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 (S461-493) 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-NH2 via glutaraldehyde-mediated coupling to obtain the AuNP-S461-493 candidate, which showed in s.c.-immunized mice a superior immunogenicity (IgG responses) when compared to soluble S461-493; and led to increased expression of relevant cytokines in splenocyte cultures. Interestingly, the response triggered by AuNP-S461-493 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.

What Does Plant-Based Vaccine Technology Offer to the Fight against COVID-19?

The emergence of new pathogenic viral strains is a constant threat to global health, with the new coronavirus strain COVID-19 as the latest example. COVID-19, caused by the SARS-CoV-2 virus has quickly spread around the globe. This pandemic demands rapid development of drugs and vaccines. Plant-based vaccines are a technology with proven viability, which have led to promising results for candidates evaluated at the clinical level, meaning this technology could contribute towards the fight against COVID-19. Herein, a perspective in how plant-based vaccines can be developed against COVID-19 is presented. Injectable vaccines could be generated by using transient expression systems, which offer the highest protein yields and are already adopted at the industrial level to produce VLPs-vaccines and other biopharmaceuticals under GMPC-processes. Stably-transformed plants are another option, but this approach requires more time for the development of antigen-producing lines. Nonetheless, this approach offers the possibility of developing oral vaccines in which the plant cell could act as the antigen delivery agent. Therefore, this is the most attractive approach in terms of cost, easy delivery, and mucosal immunity induction. The development of multiepitope, rationally-designed vaccines is also discussed regarding the experience gained in expression of chimeric immunogenic proteins in plant systems.

Using carrot cells as biofactories and oral delivery vehicles of LTB-Syn: A low-cost vaccine candidate against synucleinopathies.

Synucleinopathies are conditions that remain with no available effective treatments thus far. Immunotherapy is a possible path to fight against such pathologies by inducing antibodies against alpha-synuclein (α-Syn), which could induce the clearance of its pathologic form. Looking to develop a new low-cost, effective vaccine against synucleinopathies; we have designed a chimeric plant-made antigen comprising the subunit B of the enterotoxin from enterotoxigenic E. coli and three B cell epitopes from α-Syn, which is named LTB-Syn. In the present study, LTB-Syn was produced in carrot cell lines as appropriate platform for the formulation of oral vaccines not requiring purification. The development of transgenic carrot cell lines took 8 months and the LTB-Syn yield reached 2.3 µg/g dry biomass. The antigen encapsulated in lyophilized carrot cells was highly stable at room temperature over a six-month period and upon heating at 50 °C for 2 h. Moreover, LTB-Syn was able to prime immune responses that, in combination with parenteral boosting using an OVA-Syn conjugate, induced significant humoral resposes in mice. Thus the carrot-made oral LTB-Syn vaccine is a promising candidate that deserves further analyses to advance in its preclinical evaluation.

LTB-Syn: a recombinant immunogen for the development of plant-made vaccines against synucleinopathies.

MAIN CONCLUSION: A recombinant antigen targeting α-synuclein was produced in the plant cell rendering an immunogenic protein capable to induce humoral responses in mice upon oral administration. Synucleinopathies are neurodegenerative diseases characterized by the abnormal accumulation of α-synuclein (α-Syn, a 140 amino acid protein that normally plays various neurophysiologic roles) aggregates. Parkinson's disease (PD) is the synucleinopathy with the highest epidemiologic impact and although its etiology remains unknown, α-Syn aggregation during disease progression pointed out α-Syn as target in the development of immunotherapies. Herein a chimeric protein, comprising the B subunit of the enterotoxin from enterotoxigenic Escherichia coli and α-Syn epitopes, was expressed in the plant cell having the potential to induce humoral responses following oral immunization. This approach will serve as the basis for the development of oral plant-based vaccines against PD with several potential advantages such as low cost, easy scale-up during production, and easy administration.