Squalene in oil-based adjuvant improves the immunogenicity of SARS-CoV-2 RBD and confirms safety in animal models

PLoS One. 2022 Aug 23;17(8):e0269823. doi: 10.1371/journal.pone.0269823. eCollection 2022.

Abstract

COVID-19 pandemic has accelerated the development of vaccines against its etiologic agent, SARS-CoV-2. However, the emergence of new variants of the virus lead to the generation of new alternatives to improve the current sub-unit vaccines in development. In the present report, the immunogenicity of the Spike RBD of SARS-CoV-2 formulated with an oil-in-water emulsion and a water-in-oil emulsion with squalene was evaluated in mice and hamsters. The RBD protein was expressed in insect cells and purified by chromatography until >95% purity. The protein was shown to have the appropriate folding as determined by ELISA and flow cytometry binding assays to its receptor, as well as by its detection by hamster immune anti-S1 sera under non-reducing conditions. In immunization assays, although the cellular immune response elicited by both adjuvants were similar, the formulation based in water-in-oil emulsion and squalene generated an earlier humoral response as determined by ELISA. Similarly, this formulation was able to stimulate neutralizing antibodies in hamsters. The vaccine candidate was shown to be safe, as demonstrated by the histopathological analysis in lungs, liver and kidney. These results have shown the potential of this formulation vaccine to be evaluated in a challenge against SARS-CoV-2 and determine its ability to confer protection.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adjuvants, Immunologic
  • Animals
  • Antibodies, Neutralizing
  • Antibodies, Viral
  • COVID-19* / prevention & control
  • Cricetinae
  • Emulsions
  • Humans
  • Immunogenicity, Vaccine
  • Mice
  • Mice, Inbred BALB C
  • Models, Animal
  • Pandemics / prevention & control
  • SARS-CoV-2
  • Spike Glycoprotein, Coronavirus
  • Squalene
  • Viral Vaccines*
  • Water

Substances

  • Adjuvants, Immunologic
  • Antibodies, Neutralizing
  • Antibodies, Viral
  • Emulsions
  • Spike Glycoprotein, Coronavirus
  • Viral Vaccines
  • spike protein, SARS-CoV-2
  • Water
  • Squalene

Grants and funding

This study was funded/ supported by Laboratorios de Investigación y Desarrollo - FARVET and partially by Fondo Nacional de Desarrollo Científico, Tecnológico y de Innovación Tecnológica - FONDECYT (https://www.fondecyt.gob.pe/) under the contract 060-2020-FONDECYT. MFD and MZ were granted by Consejo Nacional de Ciencia, Tecnología e Innovación Tecnológica (CONCYTEC). These funder supported salaries for RCG, RMM, APA, DRM, KGM, AM, SQG, MCM, AAAM, IRO, MCO, EHG, NPM, GIR, YSA and DVP and supplied materials for the study. The funders had no role in study desing, data collection and analysis, decision to publish, or preparation of manuscript.