Coronavirus disease (COVID-19) causes a serious threat to human health. Virus-like particles (VLPs) constitute a promising platform in SARS-CoV-2 vaccine development. In this study, the E, M, and S genes were cloned into multiple cloning sites of a new triple expression plasmid with one p10 promoter, two pPH promoters, and three multiple cloning sites. The plasmid was transformed into DH10 Bac^TMEscherichia coli competent cells to obtain recombinant bacmid. Then the recombinant bacmid was transfected in ExpiSf9^TM insect cells to generate recombinant baculovirus. After ExpiSf9^TM cells infection with the recombinant baculovirus, the E, M, and S proteins were expressed in insect cells. Finally, SARS-CoV-2 VLPs were self-assembled in insect cells after infection. The morphology and the size of SARS-CoV-2 VLPs are similar to the native virions.

The application-based flipped classroom (APP-FC) is an innovative teaching-learning model that has not been applied and assessed in basic medical curricula teaching in China. The aim of this investigation is to assess students’ perceptions to the APP-based flipped classroom (APP-FC) teaching model in an immunology course. The data of this study were collected from second-year medical students (n = 92) at Lanzhou University. One class (n = 50), as a control group, was offered lecture-based learning (LBL), while the other class (n = 42), as the APP-FC group, was given lecture-based instruction and the APP-FC teaching model during September–November 2017. Afterward, the perceptions of students on APP-FC teaching model were evaluated using questionnaires. Students responded that APP-FC improves their motivation (83%) and interest in learning immunology (81%), as well as their self-directed learning skills (81%). Compared to the traditional lecture-based instruction, the APP-FC noticeably improved students’ motivation in learning (P = 0.011), self-directed learn skills (P = 0.001), memory abilities (P = 0.009), and problem-solving abilities (P = 0.010). Most medical students’ scores (60%) in the final examination were more than 80 points after implementing an APP-FC model as compared to the control group (40%). The majority of students (70%) preferred the APP-FC teaching approach over traditional lecture-based pedagogy. The implementation of the APP-FC teaching model could improve students’ learning motivation, self-directed learn skills, and problem-solving abilities, which is a preferable teaching model for medical immunology courses in China.

Dendritic cells (DCs) are professional antigen-presenting cells that play an important role in both innate and acquired immune responses against pathogens. However, the role of DCs in coronavirus disease 2019 (COVID-19) is unclear. Virus-like particles (VLPs) that structurally mimic the original virus are one of the candidates COVID-19 vaccines. In the present study, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) VLPs were used as an alternative to live virus to evaluate the interaction of the virus with DCs. The results revealed that SARS-CoV-2 VLPs induced DC maturation by augmenting cell surface molecule expression (CD80, CD86, and major histocompatibility complex class II (MHC-II)) and inflammatory cytokine production (tumor necrosis factor-α, interleukin (IL)-1β, IL-6, and IL-12p70) in DCsviathe mitogen-activated protein kinase and nuclear factor-κB signaling pathways. In addition, mature DCs induced by SARS-CoV-2 VLPs promoted T cell proliferation, which was dependent on VLPs concentration. Our results suggest that SARS-CoV-2 VLPs regulate the immune response by interacting with DCs. These findings will improve the understanding of SARS-CoV-2 pathogenesis and SARS-CoV-2 vaccine development.

Coronavirus disease (COVID-19) causes a serious threat to human health. To production of SARS-COV-2 virus-like particles (VLPs) in insect cells for vaccine development and scientific research. The E, M and S genes were cloned into multiple cloning sites of the new triple expression plasmid with one p10 promoter, two pPH promoters and three multiple cloning sites. The plasmid was transformed into DH10 Bac ^TM Escherichia coli competent cells to obtain recombinant bacmid. Then the recombinant bacmid was transfected in ExpiSf9™ insect cells to generate recombinant baculovirus. After ExpiSf9™ infected with the recombinant baculovirus, the E, M, and S protein co-expressed in insect cells. Finally, SARS-CoV-2 VLPs were self-assembled in insect cells after infection. The morphology and the size of SARS-CoV-2 VLPs are similar to the native virions.