Identification of four linear B-cell epitopes on the SARS-CoV-2 spike protein able to elicit neutralizing antibodies

SARS-CoV-2 unprecedentedly threatens the public health at worldwide level. There is an urgent need to develop an effective vaccine within a highly accelerated time. Here, we present the most comprehensive S-protein-based linear B-cell epitope candidate list by combining epitopes predicted by eight widely-used immune-informatics methods with the epitopes curated from literature published between Feb 6, 2020 and July 10, 2020. We find four top prioritized linear B-cell epitopes in the hotspot regions of S protein can specifically bind with serum antibodies from horse, mouse, and monkey inoculated with different SARS-CoV-2 vaccine candidates or a patient recovering from COVID-19. The four linear B-cell epitopes can induce neutralizing antibodies against both pseudo and live SARS-CoV-2 virus in immunized wild-type BALB/c mice. This study suggests that the four linear B-cell epitopes are potentially important candidates for serological assay or vaccine development.

Recombinant Fc-fusion vaccine of RBD induced protection against SARS-CoV-2 in non-human primate and mice

The severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) continues to infect people globally. The increased COVID-19 cases and no licensed vaccines highlight the need to develop safe and effective vaccines against SARS-CoV-2 infection. Multiple vaccines candidates are under pre-clinical or clinical trails with different strengths and weaknesses. Here we developed a pilot scale production of a recombinant subunit vaccine (RBD-Fc Vacc) with the Receptor Binding Domain of SARS-CoV-2 S protein fused with the Fc domain of human IgG1. RBD-Fc Vacc induced SARS-CoV-2 specific neutralizing antibodies in non-human primates and human ACE2 transgenic mice. The antibodies induced in macaca fascicularis neutralized three divergent SARS-CoV2 strains, suggesting a broader neutralizing ability. Three times immunizations protected Macaca fascicularis (20ug or 40ug per dose) and mice (10ug or 20ug per dose) from SARS-CoV-2 infection respectively. These data support clinical development of SARS-CoV-2 vaccines for humans. RBD-Fc Vacc is currently being assessed in randomized controlled phase 1/II human clinical trails. SummaryThis study confirms protective efficacy of a SARS-CoV-2 RBD-Fc subunit vaccine.

Rapid adaptation of SARS-CoV-2 in BALB/c mice: Novel mouse model for vaccine efficacy

Coronavirus disease 2019 (COVID-19) threatens global public health and economy. In order to develop safe and effective vaccines, suitable animal models must be established. Here we report the rapid adaption of SARS-CoV-2 in BALB/c mice, based on which a convenient, economical and effective animal model was developed. Specifically, we found that mouse-adapted SARS-CoV-2 at passage 6 (MACSp6) efficiently infected both aged and young wild-type BALB/c mice, resulting in moderate pneumonia as well as inflammatory responses. The elevated infectivity of MACSp6 in mice could be attributed to the substitution of a key residue (N501Y) in the receptorbinding domain (RBD). Using this novel animal model, we further evaluated the in vivo protective efficacy of an RBD-based SARS-CoV-2 subunit vaccine, which elicited highly potent neutralizing antibodies and conferred full protection against SARS-CoV-2 MACSp6 challenge. This novel mouse model is convenient and effective in evaluating the in vivo protective efficacy of SARS-CoV-2 vaccine. SummaryThis study describes a unique mouse model for SARS-CoV-2 infection and confirms protective efficacy of a SARS-CoV-2 RBD subunit vaccine.

Oncolytic Activity of a Novel Influenza A Virus Carrying Granulocyte-Macrophage Colony-Stimulating Factor in Hepatocellular Carcinoma.

Oncolytic virotherapy is a promising strategy for the treatment of cancer. Influenza A virus has shown potential as an oncolytic agent. In this study, a recombinant PR8 influenza viral vector, called delNS1-GM-CSF, was generated with a partial deletion in NS and the granulocyte-macrophage colony-stimulating factor (GM-CSF) coding sequence inserted into the influenza nonstructural protein 1 gene. The morphological characteristics of delNS1-GM-CSF were examined. The delNS1-GM-CSF virus replicated well in various cell lines, including MDCK, A549, SMCC7721, and HepG2 cells. Moreover, selective cytotoxicity of the virus was observed in various hepatocellular carcinoma (HCC) cell lines, while no effect was demonstrated in the normal liver cell line LO2, as indicated by 3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyltetrazolium bromide and crystal violet assays. Importantly, using a model based on the growth of HepG2 cells as a xenograft in nude mice, it was found that a reassortant delNS1-GM-CSF virus inhibited tumor growth significantly following intratumoral injection in a dose-dependent manner. Ex vivo results showed that the tumor inhibition efficacy of delNS1-GM-CSF was observed in HCC clinical samples. Taken together, these results are the first to demonstrate that influenza A viruses may have potential as oncolytic virotherapeutic agents against HCC.

Preparation of the Coxsackievirus A16 VP1 subunit vaccine and detection of its immunogenicity / 中华微生物学和免疫学杂志

Objective To prepare VP1 protein vaccine of Coxsackievirus A16(CA16) and evalu-ate immunngenicity the subunit vaccines of Coxsackievirus (VP1), and to establish foundation for studying CA16 vaccine. Methods CA16 VP1 was amplified by RT-PCR and cloned into pFastBac HT A plasmid, recombinated with Bacmid DNA by transposition reaction and then transfected Sf9 cell, mixed with adjuvant AI(OH)_3. After immunization BALB/c mice, evaluating immune effectiveness after booster injections 2 weeks. Results The expressed protein was analyzed by SDS-PAGE and Western blot, mice immunized with CA16 (VP1) both induced specific IgG antibody and neutralization antibody. The best immunization antigen was 20 μg, IgG antibody was 1: 1600, neutralization antibody was 1:250, typical Th1/Th2 immune response was determined by lymphocyte proliferation assay and cytokine analysis. Conclusion The CA16 VP1 gene was cloned successfully and expressed in Sf9 insect cells, CA16 VP1 protein vaccine induced both humoral and cellular immune response, to lay solid foundation for further study on CA16 vaccine.