SARS-CoV-2 nsp13, nsp14, nsp15 and orf6 function as potent interferon antagonists

ABSTRACT

The Coronavirus disease 2019 (COVID-19), which is caused by the novel SARS-CoV-2 virus, is now causing a tremendous global health concern. Since its first appearance in December 2019, the outbreak has already caused over 5.8 million infections worldwide (till 29 May 2020), with more than 0.35 million deaths. Early virus-mediated immune suppression is believed to be one of the unique characteristics of SARS-CoV-2 infection and contributes at least partially to the viral pathogenesis. In this study, we identified the key viral interferon antagonists of SARS-CoV-2 and compared them with two well-characterized SARS-CoV interferon antagonists, PLpro and orf6. Here we demonstrated that the SARS-CoV-2 nsp13, nsp14, nsp15 and orf6, but not the unique orf8, could potently suppress primary interferon production and interferon signalling. Although SARS-CoV PLpro has been well-characterized for its potent interferon-antagonizing, deubiquitinase and protease activities, SARS-CoV-2 PLpro, despite sharing high amino acid sequence similarity with SARS-CoV, loses both interferon-antagonising and deubiquitinase activities. Among the 27 viral proteins, SARS-CoV-2 orf6 demonstrated the strongest suppression on both primary interferon production and interferon signalling. Orf6-deleted SARS-CoV-2 may be considered for the development of intranasal live-but-attenuated vaccine against COVID-19.

KEYWORDS:

• COVID-19
• SARS-CoV-2
• interferon antagonist
• PLpro
• orf6

Acknowledgments

This study was partly supported by funding from the Health and Medical Research Fund (HMRF 17160652), Hong Kong Special Administrative Region; the Consultancy Service for Enhancing Laboratory Surveillance of Emerging Infectious Diseases and Research Capability on Antimicrobial Resistance for Department of Health of the Hong Kong Special Administrative Region Government; the Theme-Based Research Scheme (T11/707/15) of the Research Grants Council, Hong Kong Special Administrative Region; Sanming Project of Medicine in Shenzhen, China (No. SZSM201911014); and the High Level-Hospital Program, Health Commission of Guangdong Province, China; and the donations of Michael Seak-Kan Tong, the Shaw Foundation Hong Kong, Richard Yu and Carol Yu, May Tam Mak Mei Yin, Respiratory Viral Research Foundation Limited, Hui Ming, Hui Hoy and Chow Sin Lan Charity Fund Limited, Chan Yin Chuen Memorial Charitable Foundation, Marina Man-Wai Lee, the Hong Kong Hainan Commercial Association South China Microbiology Research Fund, the Jessie & George Ho Charitable Foundation, and Perfect Shape Medical Limited. The funding sources had no role in the study design, data collection, analysis, interpretation, or writing of the report.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Correction Statement

This article has been republished with minor changes. These changes do not impact the academic content of the article.