ABSTRACT
SCOPE: The purpose of this study was to look into the antiviral activity of a plant extract derived from the roots of the Saussurea lappa as a food supplement against SARS-CoV-2 infection. METHODS AND RESULTS: Vero E6 cells are employed in the study to test the neutralizing effect of Saussurea lappa extract against the SARS-CoV-2 virus. For anti-viral activity detection, a sensitive real-time cell analyzer (xCELLigence RTCA) with a high repetition rate is used. A challenge experiment in mice is planned as a result of the in vitro analysis. A challenge test against SARS-CoV-2 is performed with 10 adult female K18-hACE2 transgenic mice in each group for this purpose. The mice in the S. lappa Group are gavaged 2 days before the virus is administered intranasally (i.n.). The control group received PBS instead of the extract. SARS-CoV-2 virus is administered i.n. under anesthesia for the first 3 days of the experiment, and S. lappa extract was administered by gavage in the afternoon. On the 10th day, mice in the S. lappa group survived the study, whereas animals in the control group grew ill and/or died. In this study, the extract protects the mice against the SARS-CoV-2 virus in 90% of the cases. CONCLUSIONS: This study demonstrates that the Saussurea plant has antiviral effects against SARS-CoV-2 in vitro and in animal models.
ABSTRACT
Recombinant protein-based SARS-CoV-2 vaccines are needed to fill the vaccine equity gap. Because protein-subunit based vaccines are easier and cheaper to produce and do not require special storage/transportation conditions, they are suitable for low-/middle-income countries. Here, we report our vaccine development studies with the receptor binding domain of the SARS-CoV-2 Delta Plus strain (RBD-DP) which caused increased hospitalizations compared to other variants. First, we expressed RBD-DP in the Pichia pastoris yeast system and upscaled it to a 5-L fermenter for production. After three-step purification, we obtained RBD-DP with > 95% purity from a protein yield of > 1 g/L of supernatant. Several biophysical and biochemical characterizations were performed to confirm its identity, stability, and functionality. Then, it was formulated in different contents with Alum and CpG for mice immunization. After three doses of immunization, IgG titers from sera reached to > 106 and most importantly it showed high T-cell responses which are required for an effective vaccine to prevent severe COVID-19 disease. A live neutralization test was performed with both the Wuhan strain (B.1.1.7) and Delta strain (B.1.617.2) and it showed high neutralization antibody content for both strains. A challenge study with SARS-CoV-2 infected K18-hACE2 transgenic mice showed good immunoprotective activity with no viruses in the lungs and no lung inflammation for all immunized mice.