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

Abstract

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.