Characteristics of replication and pathogenicity of SARS-CoV-2 Alpha and Delta isolates

• Published in: Virologica Sinica Vol. 37; no. 6; pp. 804 - 812
• Main Authors: Feng, Xiao-Li, Yu, Dandan, Zhang, Mi, Li, Xiaohong, Zou, Qing-Cui, Ma, Wentai, Han, Jian-Bao, Xu, Ling, Yang, Cuixian, Qu, Wang, Deng, Zhong-Hua, Long, Junyi, Long, Yanghaopeng, Li, Mingkun, Yao, Yong-Gang, Dong, Xing-Qi, Zeng, Jianxiong, Li, Ming-Hua
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.12.2022; The Authors. Publishing services by Elsevier B.V. on behalf of KeAi Communications Co. Ltd
• Subjects: Alpha; Angiotensin-Converting Enzyme 2; Animals; Caco-2 Cells; COVID-19 - virology; Cricetinae; Delta; hACE2 transgenic mice; Hamster; Humans; Mice; Mice, Transgenic; SARS-CoV-2; SARS-CoV-2 - pathogenicity; Spike Glycoprotein, Coronavirus; Variants of concern (VOC); Virulence; Alpha; SARS-CoV-2; Variants of concern (VOC); Delta; hACE2 transgenic mice; Hamster
• ISSN: 1995-820X; 1674-0769; 1995-820X
• DOI: 10.1016/j.virs.2022.09.007

The continuously arising of SARS-CoV-2 variants has been posting a great threat to public health safety globally, from B.1.17 (Alpha), B.1.351 (Beta), P.1 (Gamma), B.1.617.2 (Delta) to B.1.1.529 (Omicron). The emerging or re-emerging of the SARS-CoV-2 variants of concern is calling for the constant monitoring of their epidemics, pathogenicity and immune escape. In this study, we aimed to characterize replication and pathogenicity of the Alpha and Delta variant strains isolated from patients infected in Laos. The amino acid mutations within the spike fragment of the isolates were determined via sequencing. The more efficient replication of the Alpha and Delta isolates was documented than the prototyped SARS-CoV-2 in Calu-3 and Caco-2 ​cells, while such features were not observed in Huh-7, Vero E6 and HPA-3 ​cells. We utilized both animal models of human ACE2 (hACE2) transgenic mice and hamsters to evaluate the pathogenesis of the isolates. The Alpha and Delta can replicate well in multiple organs and cause moderate to severe lung pathology in these animals. In conclusion, the spike protein of the isolated Alpha and Delta variant strains was characterized, and the replication and pathogenicity of the strains in the cells and animal models were also evaluated. •SARS-CoV-2 Alpha and Delta variants are isolated in the clinical samples.•Amino acid mutations in the Spike of the variants are determined by sequencing.•Replication capacity is compared between the Alpha and Delta variants in cells.•Viral pathogenicity of the variants is characterized in mice and hamsters.