Development and characterization of a fully humanized ACE2 mouse model.

Area of Science:

• * Molecular biology and virology
• * Animal modeling for infectious diseases
• * Genomics and transcriptomics

Background:

• * Existing mouse models of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection often fail to replicate human angiotensin-converting enzyme 2 (ACE2) protein expression, leading to inaccurate pathology representation.
• * A novel, fully humanized ACE2 (hACE2) mouse model was developed to overcome these limitations by replacing the mouse Ace2 locus with the complete human ACE2 gene and an upstream long noncoding RNA (LncRNA).

Purpose of the Study:

• * To characterize a novel fully humanized ACE2 (hACE2) mouse model for SARS-CoV-2 infection studies.
• * To compare the hACE2 model's ACE2 expression profile and response to SARS-CoV-2 infection with existing models (KRT18-ACE2, K18).
• * To investigate the role of the upstream LncRNA in ACE2 expression and function.

Main Methods:

• * Design and characterization of a fully humanized ACE2 (hACE2) mouse model.
• * Comparative analysis of ACE2 tissue expression, blood pressure, angiotensin II metabolism, and renal cortical transcriptome between hACE2, K18, and wild-type mice.
• * Intranasal infection of hACE2 and K18 mice with the SARS-CoV-2 beta variant, followed by monitoring of viral replication, inflammation, weight, survival, and immune response.
• * CRISPR-mediated disruption of the upstream LncRNA to assess its impact on ACE2 expression.

Main Results:

• * The hACE2 mouse model demonstrated an ACE2 tissue expression profile similar to human tissues, unlike the K18 model.
• * hACE2 mice exhibited normal physiological parameters (blood pressure, angiotensin II metabolism, renal transcriptome) and showed lung inflammation but not brain inflammation upon SARS-CoV-2 infection, with 100% survival up to 12 days post-infection and evidence of acquired immunity.
• * CRISPR disruption of the upstream LncRNA had minimal impact on ACE2 mRNA and protein levels, suggesting its limited role in this context.

Conclusions:

• * The developed hACE2 mouse model provides a more accurate platform for studying SARS-CoV-2 infection mechanisms, particularly concerning tissue-restricted ACE2 expression.
• * This model facilitates research into noncoding sequence variants and upstream LncRNAs relevant to human ACE2 function.
• * The hACE2 model is valuable for defining disease pathways and understanding co-morbidities associated with human ACE2 in SARS-CoV-2 infection.