Evaluation of protection induced by a dengue virus serotype 2 envelope domain III protein scaffold/DNA vaccine in non-human primates

Abstract

We describe the preclinical development of a dengue virus vaccine targeting the dengue virus serotype 2 (DENV2) envelope domain III (EDIII). This study provides proof-of-principle that a dengue EDIII protein scaffold/DNA vaccine can protect against dengue challenge. The dengue vaccine (EDIII-E2) is composed of both a protein particle and a DNA expression plasmid delivered simultaneously via intramuscular injection (protein) and gene gun (DNA) into rhesus macaques. The protein component can contain a maximum of 60 copies of EDIII presented on a multimeric scaffold of Geobacillus stearothermophilus E2 proteins. The DNA component is composed of the EDIII portion of the envelope gene cloned into an expression plasmid. The EDIII-E2 vaccine elicited robust antibody responses to DENV2, with neutralizing antibody responses detectable following the first boost and reaching titers of greater than 1:100,000 following the second and final boost. Vaccinated and naïve groups of macaques were challenged with DENV2. All vaccinated macaques were protected from detectable viremia by infectious assay, while naïve animals had detectable viremia for 2–7 days post-challenge. All naïve macaques had detectable viral RNA from day 2–10 post-challenge. In the EDIII-E2 group, three macaques were negative for viral RNA and three were found to have detectable viral RNA post challenge. Viremia onset was delayed and the duration was shortened relative to naïve controls. The presence of viral RNA post-challenge corresponded to a 10–30-fold boost in neutralization titers 28 days post challenge, whereas no boost was observed in the fully protected animals. Based on these results, we determine that pre-challenge 50% neutralization titers of >1:6000 correlated with sterilizing protection against DENV2 challenge in EDIII-E2 vaccinated macaques. Identification of the critical correlate of protection for the EDIII-E2 platform in the robust non-human primate model lays the groundwork for further development of a tetravalent EDIII-E2 dengue vaccine.

Recent Developments in Recombinant Protein–Based Dengue Vaccines

“…This vaccine conferred protection to the vaccinated macaques upon challenge with dengue virus 2, whereas the control animals showed viremia. These results concluded that a neutralizing antibody titer (>1: 6000) provided sterilizing protection in immunized macaques ( 75 ).…”

A dose-response study in mice of a tetravalent recombinant dengue envelope domain III protein secreted from insect cells

“…Accumulating studies have proved that EDIII-based vaccine candidates can elicit specific neutralizing antibodies [38][39][40] Choosing only domain III rather than whole envelope protein could reduce the risk of ADE due to the lack of other non-neutralizing or cross-reactive epitopes. Hence, most of recent efforts have focused on utilization of EDIII to produce a subunit dengue vaccine [41][42][43]. We have constructed a tetravalent domain III in tandem using the Gly4SerGly4 linker, and testified its potential utility in the diagnosis of DENV infections with a high degree of sensitivity and specificity [41].…”

Engineering DNA vaccines against infectious diseases

“…Another physical method developed to deliver plasmids epidermally is the gene gun [95]. A particle-mediated epidermal delivery (PMED) gene gun was used in preclinical trials to deliver a DNA vaccine against the dengue virus in nonhuman primates.…”