A bioengineered pseudovirus nanoparticle displaying SARS-CoV 2 RBD fully protects mice from mortality and weight loss caused by SARS-CoV 2 challenge.

The COVID-19 pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused considerable morbidity and mortality worldwide. Although authorized COVID-19 vaccines have been shown highly effective, their significantly lower efficacy against heterologous variants, and the rapid decrease of vaccine-elicited immunity raises serious concerns, calling for improved vaccine tactics. To this end, a pseudovirus nanoparticle (PVNP) displaying the receptor binding domains (RBDs) of SARS-CoV-2 spike, named S-RBD, was generated and shown it as a promising COVID-19 vaccine candidate. The S-RBD PVNP was produced using both prokaryotic and eukaryotic systems. A 3D structural model of the S-RBD PVNPs was built based on the known structures of the S60 particle and RBDs, revealing an S60 particle-based icosahedral symmetry with multiple surface-displayed RBDs that retain authentic conformations and receptor-binding functions. The PVNP is highly immunogenic, eliciting high titers of RBD-specific IgG and neutralizing antibodies in mice. The S-RBD PVNP demonstrated exceptional protective efficacy, and fully (100%) protected K18-hACE2 mice from mortality and weight loss after a lethal SARS-CoV-2 challenge, supporting the S-RBD PVNPs as a potent COVID-19 vaccine candidate. By contrast, a PVNP displaying the N-terminal domain (NTD) of SARS-CoV-2 spike exhibited only 50% protective efficacy. Since the RBD antigens of our PVNP vaccine are adjustable as needed to address the emergence of future variants, and various S-RBD PVNPs can be combined as a cocktail vaccine for broad efficacy, these non-replicating PVNPs offer a flexible platform for a safe, effective COVID-19 vaccine with minimal manufacturing cost and time.

The influence of SARS-CoV-2 infection on expression of drug-metabolizing enzymes and transporters in a hACE2 murine model.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and the resulting Coronavirus disease 2019 emerged in late 2019 and is responsible for significant morbidity and mortality worldwide. A hallmark of severe COVID-19 is exaggerated systemic inflammation, regarded as a "cytokine storm," which contributes to the damage of various organs, primarily the lungs. The inflammation associated with some viral illnesses is known to alter the expression of drug-metabolizing enzymes and transporters. These alterations can lead to modifications in drug exposure and the processing of various endogenous compounds. Here, we provide evidence to support changes in the mitochondrial ribonucleic acid expression of a subset of drug transporters (84 transporters) in the liver, kidneys, and lungs and metabolizing enzymes (84 enzymes) in the liver in a humanized angiotensin-converting enzyme 2 receptor mouse model. Specifically, three drug transporters (Abca3, Slc7a8, Tap1) and the pro-inflammatory cytokine IL-6 were upregulated in the lungs of SARS-CoV-2 infected mice. We also found significant downregulation of drug transporters responsible for the movement of xenobiotics in the liver and kidney. Additionally, expression of cytochrome P-450 2f2 which is known to metabolize some pulmonary toxicants, was significantly decreased in the liver of infected mice. The significance of these findings requires further exploration. Our results suggest that further research should emphasize altered drug disposition when investigating therapeutic compounds, whether re-purposed or new chemical entities, in other animal models and ultimately in individuals infected with SARS-CoV-2. Moreover, the influence and impact of these changes on the processing of endogenous compounds also require further investigation.

A hepatitis B virus core antigen-based virus-like particle vaccine expressing SARS-CoV-2 B and T cell epitopes induces epitope-specific humoral and cell-mediated immune responses but confers limited protection against SARS-CoV-2 infection.

The hepatitis B virus core antigen (HBcAg) tolerates insertion of foreign epitopes and maintains its ability to self-assemble into virus-like particles (VLPs). We constructed a ∆HBcAg-based VLP vaccine expressing three predicted severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) B and T cell epitopes and determined its immunogenicity and protective efficacy. The recombinant ∆HBcAg-SARS-CoV-2 protein was expressed in Escherichia coli, purified, and shown to form VLPs. K18-hACE2 transgenic C57BL/6 mice were immunized intramuscularly with ∆HBcAg VLP control (n = 15) or ∆HBcAg-SARS-CoV-2 VLP vaccine (n = 15). One week after the 2nd booster and before virus challenge, five ∆HBcAg-SARS-CoV-2 vaccinated mice were euthanized to evaluate epitope-specific immune responses. There is a statistically significant increase in epitope-specific Immunoglobulin G (IgG) response, and statistically higher interleukin 6 (IL-6) and monocyte chemoattractant protein-1 (MCP-1) expression levels in ∆HBcAg-SARS-CoV-2 VLP-vaccinated mice compared to ∆HBcAg VLP controls. While not statistically significant, the ∆HBcAg-SARS-CoV-2 VLP mice had numerically more memory CD8+ T-cells, and 3/5 mice also had numerically higher levels of interferon gamma (IFN-γ) and tumor necrosis factor (TNF). After challenge with SARS-CoV-2, ∆HBcAg-SARS-CoV-2 immunized mice had numerically lower viral RNA loads in the lung, and slightly higher survival, but the differences are not statistically significant. These results indicate that the ∆HBcAg-SARS-CoV-2 VLP vaccine elicits epitope-specific humoral and cell-mediated immune responses but they were insufficient against SARS-CoV-2 infection.

A Novel Bacterial Protease Inhibitor Adjuvant in RBD-Based COVID-19 Vaccine Formulations Containing Alum Increases Neutralizing Antibodies, Specific Germinal Center B Cells and Confers Protection Against SARS-CoV-2 Infection in Mice.

In this work, we evaluated recombinant receptor binding domain (RBD)-based vaccine formulation prototypes with potential for further clinical development. We assessed different formulations containing RBD plus alum, AddaS03, AddaVax, or the combination of alum and U-Omp19: a novel Brucella spp. protease inhibitor vaccine adjuvant. Results show that the vaccine formulation composed of U-Omp19 and alum as adjuvants has a better performance: it significantly increased mucosal and systemic neutralizing antibodies in comparison to antigen plus alum, AddaVax, or AddaS03. Antibodies induced with the formulation containing U-Omp19 and alum not only increased their neutralization capacity against the ancestral virus but also cross-neutralized alpha, lambda, and gamma variants with similar potency. Furthermore, the addition of U-Omp19 to alum vaccine formulation increased the frequency of RBD-specific geminal center B cells and plasmablasts. Additionally, U-Omp19+alum formulation induced RBD-specific Th1 and CD8+ T-cell responses in spleens and lungs. Finally, this vaccine formulation conferred protection against an intranasal severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) challenge of K18-hACE2 mice.