ABSTRACT
Little is known about specific viral factors responsible for the pathogenesis and pathophysiology of long COVID. Here we describe a conditional knock-in (cKI) mouse strain inducibly expressing Nsp12, an essential component of SARS-CoV-2 RNA-dependent RNA polymerase (RdRp). Induction of Nsp12 translation was dependent on co-treatment with inhibitors of the integrated stress response in vitro and in vivo. We show that Nsp12 has a biologically significant link to mitochondrial dysfunction in vivo. In vitro, ectopic Nsp12 expression suppressed mitochondrial function in primary lung epithelial cells isolated from Nsp12 cKI mice. This functionality was physiologically relevant because, although ectopic Nsp12 expression in mouse lungs did not induce pneumonia, it did decrease mitochondrial activity in the hearts of Nsp12 cKI mice over the short and long terms. Administration in vivo of an RdRp inhibitor, EIDD-2801, restored mitochondrial function in cardiomyocytes of Nsp12 cKI mice. Our data demonstrate that SARS-CoV-2 RdRp activity in the lungs leads to cardiac mitochondrial dysfunction in vivo, generating a phenotype resembling aspects of long COVID in humans. Therapeutic targeting of SARS-CoV-2 RdRp may thus represent a novel means of preventing or mitigating intense fatigue and/or myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS)-like disease caused by mitochondrial dysfunction in long COVID patients.