Arrhythmogenic mechanisms of acute cardiac infection

Cardiovascular disease is the leading cause of death world-wide, with 42% of sudden cardiac death in young adults caused by myocarditis. Viruses represent the main cause of myocarditis, with adenovirus being a leading pathogen. However, it is not understood how adenoviruses cause sudden cardiac arrest. Myocarditis is defined by two phases, acute and chronic. The acute phase involves viral-mediated remodeling of subcellular structures in the myocardium, which is thought to contribute to arrhythmogenesis. The chronic phase is immune response-mediated, where the host immune system causes damage that induces gross remodeling of the heart, which can result in cardiac arrest or heart failure. Electrical impulses of the heart are propagated by cardiomyocytes, via gap junctions, ion channels, and intracellular junctions, creating the healthy heartbeat. Cx43, the primary gap junction protein in the myocardium, not only propagates electrical signals, but also anti-viral molecules. Viral targeting of gap junction function leads to reduced anti-viral responses in neighboring cells. However, reduced cellular communication would dangerously alter cardiac conduction. Using a cardiotropic adenovirus, MAdV-3, we find that viral genomes are significantly enriched in the heart, with a decrease of gap junction and ion channel mRNA in infected hearts, however, their protein levels were unchanged. Phosphorylation of Cx43 at serine 368, known to reduce gap junction open probability, was increased in infected hearts. Ex vivo optical mapping illustrated decreased conduction velocity in the infected heart and patch clamping of isolated cardiomyocytes revealed prolonged action potential duration, along with decreased potassium current density during infection. Pairing mouse work with human induced pluripotent stem cell-derived cardiomyocytes, we found that human adenovirus type-5 infection increased pCx43-Ser368 and perturbation of intercellular coupling, as we observed with in vivo MAdV-3 infection. Allowing adenovirus infection to progress in vivo, we find myocardium remodeling and immune cell infiltration. Together, these data demonstrate the complexity of cardiac infection from viral-infection induced subcellular alterations in electrophysiology to immune-mediated cardiomyopathy of cardiac adenoviral infection. Our data describe virally induced mechanisms of arrhythmogenesis, which could lead to the development of new diagnostic tools and therapies, to help protect patients from arrhythmia following infection.