Development of Bacteriophage Virus-Like Particle Vaccines Displaying Conserved Epitopes of Dengue Virus Non-Structural Protein 1

Abstract

Dengue virus (DENV) is a major global health problem, with over half of the world’s population at risk of infection. Despite over 60 years of efforts, no licensed vaccine suitable for population-based immunization against DENV is available. Here, we describe efforts to engineer epitope-based vaccines against DENV non-structural protein 1 (NS1). NS1 is present in DENV-infected cells as well as secreted into the blood of infected individuals. NS1 causes disruption of endothelial cell barriers, resulting in plasma leakage and hemorrhage. Immunizing against NS1 could elicit antibodies that block NS1 function and also target NS1-infected cells for antibody-dependent cell cytotoxicity. We identified highly conserved regions of NS1 from all four DENV serotypes. We generated synthetic peptides to these regions and chemically conjugated them to bacteriophage Qβ virus-like particles (VLPs). Mice were immunized two times with the candidate vaccines and sera were tested for the presence of antibodies that bound to the cognate peptide, recombinant NS1 from all four DENV serotypes, and DENV-2-infected cells. We found that two of the candidate vaccines elicited antibodies that bound to recombinant NS1, and one candidate vaccine elicited antibodies that bound to DENV-infected cells. These results show that an epitope-specific vaccine against conserved regions of NS1 could be a promising approach for DENV vaccines or therapeutics to bind circulating NS1 protein.

Immunogenicity and Protective Capacity of a Virus-like Particle Vaccine against Chlamydia trachomatis Type 3 Secretion System Tip Protein, CT584

“…Antibody titers to Qβ-CT584, the mixed epitope formulation with 50% of the dosage of each VLP compared to the single epitope vaccines, were similarly high as the single epitope formulations. These results underscore the value of Qβ as a highly immunogenic VLP platform, consistent with previous research [33]. They also demonstrate that CT584 epitopes, which are not immunogenic during natural infection, have the potential to be highly immunogenic when incorporated into a VLP vaccine.…”

“…Each VLP vaccine consisted of bacteriophage Qβ capsid chemically crosslinked to peptides predicted to be B cell epitopes for C. trachomatis antigen CT584. Qβ VLPs were produced in Escherichia coli, as previously described [33]. Recombinant Qβ capsid protein self-assembles into an icosahedral capsid with t = 3 symmetry consisting of 90 protein dimers with surface exposed lysine residues.…”

“…To investigate the antibody response to CT584 epitopes when incorporated into VLP vaccines, female C57Bl/6 mice were immunized intramuscularly with either the single epitope vaccines Qβ-70 or Qβ-154, or the mixed formulation Qβ-CT584, or the unconjugated negative control Qβ three times at three-week intervals. This follows an immunization scheme previously developed for other Qβ VLP vaccines [33]. The titer of serum IgG specific to CT584 peptides 70-77 and 154-164 was measured by ELISA after immunization and prior to C. trachomatis challenge (Figure 3A).…”

Biological Nanoparticles in Vaccine Development

“…As VLPs directly mimic native viruses, these nanoparticle systems can induce strong, T-independent stimulation of B cells through BCR crosslinking ( Bachmann et al, 1993 ; Fries et al, 2021 ). VLPs also contain viral PAMPs, such as nucleic acids, that help activate, in many cases, and an adjuvant-free protective immune response ( Venter et al, 2011 ; Li M. et al, 2021 ; Ortega-Rivera et al, 2021 ; Royal et al, 2021 ; Warner and Frietze, 2021 ). Additionally, if they are made in bacteria, VLPs may contain some bacterial components that further promote a protective response without use of classical alum adjuvants ( Mohsen et al, 2021 , 2022 ).…”

“…When tested in a mouse model, immunized mice were not protected from Zika challenge, but serum antibodies from immunized mice neutralized the virus in vitro , indicating that this approach has potential for vaccine development. A similar strategy was also used to conjugate Qβ VLPs to CHIKV epitopes ( Basu et al, 2020 ) and Dengue virus (DENV) epitopes ( Warner and Frietze, 2021 ), as well as to conjugate CMV VLPs to recombinant SARS-CoV-2 spike protein ( Zha et al, 2021 ) and ZIKV immunogens ( Cabral-Miranda et al, 2019 ). Other linkers used for conjugation of VLP platforms to pathogenic antigens include SM(PEG) 4 (N-hydroxysuccinimide-poly (ethylene glycol) 4 -maleimide) ( Ortega-Rivera et al, 2021 ) for conjugation of Qβ to SARS-CoV-2 spike protein, and carbodiimide chemistry for conjugation of Yersenia pestis virulence factors ( Arnaboldi et al, 2016 ) to TMV VLPs.…”