Enhancement of Tetravalent Immune Responses to Highly Conserved Epitopes of a Dengue Peptide Vaccine Conjugated to Polystyrene Nanoparticles

Babu Ramanathan,Yanqi Chan,Seyed Davoud Jazayeri,Chit Laa Poh

doi:10.3390/vaccines8030417

Abstract

Vaccination remains the major approach to the prevention of dengue. Since the only licensed live attenuated vaccine (LAV) lacked efficacy against all four serotypes, other vaccine platforms, such as synthetic peptide vaccines, should be explored. In this study, four multi-epitope peptides (P1–P4) were designed by linking a universal T-helper epitope (PADRE or TpD) to the highly conserved CD8 T cell epitope and B cell epitope (B1 or B2) against all four DENV serotypes. The multi-epitope peptides were conjugated to polystyrene nanoparticles (PSNPs) and four nanovaccines (NP1–NP4) were constructed. Mice immunized with NP1–NP4 elicited significantly higher titers of IgG and neutralizing antibodies when compared to immunization with naked P1–P4. The immune responses in mice immunized with peptide vaccines were compared with nanovaccines using ELISA, ELISPOT, and a neutralization test based on FRNT50. Among the four conjugated peptide nanovaccines, NP3 comprising the TpD T-helper epitope linked to the highly conserved B1 epitope derived from the E protein was able to elicit significant levels of IFN-γ and neutralizing antibodies to all four dengue serotypes. NP3 is a promising tetravalent synthetic peptide vaccine, but the selection of a more effective CD8+ T cell epitope and adjuvants to further improve the immunogenicity is warranted.

Highlights

Dengue virus is a mosquito-borne flavivirus with four serotypes (DENV 1–4) and is responsible for putting approximately one-third of the world’s population at risk of dengue infection
To improve the immunogenicity of these four peptide constructs, we evaluated the conjugation of the peptides to carboxylated polystyrene nanoparticles (PSNPs) using covalent conjugations and compared the magnitudes of the immune responses elicited by their corresponding peptides
The carboxylated PSNPs used in this study demonstrated efficacy as a nanoadjuvant which could increase the immunogenicity of synthetic peptides, without the need for conventional toxic adjuvants

Summary

Introduction

Dengue virus is a mosquito-borne flavivirus with four serotypes (DENV 1–4) and is responsible for putting approximately one-third of the world’s population at risk of dengue infection. There are 390 million infections annually, 96% of which are symptomatic. Severe dengue infections can lead to dengue hemorrhagic fever (DHF) or dengue shock syndrome (DSS), which is potentially deadly due to plasma leakage, severe bleeding, and organ impairment [1]. DENV is currently endemic in more than 100 countries worldwide and Southeast Asia is one of the most seriously affected regions. In Malaysia, a total of 127,407 DENV cases and 176 deaths were reported in 2019. Infection with any of the four DENV serotypes confers long-term immunity against the primary (1◦ ) infecting serotype, but only provides transient cross-protection against the remaining DENV serotypes. Severe dengue is more often associated with sequential heterotypic dengue infections

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Discussion

Conclusion