4Aii), and protected animals from your ECD+Advax-CpG55

4Aii), and protected animals from your ECD+Advax-CpG55.2 and ECD+Alum-CpG55.2 groups (total histopathology score<10) (Fig. hamsters immunized with the adjuvanted spike ECD exhibited reduced viral weight in day 13 oropharyngeal swabs and day 3 nasal turbinate tissue and experienced no recoverable infectious computer virus in day 3 lung tissue. The reduction in lung viral weight correlated with less weight loss and lower lung pathology scores. The formulations of spike ECD with Alum-CpG55.2 or Advax-CpG55.2 were protective even after just a single dose, even though 2-dose regimen performed better overall and required only half the total amount of antigen. Pre-challenge serum neutralizing antibody levels showed a strong correlation with lung protection, with a weaker correlation seen with nasal or oropharyngeal protection. This suggests that serum neutralizing antibody levels may correlate more closely with systemic, rather than mucosal, protection. The spike protein ECD with Advax-CpG55.2 formulation (Covax-19 vaccine) was selected for human clinical development. Keywords:COVID-19, SARS-Cov-2, Vaccine, Adjuvant, Advax, Pandemic, Coronavirus == 1. Introduction == Almost two years from the initial outbreak, the COVID-19 pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARSCoV2) remains a global public health crisis. As at 1 April 2022, SARS-CoV-2 had infected over 470 million people globally, with many countries now entering a fourth or even fifth disease wave[1]. Vaccines are a important tool to control the spread and impact of SARS-CoV-2, with various candidates having received emergency use authorization[2]. However, these COVID-19 vaccines are not without technical limitations with new technologies, such as mRNA-based platforms, being highly heat sensitive[3]with rigid chilly storage requirements[4]. Developing regions, e.g. Africa, continue to have limited access HUP2 to COVID-19 vaccines[5],[6]and lack the required extreme cold storage infrastructure required for mRNA vaccines. In addition, the adenovirus vector and mRNA vaccines have been associated with adverse reactions including anaphylaxis[7], central venous thrombosis[8]and myocarditis[9],[10]. This highlights the need for any diversity of vaccine platforms to tackle this still-evolving global crisis. Recombinant protein subunit vaccines have been highly Demethoxydeacetoxypseudolaric acid B analog successful against many viral and non-viral diseases[11]. A potential limitation of protein-based vaccines is usually their low immunogenicity, necessitating an adjuvant to enhance their immunogenicity[12]. Traditional aluminium hydroxide (Alum) and oil emulsion adjuvants remain prominent in COVID-19 vaccines in development[13]. Advax-CpG55.2 is a proprietary adjuvant formulation which combines Advax, a non-reactogenic adjuvant Demethoxydeacetoxypseudolaric acid B analog based on delta inulin, with a human toll-like receptor 9 (TLR-9) agonist oligonucleotide (CpG55.2) that was developed using artificial intelligence[14],[15]. Advax-CpG55.2 adjuvant has been tested in many preclinical studies[16],[17],[18],[19]and also in human clinical trials, including in vaccines against Influenza [NCT03945825;NCT03038776] and Hepatitis B [NCT01951677], where it enhanced vaccine immunogenicity while maintaining a positive safety profile. Advax-CpG adjuvant was previously shown to enhance coronavirus vaccine protection in models of severe acute respiratory syndrome (SARS)[20]and Middle East respiratory syndrome (MERS)[21]. Previously, we reported on a vaccine based on SARS-CoV-2 spike protein ECD formulated with Advax-CpG55.2 adjuvant which provided protection in ferrets[22]. In the current study, we describe the results from our screening of a range of vaccine formulations, comparing; 1. ECD versus full length (FL) spike protein both manufactured in insect cells, 2. Advax-CpG55.2 versus Demethoxydeacetoxypseudolaric acid B analog alum-CpG55.2 adjuvant, and 3. a single versus 2-dose regimen. These vaccine formulations were first evaluated in mice for immunogenicity, with protection then confirmed in hamsters. The hamster model has a quantity of advantages as SARS-CoV-2 replicates more efficiently in the lungs of hamsters and they display clinical indicators of disease, i.e. excess weight loss and lung pathology, that can Demethoxydeacetoxypseudolaric acid B analog be quantified to assess vaccine efficacy and potency[23],[24]. == 2. Methods == == 2.1. Vaccines and adjuvants == The FL vaccine antigen corresponded to the full-length of the SARS-CoV-2 spike of the original Wuhan-Hu-1 strain (accession number: NC 045512), whilst the ECD construct corresponded to aa 14-1213 of the Wuhan-Hu-1 spike protein sequence with the furin cleavage site deleted (seeFig. 1A). The constructs were produced using a Bac-to-Bac baculovirus expression system as previously explained[22]. The size and purity of the recombinant FL and ECD spike proteins were confirmed by SDS-PAGE gels. Endotoxin was measured using a PyroGene Endotoxin Detection System (Cat. No. 50-658U, LONZA, Walkersville, MD, USA) and residual.