Sex-biased response to and brain cell infection by SARS-CoV-2 in a highly susceptible human ACE2 transgenic model

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Abstract

The COVID-19 pandemic is caused by SARS-CoV-2 infection. Human angiotensin-converting enzyme II (hACE2) has been identified as the receptor enabling SARS-CoV-2 host entry. To establish a mouse model for COVID-19, we generated transgenic mouse lines using the (HS4) 2 -pCAG-hACE2-HA-(HS4) 2 transgene cassette, which expresses HA-tagged hACE2 under control of the CAG promoter and is flanked by HS4 insulators. Expression levels of the hACE2 transgene are respectively higher in lung, brain and kidney of our CAG-hACE2 transgenic mice and relatively lower in duodenum, heart and liver. The CAG-hACE2 mice are highly susceptibility to SARS-CoV-2 infection, with 100 PFU of SARS-CoV-2 being sufficient to induce 87.5% mortality at 9 days post-infection and resulting in a sole (female) survivor. Mortality was 100% at the higher titer of 1000 PFU. At lower viral titers, we also found that female mice exposed to SARS-CoV-2 infection suffered much less weight loss than male mice, implying sex-biased responses to SARS-CoV-2 infection. We subjected neuronal cultures to SARS-CoV-2 pseudovirus infection to ascertain the susceptibilities of neurons and astrocytes. Moreover, we observed that expression of SARS-CoV-2 Spike protein alters the synaptic responses of cultured neurons. Our transgenic mice may serve as a model for severe COVID-19 and sex-biased responses to SARS-CoV-2 infection, aiding in the development of vaccines and therapeutic treatments for this disease.

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  1. SciScore for 10.1101/2021.05.04.441029: (What is this?)

    Please note, not all rigor criteria are appropriate for all manuscripts.

    Table 1: Rigor

    EthicsIACUC: All animal experiments were performed with the approval of the Academia Sinica Institutional Animal Care and Utilization Committee (IACUC Protocol No. 12-08-391) and in strict accordance with its guidelines and those of the Council of Agriculture Guidebook for the Care and Use of Laboratory Animals.
    Euthanasia Agents: Surviving mice after viral challenge were euthanized using carbon dioxide.
    Sex as a biological variablePlasmid constructions: Generation of hACE2 transgenic mice: For mice production, we super-ovulated 3-4 week-old C57BL/6J female mice with 3.75-5 i.u. of pregnant mare serum gonadotropin (PMSG, Sigma-Aldrich G4877), followed 46-h later by 3.75-5 i.u. of human chorionic gonadotropin (hCG, Sigma-Aldrich CG1063).
    Randomizationnot detected.
    BlindingAll recordings and analyses were conducted blind to the experiential conditions (i.e., HA tag or Spike protein expression).
    Power Analysisnot detected.
    Cell Line Authenticationnot detected.

    Table 2: Resources

    Antibodies
    SentencesResources
    Antibodies and respective dilutions are as follows: hACE2 (Abcam ab108209, 1:2500); HA (Cell Signaling #3725, 1:1000); and HSP90 (provided by Dr. Chung Wang, 1:5000) [16].
    HSP90
    suggested: None
    The following commercial antibodies were used as primary antibodies for immunostaining: rabbit anti-ACE2 (Abcam, ab108209); mouse anti-HA (Abcam, ab130275); and rabbit anti-HA (Cell Signaling, 3742).
    anti-HA
    suggested: None
    Neuronal cultures were then fixed for immunofluorescence staining as described previously [18, 19] using the following primary antibodies: rabbit anti-ACE2 (Abcam, ab108209); mouse anti-HA (Abcam, ab130275); rabbit anti-HA (Cell Signaling, 3742); mouse anti-MAP2 (Sigma,
    anti-ACE2
    suggested: None
    anti-MAP2
    suggested: None
    M4403); mouse anti-GFAP (Millipore, MAB3402); and rabbit anti-GFP (Invitrogen, A6455).
    anti-GFP
    suggested: (Molecular Probes Cat# A-6455, RRID:AB_221570)
    Experimental Models: Cell Lines
    SentencesResources
    Production of pseudotyped SARS-CoV-2 lentivirus: The pseudotyped SARS-CoV-2 lentivirus, which carries SARS-CoV-2 Spike protein as viral envelope protein, was generated by transiently transfecting HEK-293T cells with pCMV-ΔR8.91, pLAS2w.EGFP.
    HEK-293T
    suggested: CCLV Cat# CCLV-RIE 1018, RRID:CVCL_0063)
    Experimental Models: Organisms/Strains
    SentencesResources
    Plasmid constructions: Generation of hACE2 transgenic mice: For mice production, we super-ovulated 3-4 week-old C57BL/6J female mice with 3.75-5 i.u. of pregnant mare serum gonadotropin (PMSG, Sigma-Aldrich G4877), followed 46-h later by 3.75-5 i.u. of human chorionic gonadotropin (hCG, Sigma-Aldrich CG1063).
    C57BL/6J
    suggested: None
    SARS-CoV-2 infection: CAG-hACE2 transgenic or wild-type (WT) mice were anesthetized and intranasally challenged with SARS-CoV-2 TCDC#4 (hCoV-19/Taiwan/4/2020 obtained from Taiwan Centers of Disease Control; lot: IBMS20200819) in a volume of 100 μL of sterile PBS at the indicated plaque-forming units (PFU).
    SARS-CoV-2 infection: CAG-hACE2
    suggested: None
    Recombinant DNA
    SentencesResources
    Production of pseudotyped SARS-CoV-2 lentivirus: The pseudotyped SARS-CoV-2 lentivirus, which carries SARS-CoV-2 Spike protein as viral envelope protein, was generated by transiently transfecting HEK-293T cells with pCMV-ΔR8.91, pLAS2w.EGFP.
    pCMV-ΔR8.91
    suggested: None
    pLAS2w.EGFP
    suggested: None
    Puro and pcDNA3.1-nCoV-SΔ18.
    pcDNA3.1-nCoV-SΔ18
    suggested: None
    Software and Algorithms
    SentencesResources
    The resulting products were scanned on a QX200 Droplet Reader (Bio-Rad Laboratories), and the data was analyzed using QuantaSoft™ software (Bio-Rad Laboratories).
    Bio-Rad Laboratories
    suggested: (Bio-Rad Laboratories, RRID:SCR_008426)
    QuantaSoft™
    suggested: None
    The images were processed using Photoshop (Adobe) with minimal adjustment of brightness or contrast applied to the entire images.
    Photoshop
    suggested: (Adobe Photoshop, RRID:SCR_014199)
    Statistical analysis: Statistical analyses were carried out in Excel or GraphPad Prism 8.0 software.
    Excel
    suggested: None
    GraphPad Prism
    suggested: (GraphPad Prism, RRID:SCR_002798)

    Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).


    Results from LimitationRecognizer: An explicit section about the limitations of the techniques employed in this study was not found. We encourage authors to address study limitations.

    Results from TrialIdentifier: No clinical trial numbers were referenced.


    Results from Barzooka: We did not find any issues relating to the usage of bar graphs.


    Results from JetFighter: Please consider improving the rainbow (“jet”) colormap(s) used on pages 20, 21 and 22. At least one figure is not accessible to readers with colorblindness and/or is not true to the data, i.e. not perceptually uniform.


    Results from rtransparent:
    • Thank you for including a conflict of interest statement. Authors are encouraged to include this statement when submitting to a journal.
    • Thank you for including a funding statement. Authors are encouraged to include this statement when submitting to a journal.
    • No protocol registration statement was detected.

    Results from scite Reference Check: We found no unreliable references.


    About SciScore

    SciScore is an automated tool that is designed to assist expert reviewers by finding and presenting formulaic information scattered throughout a paper in a standard, easy to digest format. SciScore checks for the presence and correctness of RRIDs (research resource identifiers), and for rigor criteria such as sex and investigator blinding. For details on the theoretical underpinning of rigor criteria and the tools shown here, including references cited, please follow this link.