Exosome based multivalent vaccine: achieving potent immunization, broadened reactivity, and strong T cell responses with nanograms of proteins

Abstract

Exosome based vaccines represent an interesting opportunity in the pandemic time we live. Compared to the available vaccines, an exosome-based vaccine may answer to the need of efficacy and increased safety. Here, we used exosomes to deliver a "cocktail" protein-based vaccine, in which two independent viral proteins are delivered using the exosome membrane as carrier. Cells were engineered to express either SARS-CoV-2 Delta spike (StealthTM X-Spike, STX-S) or nucleocapsid (StealthTM X-Nucleocapsid, STX-N) protein on the surface and facilitate their trafficking to the exosomes. When administered as single product, both STX-S and STX-N induced a strong immunization with the production of a potent humoral and cellular immune response. Interestingly, these effects are obtained with administration of nanograms of protein and without adjuvant. Therefore, we developed a multivalent low dose vaccine, namely STX-S+N, using a teeter-toother dose approach of STX-S and STX-N. In two independent animal models (mouse and rabbit), administration of STX-S+N resulted in increased antibody production, potent neutralizing antibodies with cross-reactivity to other VOC and strong T-cell response. Importantly, no competition in immune response was observed. Our data show that our exosome platform has an enormous potential to revolutionize vaccinology by rapidly facilitating antigen presentation, and for therapeutics by enabling cell and tissue specific targeting.

Antigen-display exosomes provide adjuvant-free protection against SARS-CoV-2 disease at nanogram levels of spike protein

“…However, the percentage of exosomes that displayed these morphologically recognizable spikes was a small minority of the exosomes, no more than 10% of the total exosome population. Thus, while these Spike/delta-CSM-2P-ΔC-ERES-containing exosomes are immunogenic( 37 ), they are by no means reflective of optimized exosome engineering.…”

The Key to Increase Immunogenicity of Next-Generation COVID-19 Vaccines Lies in the Inclusion of the SARS-CoV-2 Nucleocapsid Protein

“…Moreover, formulation of spike + nucleocapsid with cationic or anionic lipids showed that this combination of antigens induced IgG and IgA antibodies and production of IL-5 and IFN-γ [86]. Biotechnological approaches have also been employed, such as the generation of exosomes decorated with spikes (STX-S) or nucleocapsids (STX-N) [90]. These approaches led to improved immune responses, particularly with the combination of S + N. Another strategy in development involves fusing the most immunogenic regions of different SARS-CoV-2 proteins, resulting in a protein fusion called "SpiN" [91].…”