SARS-CoV-2 subunit vaccine adjuvants and their signaling pathways

Abstract

Introduction: Vaccines are the agreed upon weapon against the COVID-19 pandemic. This review discusses about COVID-19 subunit vaccines adjuvants and their signaling pathways, which could provide a glimpse into the selection of appropriate adjuvants for prospective vaccine development studies. Areas covered: In the introduction, a brief background about the SARS-CoV-2 pandemic, the vaccine development race and classes of vaccine adjuvants were provided. . The antigen, trial stage, and types of adjuvants were extracted from the included articles and thun assimilated. Finally, the pattern recognition receptors (PRRs), their classes, cognate adjuvants, and potential signaling pathways were comprehended. Expert opinion: Adjuvants are unsung heroes of subunit vaccines. The in silico studies are very vital in avoiding several costly trial errors and save much work times. The majority of the (pre)clinical studies are promising. It is encouraging that most of the selected adjuvants are novel. Much emphasis must be paid to the optimal paring of antigen-adjuvant-PRRs for obtaining the desired vaccine effect. A good subunit vaccine/adjuvant is one that has high efficacy, safety, dose sparing, and rapid seroconversion rate and broad spectrum of immune response. In the years to come, COVID-19 adjuvanted subunit vaccines are expected to have superior utility than any other vaccines for various reasons.

Saponins: Research Progress and Their Potential Role in the Post-COVID-19 Pandemic Era

“…As a result, there is currently a therapeutic need to improve the efficacy and safety of vaccines against COVID-19. This has, in turn, reinforced the importance of innovation and the use of better immunostimulants for the production of vaccines that provide better, safe, and long-term immunological protection [ 49 , 116 , 117 , 120 ]. In this context, it has been demonstrated that the protective immunity of certain types of vaccines could be enhanced by the addition or substitution of different adjuvants [ 120 , 121 ].…”

Comparative Immunogenicity of the Recombinant Receptor-Binding Domain of Protein S SARS-CoV-2 Obtained in Prokaryotic and Mammalian Expression Systems

“…One of the major drawbacks of subunit vaccines is a lower immunogenicity compared with attenuated vaccines. To enhance the potency of subunit vaccines, use of specific adjuvants and multiple injections are needed [8,9]. Another potential disadvantage of subunit vaccines is their relatively high manufacturing cost, especially if the mammalian expression system is used.…”

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“…In addition to finding new adjuvants, researchers are also modifying existing adjuvants to increase immune-inducing ability and reduce toxicity. It is known that their modification of the epitope further enhances the immunogenicity of subunit vaccines, increasing stability, halflife, and solubility which collectively increase the Th1 response (Mekonnen et al, 2022).…”