Surveillance of SARS-CoV-2 Antibody of Patients in Local Affected Area During the Lockdown (preprint)

Background: Serosurvalence is crucial in estimating the range of SARS-CoV-2 infections, predicting the possibility of another wave, and decide on a vaccination strategy. To understand the herd immunity after the COVID-19 pandemic, the seroprevalence was measured in 3062 individuals with or without COVID-19. Methods: The levels of SARS-CoV-2 antibody IgM and IgG were measured by the immuno-colloidal gold method.Results: The mean seroprevalence for IgM and IgG in all participants was 2.81% and 7.51%, respectively. The positive rate of IgG was significantly higher in women than in men (P<0.05). The highest positive rate of IgM was observed in 41-60 years of age (3.49%), while the highest seroprevalence for IgG was observed in persons >60 years of age (8.61%). The positive rates of IgM and IgG in the convalescent patients were 31.82% and 77.27%, respectively, which was significantly higher than individuals with suspected syndromes or individuals without any clinical signs (P<0.01). Seroprevalence for IgG in medical staff was markedly higher than those in residents. The seroprevalence in patients with various comorbidity was no significant difference (P>0.05).Conclusions: The low positive rate of the SARS-CoV-2 IgM and NA test indicated that the SARS-CoV-2 outbreak is subsiding after three months, and the possibility of reintroduction of the virus from an unidentified natural reservoir is low. Seroprevalence provides the information for humoral immunity and vaccine in the future.

Presence of SARS-CoV-2 RNAs in Exosomes from COVID‐19 Patients: Their Characterization and Prognostic Potential (preprint)

Aim: Exosomes are frequently used for characterization of diseases, e.g., viral infections, but have not been reported for COVID-19. The aims of our study were to determine exosomes’ novel applications for SARS-CoV-2 RNA infection and prognosis of COVID-19 disease.Methods: From 15 COVID-19 patients and five healthy controls, 32 serum samples were collected by clinicians in Wuhan, China. Exosomes were purified, their RNAs (exoRNAs) were isolated and analyzed using RT-PCR for the presence of the N and/or ORF1ab viral genes, and the human RNaseP gene as reference.Results: Exosomes showed their typical lipid bilayer structure between 30 to 150 nm in size. No viral RNAs were detected from the 5 healthy controls. From 4 patients (26.67% of the patients), only the viral N but not the ORF1ab genes was detected. However, intact viral particles were not observed in exosome samples from the four positive patients. Importantly, expression of the N gene was detected during the active or early-stages of the disease, and the expression levels gradually decreased from the critical to the mild patients (in reverse to their CT values): Patient 1 /critical/ progress/ (CT-value: 34.74), Patient 9/severe/progress (CT-value: 37.65), Patient 11/severe /progress (CT-value: 37.16), and Patient 15/mild/early stage (CT-value: 38.44). Among them, only patient 1 had received stem cell transfusion. Patients 9 and 11 demonstrated recurrence of SARS-CoV-2. Patient 15 was the earliest phase patient with the N gene.Conclusion: SARS-CoV-2 RNAs were detected in exosomes which came only from the 15 COVID-19 patients but not from the 5 healthy controls. In addition, the presence of the viral N gene showed association with severity in the disease. Our novel discovery indicates that SARS-CoV-2 RNAs in serum exosomes can be used to complement existing assays for characterization of the SARS-CoV-2 infection and for prognosis of the COVID-19 disease.Funding Statement: This study was funded by National Natural Science Foundation of China (Grant No. 81702273), the Key Project for Anti-2019 Novel Coronavirus Pneumonia from the National Key Research and Development Program of China (Grant No. 2020YFC0845500), the National Key Research and Development Program of China (Grant No. 2018YFE0204500), Science and technology key project of Guangdong Province: Study on the source and epidemiology of COVID-19 (No.2020B111107001), the Scientific research project of COVID-19 epidemic prevention and control in Guangdong universities (No.2020KZDZX1087), and the Zhongnan Hospital of Wuhan University Science, Technology and Innovation Seed Fund, Project znpy2018117 and znpy2019064.Declaration of Interests: We declare no competing interests.Ethics Approval Statement: The study was reviewed and approved by Medical Ethics Committee Zhongnan Hospital of Wuhan University in the Scientific Research project No 2020066.

Serological immunochromatographic approach in diagnosis with SARS-CoV-2 infected COVID-19 patients (preprint)

An outbreak of new coronavirus SARS-CoV-2 was occurred in Wuhan, China and rapidly spread to other cities and nations. The standard diagnostic approach that widely adopted in the clinic is nuclear acid detection by real-time RT-PCR. However, the false-negative rate of the technique is unneglectable and serological methods are urgently warranted. Here, we presented the colloidal gold-based immunochromatographic (ICG) strip targeting viral IgM or IgG antibody and compared it with real-time RT-PCR. The sensitivity of ICG assay with IgM and IgG combinatorial detection in nuclear acid confirmed cases were 11.1%, 92.9% and 96.8% at the early stage (1-7 days after onset), intermediate stage (8-14 days after onset), and late-stage (more than 15 days), respectively. The ICG detection capacity in nuclear acid-negative suspected cases was 43.6%. In addition, the consistencies of whole blood samples with plasma were 100% and 97.1% in IgM and IgG strips, respectively. In conclusion, serological ICG strip assay in detecting SARS-CoV-2 infection is both sensitive and consistent, which is considered as an excellent supplementary approach in clinical application.