Impact pathogenicity of SARS-CoV-2

The impact pathogenicity of SARS-CoV-2. Heneghan C

Published on August 3, 2020

Reference Hangping Yao, Xiangyun Lu, Qiong Chen et al. Patient-derived mutations impact pathogenicity of SARS-CoV-2 medRxiv; 2020. DOI: 10.1101/2020.04.14.20060160.
Study type
Country China
Setting Hospital
Funding Details Major Project of Zhejiang Provincial Science and Technology Department, National Science and Technology Major Project for the Control and Prevention of Major Infectious Diseases in China, and start-up funds from Life Sciences Institute at Zhejiang University.
Transmission mode Orofecal, Droplet

Bottom Line

Viable viral isolates were extracted from sputum (n=7), stool samples (n=3) and  one nasopharyngeal sample  indicating that the SARS-CoV-2 is capable of replicating in stool samples

Evidence Summary

Eleven SARS-CoV-2 viral isolates were obtained from patients admitted to Zhejiang University-affiliated hospitals in Hangzhou, China,

Three of the viable viral isolates were extracted from stool samples, indicating that the SARS-CoV-2 is capable of replicating in stool samples

Super-deep sequencing of the 11 viral isolates identified 1-5 mutations in the coding sequences. 

At 8 hours post-infection significant decreases in Ct value (increases in viral load) for five isolates were observed.  At 24 hours significant decreases in the Ct values for all of the viral isolates were observed.

What did they do?

The samples of the 11 patients involved in this study were collected during the early phase of the COVID-19 break out in China, dates ranging from 2nd of January to the 2nd of April 2020.

All except one of the patients had moderate or worse symptoms. Three patients had co-morbidities and one patient needed ICU treatment. Seven patients had sputum samples, one nasopharyngeal and three had stool samples 

The samples were pre-processed by mixing with appropriate volume of MEM medium with 2% FBS, Amphotericin B, Penicillin G, Streptomycin , and TPCK-trypsin. The supernatant was collected after centrifugation at 3000 rpm at room 434 temperature. Before infecting Vero-E6 cells, all collected supernatant was filtered using a 435 0.45 µm filter to remove cell debris etc.

Vero-E6 cells were infected with 11 viral isolates and quantitatively assessed their viral load at 1, 2, 4, 8, 24, and 48 hours post-infection (PI) and their viral cytopathic effects (CPE) at 48 and 72 hours PI. and examined whether the viral isolates could successfully bind to Vero-E6 243 cells as expected.  Super-deep sequencing of the 11 viral isolates on the Novaseq 6000 platform was performed  

Study reliability

Clearly defined setting Demographic characteristics described Follow-up length was sufficient Transmission outcomes assessed Main biases are taken into consideration
Yes Unclear Yes Yes Yes

What else should I consider?

This study requires replication as it provides direct evidence that mutations currently occurring in the SARS-CoV-2 genome have the functional potential to impact the viral pathogenicity. Viral surveillance should be also performed at the cellular level when possible.

About the authors

Carl Heneghan

Carl Heneghan

Carl is Professor of EBM & Director of CEBM at the University of Oxford. He is also a GP and tweets @carlheneghan. He has an active interest in discovering the truth behind health research findings