Abstract P3119: Selectively Expressing Sars-Cov-2 Spike Protein S1 Subunit In Cardiomyocytes Induces Cardiac Hypertrophy In Mice

Abstract

Cardiac injury is common in hospitalized COVID-19 patients and portends poorer prognosis and higher mortality. To better understand how SARS-CoV-2 (CoV-2) damages the heart, it is critical to elucidate the biology of CoV-2 encoded proteins, each of which may play multiple pathological roles. HCoV-NL63 is another human coronavirus with a Spike protein (NL63-S) that also engages ACE2 for virus entry but is known to only cause moderate respiratory symptoms. By comparing the pathological effects of NL63-S and CoV-2 spike protein (CoV-2-S), we tested the hypothesis that CoV-2-S damages the heart by activating cardiomyocyte (CM) innate immune responses, which is independent of ACE2.We found that CoV-2-S and not NL63-S interacted with Toll-like receptor 4 (TLR4), a crucial pattern recognition receptor responsible for detecting pathogen and initiating innate immune responses. Our data show that the S1 subunit of CoV-2-S (CoV-2-S1) interacts with the extracellular leucine-rich repeats-containing domain of TLR4 and activates NF-kB. To investigate the possible pathological role of CoV-2-S1 in the heart, we generated constructs that express membrane-localized CoV-2-S1 (S1-TM) or HCoV-NL63-S1 (NLS1-TM). AAV9-mediated, selective expression of the S1-TM and not NLS1-TM in CMs caused heart dysfunction, induced hypertrophic remodeling, and elicited cardiac inflammation. In vitro, overexpressing S1-TM in cultured neonatal rat ventricular CMs induced hypertrophy, decreased Myh6 and increased IL-6 . In the ventricular biopsy of a deceased patient with COVID-19 associated myocarditis, Spike protein and TLR4 were detected in both CMs and non-CMs, and these two proteins were absent in a healthy pre-pandemic human heart. In the ventricular biopsy of a patient who died of modified RNA vaccine-associated myocarditis, the expression of Spike protein was only detected in a small fraction of CMs, and no obvious TLR4 signal was detected in CMs. Because CoV-2-S does not interact with murine ACE2, our study presents a novel ACE2-independent pathological role of CoV-2-S. Additionally, our data suggest that modified RNA vaccine unlikely causes myocarditis by directly transfecting the CMs.