Attenuation and restoration of severe acute respiratory syndrome coronavirus mutant lacking 2'-o-methyltransferase activity.

Abstract

UNLABELLED:

The sudden emergence of severe acute respiratory syndrome coronavirus (SARS-CoV) in 2002 and, more recently, Middle Eastern respiratory syndrome CoV (MERS-CoV) underscores the importance of understanding critical aspects of CoV infection and pathogenesis. Despite significant insights into CoV cross-species transmission, replication, and virus-host interactions, successful therapeutic options for CoVs do not yet exist. Recent identification of SARS-CoV NSP16 as a viral 2'-O-methyltransferase (2'-O-MTase) led to the possibility of utilizing this pathway to both attenuate SARS-CoV infection and develop novel therapeutic treatment options. Mutations were introduced into SARS-CoV NSP16 within the conserved KDKE motif and effectively attenuated the resulting SARS-CoV mutant viruses both in vitro and in vivo. While viruses lacking 2'-O-MTase activity had enhanced sensitivity to type I interferon (IFN), they were not completely restored in their absence in vivo. However, the absence of either MDA5 or IFIT1, IFN-responsive genes that recognize unmethylated 2'-O RNA, resulted in restored replication and virulence of the dNSP16 mutant virus. Finally, using the mutant as a live-attenuated vaccine showed significant promise for possible therapeutic development against SARS-CoV. Together, the data underscore the necessity of 2'-O-MTase activity for SARS-CoV pathogenesis and identify host immune pathways that mediate this attenuation. In addition, we describe novel treatment avenues that exploit this pathway and could potentially be used against a diverse range of viral pathogens that utilize 2'-O-MTase activity to subvert the immune system.

IMPORTANCE:

Preventing recognition by the host immune response represents a critical aspect necessary for successful viral infection. Several viruses, including SARS-CoV, utilize virally encoded 2'-O-MTases to camouflage and obscure their viral RNA from host cell sensing machinery, thus preventing recognition and activation of cell intrinsic defense pathways. For SARS-CoV, the absence of this 2'-O-MTase activity results in significant attenuation characterized by decreased viral replication, reduced weight loss, and limited breathing dysfunction in mice. The results indicate that both MDA5, a recognition molecule, and the IFIT family play an important role in mediating this attenuation with restored virulence observed in their absence. Understanding this virus-host interaction provided an opportunity to design a successful live-attenuated vaccine for SARS-CoV and opens avenues for treatment and prevention of emerging CoVs and other RNA virus infections.

• Authors: Vineet D Menachery, Boyd L Yount Jr, Laurence Josset, Lisa E Gralinski, Trevor Scobey, Sudhakar Agnihothram, Michael G Katze, Ralph S Baric
• Journal: Journal of virology (J Virol) Vol. 88 Issue 8 Pg. 4251-64 (Apr 2014) ISSN: 1098-5514 [Electronic] United States
• PMID: 24478444 (Publication Type: Journal Article, Research Support, N.I.H., Extramural)

Chemical References

• Adaptor Proteins, Signal Transducing
• Carrier Proteins
• Ifit1 protein, mouse
• RNA-Binding Proteins
• Viral Nonstructural Proteins
• Methyltransferases
• Nsp16 protein, SARS virus
• Ifih1 protein, mouse
• DEAD-box RNA Helicases
• Interferon-Induced Helicase, IFIH1

Topics

• Adaptor Proteins, Signal Transducing
• Amino Acid Motifs
• Animals
• Carrier Proteins (genetics, metabolism)
• DEAD-box RNA Helicases (genetics, metabolism)
• Female
• Humans
• Interferon-Induced Helicase, IFIH1
• Male
• Methyltransferases (chemistry, genetics, metabolism)
• Mice
• Mice, Inbred BALB C
• Mice, Inbred C57BL
• Mutation
• RNA-Binding Proteins
• Severe acute respiratory syndrome-related coronavirus (enzymology, genetics, pathogenicity, physiology)
• Severe Acute Respiratory Syndrome (genetics, metabolism, virology)
• Viral Nonstructural Proteins (chemistry, genetics, metabolism)
• Virulence
• Virus Replication