Q493K and Q498H substitutions in Spike promote adaptation of SARS-CoV-2 in mice

Abstract

Background: An ideal animal model to study SARS-coronavirus 2 (SARS-CoV-2) pathogenesis and evaluate therapies and vaccines should reproduce SARS-CoV-2 infection and recapitulate lung disease like those seen in humans. The angiotensin-converting enzyme 2 (ACE2) is a functional receptor for SARS-CoV-2, but mice are resistant to the infection because their ACE2 is incompatible with the receptor-binding domain (RBD) of the SARS-CoV-2 spike protein .Methods: SARS-CoV-2 was passaged in BALB/c mice to obtain mouse-adapted virus strain. Complete genome deep sequencing of different generations of viruses was performed to characterize the dynamics of the adaptive mutations in SARS-CoV-2. Indirect immunofluorescence analysis and Biolayer interferometry experiments determined the binding affinity of mouse-adapted SARS-CoV-2 WBP-1 RBD to mouse ACE2 and human ACE2. Finally, we tested whether TLR7/8 agonist Resiquimod (R848) could also inhibit the replication of WBP-1 in the mouse model. Findings: The mouse-adapted strain WBP-1 showed increased infectivity in BALB/c mice and led to severe interstitial pneumonia. We characterized the dynamics of the adaptive mutations in SARS-CoV-2 and demonstrated that Q493K and Q498H in RBD significantly increased its binding affinity towards mouse ACE2. Additionally, the study tentatively found that the TLR7/8 agonist Resiquimod was able to protect mice against WBP-1 challenge. Therefore, this mouse-adapted strain is a useful tool to investigate COVID-19 and develop new therapies. Interpretation: We found for the first time that the Q493K and Q498H mutations in the RBD of WBP-1 enhanced its interactive affinities with mACE2. The mouse-adapted SARS-CoV-2 provides a valuable tool for the evaluation of novel antiviral and vaccine strategies. This study also tentatively verified the antiviral activity of TLR7/8 agonist Resiquimod against SARS-CoV-2 in vitro and in vivo.

But Mouse, you are not alone: On some severe acute respiratory syndrome coronavirus 2 variants infecting mice

“…Further details are provided under Supplementary Methods for Molecular Modelling. We then compared our insilico findings with experimental results reported by different research groups with mouse adapted strains/isolates [6][7][8]13,[21][22][23][24][25][26][27][28][29] and VOC 14,[30][31][32][33][34] (Table 1). Taken together, we were able to gain valuable insights into the likely effects of different mutations of consequence.…”

ACE2 is the critical in vivo receptor for SARS-CoV-2 in a novel COVID-19 mouse model with TNF- and IFNγ-driven immunopathology

“…However, K18-hACE2 mice are overly susceptible as they develop deadly SARS-CoV-2 encephalitis (in addition to pneumonia) in response to low infection doses, due to non-physiological and broad (over)expression of hACE2 (Kumari et al, 2021). Recently, four mouse-adapted SARS-CoV-2 strains have been generated by either genetic engineering (Dinnon et al, 2020) and/or serial passaging (Gu et al, 2020; Huang et al, 2021; Leist et al, 2020). However, while infectivity is achieved with all of these strains, only two (Huang et al, 2021; Leist et al, 2020) cause a pathology that mimics human disease, and pathological mechanisms are still poorly understood.…”

A lethal mouse model using a mouse-adapted SARS-CoV-2 strain with enhanced binding to mouse ACE2 as an important platform for COVID-19 research

“…In addition to in vitro and ex vivo culture systems, readily available animal models are essential to facilitate the investigation of the pathogenesis and transmission, as well as the evaluation of antivirals and vaccine candidates for this major threat to global health [3À5]. In a recent study published in EBioMedicine, Huang et al reports the generation of a lethal mouse model for COVID-19 by intranasally inoculating Balb/c mice with a mouse-adapted SARS-CoV-2 strain which is capable of utilizing mouse angiotensin-converting enzyme II (ACE2) for cell entry [6].…”

“…As demonstrated by Huang et al, another strategy for developing mouse model for COVID-19 is by adapting SARS-CoV-2 in mice. Through serial passages of wild-type SARS-CoV-2 in mouse lungs, the group generated a mouse-adapted virus strain (WBP-1) that consistently causes severe interstitial pneumonia and death in Balb/c mice intranasally challenged with 10 5 plaque-forming units of the virus [6]. The Q498H mutation emerged after only one passage, while the Q493K mutation started to appear in passage 5, which likely contributed to the high pathogenicity of WBP-1 in mice.…”

“…Some of these variants are considered to be "variants of concerns" as they may be associated with enhanced transmission, pathogenicity, and/or immune evasion [1]. In the presented study, Huang et al characterized the adaptive mutations of the mouse-adapted WBP-1 strain and identified Q493K and Q498H in the SARS-CoV-2 spike receptor-binding domain as two key mutations associated with enhanced binding affinity towards mACE2 [6]. These results are particularly relevant to the control of the ongoing COVID-19 pandemic because the presence of these and other mutations that may facilitate binding with the ACE2 of mice and/or other animal species in clinical SARS-CoV-2 variants may suggest the need for tightened source control in order to minimize the contacts between humans and these potentially infected animal species leading to interspecies transmission.…”