, or 4 months post-second immunization (days 60, 120, and 150, respectively). The dashed line represents the cutoff value for a positive result. CI = confidence interval; D = day.

Figure 2.

NAb responses to adjuvanted TDENV PIV formulations containing 0.5 μg antigen per serotype. NAb titers were measured by an ELISA-based MN₅₀ assay in serum samples from monkeys who received two doses, 1 month apart, of either an adjuvanted TDENV PIV formulation (0.5 μg per serotype per dose), or PBS. Sera for the selected time points shown were obtained before (day 28) and 4, 12, 20, and 40 weeks after the second immunization (days 56, 168, and 308, respectively; N = 10 per group on days 28, 56, and 168 and N = 5 per group on day 308). The dashed line represents the cutoff value for a positive result. CI = confidence interval; D = day.

Figure 3.

Circulating DENV genome (RNAemia) in serum post-challenge with either DENV-1 or DENV-2. Serum samples from monkeys (N = 5 per group) who received an adjuvanted TDENV PIV formulation (0.5 μg per type per dose) or PBS were obtained daily post-challenge with either (A) DENV-1 or (B) DENV-2 and tested for the presence of viral RNA (RNAemia) by RT-PCR assay. The dashed line represents the limit of quantitation (i.e., 360 GEQ/mL; therefore, values below this limit are approximations).

Figure 4.

NAb responses before and after viral challenge with DENV-1 or DENV-2. NAb titers were measured by an ELISA-based MN₅₀ assay in serum samples from monkeys (N = 5 per group) who received either an adjuvanted TDENV PIV formulation (0.5 μg per type per dose) or PBS, and were challenged at 40 (day 308) or 32 (day 252) weeks post-second vaccination with either (A) DENV-1 or (B) DENV-2, respectively. Sera were obtained at the days of challenge and 1 month later. The dashed line represents the cutoff value for a positive result. CI, confidence interval; D = day