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

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.

Utilizing the sublingual form of squalene in COVID-19 patients: a randomized clinical trial

“…Moreover, this formulation was able to stimulate neutralizing antibodies in hamsters. Results confirmed that SQ base emulsion was safe, as demonstrated by the histopathological analysis in lungs, liver, and kidney 35 . Due to the effective properties of SQ, Solomadin et al, applied SQ in NARUVAX-C19 vaccine as an emulsion adjuvant and obtained robust broadly neutralizing humoral and T cell IFN-γ responses 36 .…”

Stability of shark (Centrophorus sp.) liver oil rich in squalene as an immunostimulant

“…Compound known to have effects on immune system as immunostimulants is squalene [6]. Squalene is known for its anticancer properties [7], cardiovascular benefits [8], and its role as a COVID-19 vaccine adjuvant [6]. The demand for squalene in the pharmaceutical industry is projected to reach 184 million USD by 2025 (9).…”

Immunogenicity and safety of adjuvant-associated COVID-19 vaccines: A systematic review and meta-analysis of randomized controlled trials

“…Despite the effectiveness of current vaccines, the constant evolution of the virus poses a significant threat to public health [ 4 , 5 ]. Adjuvants have been identified as a promising strategy to improve vaccine efficacy by promoting, improving, and maintaining the immune response to the vaccine antigen [ [6] , [7] , [8] , [9] ]. Previous experiences with influenza and malaria vaccines have demonstrated the importance of adjuvants during pandemics and their potential to accelerate vaccine development [ 10 , 11 ].…”