Synthesis and immunogenicity assessment of a gold nanoparticle conjugate for the delivery of a peptide from SARS-CoV-2

The development of vaccines is a crucial response against the COVID-19 pandemic and innovative nanovaccines could increase the potential to address this remarkable challenge. In the present study a B cell epitope (S(461-493)) from the spike protein of SARS-CoV-2 was selected and its immunogenicity validated in sheep. This synthetic peptide was coupled to gold nanoparticles (AuNP) functionalized with SH-PEG-NH(2) via glutaraldehyde-mediated coupling to obtain the AuNP-S(461-493) candidate, which showed in s.c.-immunized mice a superior immunogenicity (IgG responses) when compared to soluble S(461-493); and led to increased expression of relevant cytokines in splenocyte cultures. Interestingly, the response triggered by AuNP-S(461-493) was similar in magnitude to that induced using a conventional strong adjuvant (Freund's adjuvant). This study provides a platform for the development of AuNP-based nanovaccines targeting specific SARS-CoV-2 epitopes.