Journal: bioRxiv

Article Title: An enveloped virus-like particle vaccine expressing a stabilized prefusion form of the SARS-CoV-2 spike protein elicits potent immunity after a single dose

doi: 10.1101/2021.04.28.441832

Figure Lengend Snippet: (a) Schematic representation of the challenge experiments. Each challenge experiment used 2 groups of 15 Syrian gold hamsters. In regimen II, animals received 2 IM injections of VBI-2902a (2µg of S per dose) or placebo saline buffer administered at 3 weeks interval. In regimen I, animals received a single injection of VBI-2902a or Saline buffer. Blood was collected 2 weeks after each injection. Three weeks after the last injection corresponding to day 42 in regimen II and day 21 in regimen I, hamsters were exposed to SARS-CoV-2 at 1×10 5 TCID50 per animal via both nares. At 3 days post infection (dpi), 6 animals per groups were sacrificed for viral load analysis. The remaining animals were clinically evaluated daily until end of study at 14dpi. (b) Anti-SARS-CoV-2 S(S1+S2) total IgG EPT measured by ELISA 2 weeks after each immunization. (c) Neutralization activity was measured by PRNT90 in immunized groups; results are represented as PRNT90 EPT.

Article Snippet: Determination of Ab binding titers to the RBD was performed using SARS-COV-2 RDB recombinant protein (Sinobiological).

Techniques: Injection, Infection, Enzyme-linked Immunosorbent Assay, Neutralization, Activity Assay

Journal: bioRxiv

Article Title: An enveloped virus-like particle vaccine expressing a stabilized prefusion form of the SARS-CoV-2 spike protein elicits potent immunity after a single dose

doi: 10.1101/2021.04.28.441832

Figure Lengend Snippet: (a) Schematic representation of SARS-COV-2 S plasmid constructs. TM-CTD: Transmembrane cytoplasmic terminal domain. (b) Expression of SARS-CoV-2 S analyzed by Western-blot of SARS-CoV-2 eVLPs and recombinant proteins using a rabbit polyclonal Ab (pAb, upper panel) raised against SARS-CoV-2 RBD (Sinobiological) or COVID-19 convalescent human serum (HuCS, bottom panel). eVLPs produced with Gag plasmid only (Gag eVLPs) and recombinant SARS-CoV-2 S proteins were used as negative and positive controls respectively. r-S: recombinant native S, r-SP: recombinant prefusion S protein containing a mutated furin cleavage domain (RRAR → GSAS), replacement of 2 proline (KV → PP) and a trimerization domain.

Article Snippet: Determination of Ab binding titers to the RBD was performed using SARS-COV-2 RDB recombinant protein (Sinobiological).

Techniques: Plasmid Preparation, Construct, Expressing, Western Blot, Recombinant, Produced

Journal: bioRxiv

Article Title: An enveloped virus-like particle vaccine expressing a stabilized prefusion form of the SARS-CoV-2 spike protein elicits potent immunity after a single dose

doi: 10.1101/2021.04.28.441832

Figure Lengend Snippet: (a) Ab binding titers against SARS-CoV-2 S (S1+S2). Plasma samples were grouped according to initial screening by YHLO method in two groups Low and High Ab titers prior to be tested in the in-house ELISA against a recombinant S(S1+S2). (b) Neutralizing activity was measured by PRNT90 as described in Material and Methods. Results are represented as end point titers (EPT).

Article Snippet: Determination of Ab binding titers to the RBD was performed using SARS-COV-2 RDB recombinant protein (Sinobiological).

Techniques: Binding Assay, Enzyme-linked Immunosorbent Assay, Recombinant, Activity Assay

Journal: bioRxiv

Article Title: An enveloped virus-like particle vaccine expressing a stabilized prefusion form of the SARS-CoV-2 spike protein elicits potent immunity after a single dose

doi: 10.1101/2021.04.28.441832

Figure Lengend Snippet: Four groups of 10 C57BL/6 mice received 2 injections of various forms of SARS-CoV-2 S eVLPs or recombinant SP at day 0 and 21 a indicated on legend, S: native S, SG: S with VSV-G tail, SP: prefusion S, SPG: prefusion S with VSV-G tail, r-SP: recombinant SP protein. Sera were collected 2 weeks after each injection. (a) Pooled sera from each group were analyzed for specific SARS-CoV-2 S(S1+S2) total IgG; results are represented as EPT corresponding to the first dilution that gave an OD 3-fold above background. (b) Pooled sera from each group were analyzed in PRNT assay with a 90% threshold (PRNT90) as described in Material and Methods. A pool of human sera from COVID-19 convalescent patients with moderate disease (HuCS) was used as reference. (c-d) Individual sera were analyzed in ELISA using recombinant SARS-CoV-2 S(S1+S2) protein (c) or recombinant SARS-CoV-2 RBD protein (d). P values from Kruskall-Wallis test comparing groups are indicated in c and d.

Article Snippet: Determination of Ab binding titers to the RBD was performed using SARS-COV-2 RDB recombinant protein (Sinobiological).

Techniques: Recombinant, Injection, Plaque Reduction Neutralization Test, Enzyme-linked Immunosorbent Assay

Journal: bioRxiv

Article Title: An enveloped virus-like particle vaccine expressing a stabilized prefusion form of the SARS-CoV-2 spike protein elicits potent immunity after a single dose

doi: 10.1101/2021.04.28.441832

Figure Lengend Snippet: At day 0 and 21, five groups of 10 C57BL/6 mice received 2 injections of S eVLPs in the presence of various adjuvants as indicated in legends and described in Material and Methods. Sera and splenocytes were collected 2 weeks after the second injection. (a) Numbers of IFNγ producing cells per million splenocytes collected 2 weeks after the second injection were measured by ELISpot using peptide pool covering the entire S(S1+S2) protein. (b) Total IgG were measured in ELISA against recombinant SARS-CoV-2 S(S1+S2) protein, results are represented as EPT. (c-d) Isotype usage was determined in individual sera by specific ELISA using HRP conjugate goat Ab against mouse IgG1 and IgG2. (c) Results are expressed as the ratio of IgG2b to IgG1. Results from Kruskall-Wallis comparison of groups are indicated.

Article Snippet: Determination of Ab binding titers to the RBD was performed using SARS-COV-2 RDB recombinant protein (Sinobiological).

Techniques: Injection, Enzyme-linked Immunospot, Enzyme-linked Immunosorbent Assay, Recombinant

Journal: bioRxiv

Article Title: An enveloped virus-like particle vaccine expressing a stabilized prefusion form of the SARS-CoV-2 spike protein elicits potent immunity after a single dose

doi: 10.1101/2021.04.28.441832

Figure Lengend Snippet: (a-d) Two groups of 10 mice were immunized twice at 3 weeks interval with VBI-2902a or VBI-2902e containing 0.2 µg of S protein. Blood was collected 2 weeks after each injection, P1d: post 1 st dose, P2d: post 2 nd dose. (a) Ab binding titer against recombinant S(S1+S2) compared to human convalescent sera, measured by ELISA, (b) neutralization end point titers measured by PRNT90, (c) Ab binding titers against recombinant S(S1+S2), recombinant RBD or recombinant S2 measured by ELISA in sera after the 2 nd dose. Results from Kruskall-Wallis comparison of groups are indicated for A and B. (d) Numbers of IFNγ producing cells per million splenocytes collected 2 weeks after each injection were measured by ELISpot using Pepmix 1 or Pepmix 2 preferentially covering SARS-CoV-2 S1 domain or tS2 domain respectively. (e) Kinetic of the humoral response after single injection of VBI-2902a calculated as end point titer determined in ELISA and PRNT90.

Article Snippet: Determination of Ab binding titers to the RBD was performed using SARS-COV-2 RDB recombinant protein (Sinobiological).

Techniques: Injection, Binding Assay, Recombinant, Enzyme-linked Immunosorbent Assay, Neutralization, Enzyme-linked Immunospot

Journal: bioRxiv

Article Title: An enveloped virus-like particle vaccine expressing a stabilized prefusion form of the SARS-CoV-2 spike protein elicits potent immunity after a single dose

doi: 10.1101/2021.04.28.441832

Figure Lengend Snippet: Hamsters from experiment described in were monitored daily for weight change. Results are represented for each animal in each groups as kinetic of weight change from SARS-CoV-2 exposure to day 9 after infection. (a) represents the weight change observed in the 2-dose regimen (II), (b) represent the weight change observed in the single dose regimen (I).

Article Snippet: Determination of Ab binding titers to the RBD was performed using SARS-COV-2 RDB recombinant protein (Sinobiological).

Techniques: Infection

Journal: bioRxiv

Article Title: An enveloped virus-like particle vaccine expressing a stabilized prefusion form of the SARS-CoV-2 spike protein elicits potent immunity after a single dose

doi: 10.1101/2021.04.28.441832

Figure Lengend Snippet: (a-b) At 3dpi, qRT-PCR assays were performed on RNA from samples of nasal washes, lung tissues (cranial and caudal lobes) using SARS-CoV-2 specific primers. Results were expressed as copy number per gram of tissue sample. (c-d) Correlation analysis of viral loads measured in lung caudal lobe and PRNT90.

Article Snippet: Determination of Ab binding titers to the RBD was performed using SARS-COV-2 RDB recombinant protein (Sinobiological).

Techniques: Quantitative RT-PCR