Safety and immunogenicity of two recombinant DNA COVID-19 vaccines containing the coding regions of the spike or spike and nucleocapsid proteins: an interim analysis of two open-label, non-randomised, phase 1 trials in healthy adults.

BACKGROUND: We assessed the safety and immunogenicity of two recombinant DNA vaccines for COVID-19: GX-19 containing plasmid DNA encoding the SARS-CoV-2 spike protein, and GX-19N containing plasmid DNA encoding the SARS-CoV-2 receptor-binding domain (RBD) foldon, nucleocapsid protein, and plasmid DNA encoding the spike protein. METHODS: Two open-label non-randomised phase 1 trials, one of GX-19 and the other of GX-19N were done at two hospitals in South Korea. We enrolled healthy adults aged 19-49 years for the GX-19 trial and healthy adults aged 19-54 years for the GX-19N trial. Participants who tested positive by serological testing for SARS-CoV-2 were excluded. At 4-week intervals, the GX-19 trial participants received two vaccine doses (either 1·5 mg or 3·0 mg), and the GX-19N trial participants received two 3·0 mg doses. The vaccines were delivered intramuscularly using an electroporator. The participants were followed up for 52 weeks after first vaccination. Data collected up to day 57 after first vaccination were analysed in this interim analysis. The primary outcome was safety within 28 days after each vaccination measured in the intention-to-treat population. The secondary outcome was vaccine immunogenicity using blood samples collected on day 43 or 57 after first vaccination measured in the intention-to-treat population. The GX-19 (NCT044445389) and GX-19N (NCT04715997) trials are registered with ClinicalTrials.gov. FINDINGS: Between June 17 and July 30, 2020, we screened 97 individuals, of whom 40 (41%) participants were enrolled in the GX-19 trial (20 [50%] in the 1·5 mg group and 20 [50%] in the 3·0 mg group). Between Dec 28 and 31, 2020, we screened 23 participants, of whom 21 (91%) participants were enrolled on the GX-19N trial. 32 (52%) of 61 participants reported 80 treatment-emergent adverse events after vaccination. All solicited adverse events were mild except one (2%) case of moderate fatigue in the 1·5 mg GX-19 group; no serious vaccine-related adverse events were detected. Binding antibody responses increased after second dose of vaccination in all groups (p=0·0002 in the 1·5 mg GX-19 group; p<0·0001 in the 3·0 mg GX-19; and p=0·0004 for the spike protein and p=0·0001 for the RBD in the 3·0 mg GX-19N group). INTERPRETATION: GX-19 and GX-19N are safe and well tolerated. GX-19N induces humoral and broad SARS-CoV-2-specific T-cell responses. GX-19N shows lower neutralising antibody responses and needs improvement to enhance immunogenicity. FUNDING: The Korea Drug Development Fund, funded by the Ministry of Science and ICT, Ministry of Trade, Industry, and Energy, and Ministry of Health and Welfare.

A high-specificity flap probe-based isothermal nucleic acid amplification method based on recombinant FEN1-Bst DNA polymerase.

The COVID-19 pandemic has unfortunately demonstrated how easily infectious diseases can spread and harm human life and society. As of writing, pandemic has now been on-going for more than one year. There is an urgent need for new nucleic acid-based methods that can be used to diagnose pathogens early, quickly, and accurately to effectively impede the spread of infections and gain control of epidemics. We developed a flap probe-based isothermal nucleic acid amplification method that is triggered by recombinant FEN1-Bst DNA polymerase, which-through enzymatic engineering-has both DNA synthesis, strand displacement and cleavage functions. This novel method offers a simpler and more specific probe-primer pair than those of other isothermal amplifications. We tested the method's ability to detect SARS-CoV-2 (both ORF1ab and N genes), rotavirus, and Chlamydia trachomatis. The limits of detection were 10 copies/µL for rotavirus, C. trachomatis, and SARS-CoV-2 N gene, and 100 copies/µL for SARS-CoV-2 ORF1ab gene. There were no cross-reactions among 11 other common pathogens with characteristics similar to those of the test target, and the method showed 100% sensitivity and 100% specificity in clinical comparisons with RT-PCR testing. In addition to real-time detection, the endpoint could be displayed under a transilluminator, which is a convenient reporting method for point-of-care test settings. Therefore, this novel nucleic acid senor has great potential for use in clinical diagnostics, epidemic prevention, and epidemic control.

A recombinant Lactobacillus plantarum strain expressing the spike protein of SARS-CoV-2.

Coronavirus disease 2019 (COVID-19), which is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has become a global pandemic in the past four months and causes respiratory disease in humans of almost all ages. Although several drugs have been announced to be partially effective treatments for this disease, no approved vaccine is available. Here, we described the construction of a recombinant Lactobacillus plantarum strain expressing the SARS-CoV-2 spike protein. The results showed that the spike gene with optimized codons could be efficiently expressed on the surface of recombinant L. plantarum and exhibited high antigenicity. The highest protein yield was obtained under the following conditions: cells were induced with 50 ng/mL SppIP at 37 °C for 6-10 h. The recombinant spike (S) protein was stable under normal conditions and at 50 °C, pH = 1.5, or a high salt concentration. Recombinant L. plantarum may provide a promising food-grade oral vaccine candidate against SARS-CoV-2 infection.

SARS-CoV-2 Reverse Genetics Reveals a Variable Infection Gradient in the Respiratory Tract.

The mode of acquisition and causes for the variable clinical spectrum of coronavirus disease 2019 (COVID-19) remain unknown. We utilized a reverse genetics system to generate a GFP reporter virus to explore severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pathogenesis and a luciferase reporter virus to demonstrate sera collected from SARS and COVID-19 patients exhibited limited cross-CoV neutralization. High-sensitivity RNA in situ mapping revealed the highest angiotensin-converting enzyme 2 (ACE2) expression in the nose with decreasing expression throughout the lower respiratory tract, paralleled by a striking gradient of SARS-CoV-2 infection in proximal (high) versus distal (low) pulmonary epithelial cultures. COVID-19 autopsied lung studies identified focal disease and, congruent with culture data, SARS-CoV-2-infected ciliated and type 2 pneumocyte cells in airway and alveolar regions, respectively. These findings highlight the nasal susceptibility to SARS-CoV-2 with likely subsequent aspiration-mediated virus seeding to the lung in SARS-CoV-2 pathogenesis. These reagents provide a foundation for investigations into virus-host interactions in protective immunity, host susceptibility, and virus pathogenesis.