How effective are multivalent exosome-based COVID-19 vaccines?

In a recent study posted on Bio Rxiv*Preprint server, researchers evaluated the efficacy of a multivalent exosome-based coronavirus disease 2019 (COVID-19) vaccine.

Background

Despite the clear utility of COVID-19 messenger ribonucleic acid (mRNA)-based vaccines, studies suggest that these vaccines may prove long-term, possibly due to their lack of cross-reactivity to novel variants of concern (VOCs). This has led to the need for regular booster injections to ensure long-term protection against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). rice field.

Therefore, there is an urgent need to create new COVID-19 vaccination methods.Options include the SARS-CoV-2 spike antigen (stealth^TMs X-Spike, STX-S) with more conserved SARS-CoV-2 antigens such as the SARS-CoV-2 nucleocapsid (STX-N) in a “mix and match” strategy. This strategy expands the immune response at the humoral and T-cell level, enhancing protection against current and future forms of the virus.

About research

In the current study, researchers used exosomes to develop a ‘cocktail’ protein-based vaccination containing two different viral proteins delivered via the exosomal membrane.

STX cells were generated by lentiviral transduction and surface expression of SARS-CoV-2 proteins was assessed using flow cytometry. STX exosomes were isolated from modified 293F cell culture supernatant using Capricor’s lab-scale purification method. We evaluated STX exosomes using transmission electron microscopy (TEM) imaging. In addition, an enzyme-linked immunosorbent assay (ELISA) was used to measure the concentration of SARS-CoV-2 nucleocapsid (Ncap) antigen in STX-N exosomes and SARS-CoV-2 spike antigen in STX-S exosomes. bottom.

To confirm the ability of STX-N and STX-S exosomes to generate an immune response, the team injected spikes and nucleocapsids. antigen Mice are administered with a 10ng formulation of STX-N and STX-S exosomes. To demonstrate the efficacy of exosome delivery, either Ncap or spike recombinant proteins were delivered conjugated with an adjuvant.

Next, we evaluated the immune response of the multivalent vaccine induced by combining STX-N and STX-S exosomes. Mice were administered three different doses of STX-S+N via two intramuscular (im) injections. Three weeks later, a second im injection, a boost injection, was given. Phosphate-buffered saline (PBS) was used as a negative control in this study. Evaluation of immunity by the STX-S+N vaccine was performed by quantifying antibodies generated against spike and Ncap. In addition, antigen-specific T cell responses were assessed by ELISpot to assess T cell responses to STX-S+N.

result

Compared to parental 293F cells, SARS-CoV-2 Ncap and spike expression was more than 95% higher than STX cells. The estimated average diameters of purified STX-N and STX-S exosomes were 140.4 nm and 144.6 nm, respectively. The expected polydispersity index (PDI) was less than 0.2.

Nanoparticles with a visible lipid bilayer and characteristic exosome size and shape were detected. These nanoparticles were spherical, smooth, and contained a lipid bilayer. Importantly, the presence of spike protrusions on the STX-S nanoparticles surface spike protein About exosomes. Nucleocapsids have a unique lipid bilayer that is thicker than naive exosomes, indicating accumulation of particles within the exosome membrane.

Spike protein was found in STX-S cells and exosomes, and exosome samples contained high concentrations of spike protein. Nucleocapsid levels were higher in exosomes and cells generated from STX-N. Using his bead-based CD81 test, the SARS-CoV-2 proteins Ncap and spike were identified on the exosome membrane and an expression of >75% was observed in conjunction with the exosome-specific marker CD81.

Antibody production increased after the first injection and rose consistently after booster doses. A single dose of STX-S+N increased immunoglobulin (Ig)-G levels to spike by up to 30-fold, but there was no significant difference between the three doses. After full vaccination, doses 1 and 2 increased antibodies to Spike by 1,500-fold, while dose 3 increased antibodies by 280-fold. In contrast, a dose-response relationship was reported for Ncap. Dose 1 had a 1.5-fold increase, Dose 2 had an approximately 4-fold increase, and Dose 3 had an almost 7-fold increase. His IgG against Ncap after completion of the vaccination cycle. There is no significant difference between doses.

STX-S+N vaccination produced antigen-specific and multifunctionality T cells reaction.Baseline interferon (IFN)-ƨ responses were similar between cohorts, but examination of IFN-ƨ-secreting cells ex vivo Stimulation with Spike or Ncap revealed a significant increase in STX-S+N vaccine-immunized spleens, indicating a Th1-biased CD8+ T cell response. Despite STX-S+N vaccination, he had an average 7-fold increase in IFN-Ɣ responses after spike stimulation. A dose-response trend was observed after Ncap stimulation, with a 7-fold increase in mice receiving the lowest dose of Ncap and a 3-fold increase in animals receiving either dose 2 or 3.

Overall, the results of this study demonstrate that a single dose of double-antigen vaccination is effective against a range of SARS-CoV-2 VOCs, has greater immunological potency, and is less potent than previously licensed vaccines. We have shown that it may be used to strengthen established protections. Stealth X^TMs The vaccine technology employed in this study elicited strong and broad immune responses without the need for adjuvants. The researchers believe this work, along with its multiplexing and rapid turnaround capabilities, could facilitate research into next-generation vaccines.

*Important Notices

bioRxiv publishes non-peer-reviewed, preliminary scientific reports and should not be considered conclusive, to guide clinical practice/health-related actions, or to be treated as established information .