Quantatitive Analysis of Conserved Sites on the SARS-CoV-2 Receptor-Binding Domain to Promote Development of Universal SARS-Like Coronavirus Vaccines (preprint)

Although vaccines have been successfully developed and approved against SARS-CoV-2, it is still valuable to perform studies on conserved antigenic sites for preventing possible pandemic-risk of other SARS-like coronavirus in the future and prevalent SARS-CoV-2 variants. By antibodies obtained from convalescent COVID-19 individuals, receptor binding domain (RBD) were identified as immunodominant neutralizing domain that efficiently elicits neutralizing antibody response with on-going affinity mature. Moreover, we succeeded to define a quantitative antigenic map of neutralizing sites within SARS-CoV-2 RBD, and found that sites S2, S3 and S4 (new-found site) are conserved sites and determined as subimmunodominant sites, putatively due to their less accessibility than SARS-CoV-2 unique sites. P10-6G3, P07-4D10 and P05-6H7, respectively targeting S2, S3 and S4, are relatively rare antibodies that also potently neutralizes SARS-CoV, and the last mAbs performing neutralization without blocking S protein binding to receptor. Further, we have tried to design some RBDs to improve the immunogenicity of conserved sites. Our studies, focusing on conserved antigenic sites of SARS-CoV-2 and SARS-CoV, provide insights for promoting development of universal SARS-like coronavirus vaccines therefore enhancing our pandemic preparedness.

Clinical findings of 35 cases with novel coronavirus pneumonia outside of Wuhan (preprint)

Objective: We sought to investigate the clinical characteristics of patients with novel coronavirus pneumonia in Xiamen, which is a city in Fujian Province, China. Methods: From January 20, 2020, to March 4, 2020, the clinical characteristics of all patients confirmed with novel coronavirus pneumonia admitted to the First Affiliated Hospital of Xiamen University, which was the only designated hospital for cases of novel coronavirus pneumonia in Xiamen, were analyzed. Results: A total of 35 cases of novel coronavirus pneumonia were confirmed. Patients were divided into the general-ward admission group and the intensive-care-unit (ICU) admission group. The most commonly observed symptoms were fever (80%), cough (51%), expectoration (28%), and fatigue (23%). Compared with patients in the general-ward group, patients in the ICU group had a higher maximum body temperature, a longer duration of fever after admission, and more symptoms of systemic pain. Considering the laboratory findings, patients in the ICU group exhibited lower peripheral blood lymphocyte ratios and lymphocyte counts but higher C-reactive protein and lactate dehydrogenase levels. All patients were discharged without death, and no patients required invasive ventilation, continuous renal replacement therapy, or extracorporeal membrane oxygenation. Conclusion: Relative to patients with novel coronavirus pneumonia in Wuhan, the cases in Xiamen were less severe.

Serology characteristics of SARS-CoV-2 infection since the exposure and post symptoms onset (preprint)

Background Timely diagnosis of SARS-CoV-2 infection is the prerequisite for treatment and preventive quarantine. The serology characteristics and complement diagnosis value of antibody test to RNA test needs to be demonstrated. Method A patient cohort study was conducted at the first affiliated hospital of Zhejiang University, China. Serial sera of COVID-19 patients were collected and total antibody (Ab), IgM and IgG antibody against SARS-CoV-2 were detected. The antibody dynamics during the infection were described. Results The seroconversion rate for Ab, IgM and IgG in COVID-19 patients was 98.8% (79/80), 93.8% (75/80) and 93.8% (75/80), respectively. The first detectible serology marker is total antibody and followed by IgM and IgG, with a median seroconversion time of 15, 18 and 20 day post exposure (d.p.e) or 9, 10 and 12 days post onset, separately. The antibody levels increased rapidly since 6 d.p.o and accompanied with the decline of viral load. For patients in the early stage of illness (0-7d.p.o),Ab showed the highest sensitivity (64.1%) compared to the IgM and IgG (33.3% for both, p<0.001). The sensitivities of Ab, IgM and IgG detection increased to 100%, 96.7% and 93.3% two weeks later, respectively. Conclusions Typical acute antibody response is induced during the SARS-CoV-2 infection. The serology testing provides important complementation to RNA test for pathogenic specific diagnosis and helpful information to evaluate the adapted immunity status of patient. It should be strongly recommended to apply well-validated antibody tests in the clinical management and public health practice to improve the control of COVID-19 infection.

Characterization of the SARS-CoV-2 Spike in an Early Prefusion Conformation (preprint)

Pandemic coronavirus disease 2019 (COVID-19) is caused by the emerging severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), for which there are no efficacious vaccines or therapeutics that are urgently needed. We expressed three versions of spike (S) proteins--receptor binding domain (RBD), S1 subunit and S ectodomain--in insect cells. RBD appears monomer in solutions, whereas S1 and S associate into homotrimer with substantial glycosylation. The three proteins confer excellent antigenicity with six convalescent COVID-19 patient sera. Cryo-electron microscopy (cryo-EM) analyses indicate that the SARS-CoV-2 S trimer dominate in a unique conformation distinguished from the classic prefusion conformation of coronaviruses by the upper S1 region at lower position ~15 [A] proximal to viral membrane. Such conformation is proposed as an early prefusion state for the SARS-CoV-2 spike that may broaden the knowledge of coronavirus and facilitate vaccine development.