A Novel Polymer Nanoparticle Polydimethyl Diallyl Ammonium Chloride as An Adjuvant Enhances the Immune Response of SARS‐CoV‐2 Subunit Vaccine

Abstract

The COVID‐19 pandemic caused by SARS‐CoV‐2 has had a significant impact on global health and the economy. It has underscored the urgent need for a stable, easily produced and effective vaccine. In this study, we presented a novel approach using SARS‐CoV‐2 spike (S) protein‐conjugated nanoparticles (NPs) in combination with cGAMP (S‐NPs‐cGAMP) as a subunit vaccine. When mice were immunized, the antiserum of S‐NPs‐cGAMP group exhibited a 16‐fold increase in neutralizing activity against a pseudovirus, compared to S protein group. Additionally, S‐NPs‐cGAMP induced even higher levels of neutralizing antibodies. Remarkably, the vaccine also triggered a robust humoral immune response, as evidenced by a notable elevation in virus‐specific IgG and IgM antibodies. Furthermore, after 42 days of immunization, there was an observed increase in specific immune cell populations in the spleen. CD3+CD4+ and CD3+CD8+T lymphocytes, as well as B220+CD19+ and CD3−CD49b+ NK lymphocytes, showed an upward trend, indicating a positive cellular immune response. Moreover, the S‐NPs‐cGAMP demonstrated promising results against the Delta strain and exhibited good cross‐neutralization potential against other variants. These findings suggest that pDMDAAC NPs is potential adjuvant and could serve as a versatile platform for future vaccine development.This article is protected by copyright. All rights reserved