Inhibitors of endosomal acidification suppress SARS-CoV-2 replication and relieve viral pneumonia in hACE2 transgenic mice

Chao Shang,Jianan Cong,Chenchen Ge,Yilong Zhu,Tingyu Li,Yiquan Li,Xiao Li,Mingyao Tian,Xinyu Zhuang,He Zhang,Jing Lu,Ningyi Jin

doi:10.1186/s12985-021-01515-1

Abstract

BackgroundCoronavirus disease 2019 (COVID-19) is caused by SARS-CoV-2 and broke out as a global pandemic in late 2019. The acidic pH environment of endosomes is believed to be essential for SARS-CoV-2 to be able to enter cells and begin replication. However, the clinical use of endosomal acidification inhibitors, typically chloroquine, has been controversial with this respect.MethodsIn this study, RT-qPCR method was used to detect the SARS-CoV-2N gene to evaluate viral replication. The CCK-8 assay was also used to evaluate the cytotoxic effect of SARS-CoV-2. In situ hybridization was used to examine the distribution of the SARS-CoV-2 gene in lung tissues. Hematoxylin and eosin staining was also used to evaluate virus-associated pathological changes in lung tissues.ResultsIn this study, analysis showed that endosomal acidification inhibitors, including chloroquine, bafilomycin A1 and NH4CL, significantly reduced the viral yields of SARS-CoV-2 in Vero E6, Huh-7 and 293T-ACE2 cells. Chloroquine and bafilomycin A1 also improved the viability and proliferation of Vero E6 cells after SARS-CoV-2 infection. Moreover, in the hACE2 transgenic mice model of SARS-CoV-2 infection, chloroquine and bafilomycin A1 reduced viral replication in lung tissues and alleviated viral pneumonia with reduced inflammatory exudation and infiltration in peribronchiolar and perivascular tissues, as well as improved structures of alveolar septum and pulmonary alveoli.ConclusionsOur research investigated the antiviral effects of endosomal acidification inhibitors against SARS-CoV-2 in several infection models and provides an experimental basis for further mechanistic studies and drug development.

Highlights

Coronavirus disease 2019 (COVID-19) is caused by SARS-CoV-2 and broke out as a global pandemic in late 2019
Inhibitors of endosomal acidification improved the viability of Vero E6 cells after SARS‐CoV‐2 infection The infection dose and timing of SARS-CoV-2 infection were determined in Vero E6 cells using CCK-8 assays
Colony assays showed that chloroquine and bafilomycin A1 improved cell proliferation in Vero E6 cells infected with SARS-CoV-2 (Fig. 1f )

Summary

Introduction

Coronavirus disease 2019 (COVID-19) is caused by SARS-CoV-2 and broke out as a global pandemic in late 2019. Coronavirus disease 2019 (COVID-19) emerged in late 2019 and spread rapidly to become a global pandemic, posing significant threat to human health. This pathogen was officially named by World Health Organization (WHO) as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). In order to begin viral replication, Shang et al Virol J (2021) 18:46 there are two essential requirements: endosomal acidification and the pH-dependent cleavage of viral glycoprotein segments by endosomal proteases. Without these processes, the virus cannot enter cells and replication is abolished [5]. Agents that target endosomal acidification may represent potential antiviral approaches in the fight against SARS-CoV-2 [6]

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