Abstract Body (Do not enter title and authors here): Introduction
Myocarditis, defined as an inflammatory injury to the myocardium, is irreversible with a 20% fatality rate in 2 years and a 50% fatality rate in 5 years. The most common causes of myocarditis are viruses, such as influenza A (IAV). IAV is a cardiotropic virus that can disseminate from the lungs to infect heart tissue, particularly during severe infections. Despite the implications for public health, little is known about the underlying mechanisms by which IAV causes heart pathology.
Methods
To investigate the role of the novel E3 ligase TRIM47 in IAV-induced myocarditis, we utilized both in vitro and in vivo approaches. In vivo, wild-type (WT) and TRIM47 knockout (KO) mice were challenged intranasally with IAV to induce myocarditis. Survival, heart function (echocardiography), and cardiac pathology (histology, viral load by RT-PCR, cytokine levels by ELISA) were evaluated. In vitro, bone marrow-derived macrophages (BMDM) from WT and TRIM47 KO mice were infected with IAV and interferon production was detected by ELISA. To elucidate molecular mechanisms, co-immunoprecipitation and Western blotting were used to confirm TRIM47-MAVS interaction and ubiquitination patterns. Furthermore, recombinant protein expression, mutagenesis, and co-expression studies were used to map binding sites and identify specific ubiquitination types and sites on MAVS.
Results
TRIM47 KO mice exhibited significantly reduced survival rates compared to WT controls following IAV infection, along with higher viral loads, diminished type I interferon levels, and increased histopathological damage in lungs and hearts. Consistently, TRIM47 KO BMDMs produced substantially lower interferon levels upon IAV challenge. Mechanistically, TRIM47 was found to directly bind MAVS at an endogenous level and promoted the ubiquitination of MAVS, facilitating its aggregation and subsequent activating downstream antiviral signaling pathways.
Conclusions
Our findings establish macrophage expressed TRIM47 as a critical regulator of the innate immune response to IAV-induced myocarditis. This study provides the first in vivo evidence of TRIM47’s role in controlling IAV-induced myocarditis and highlights the TRIM47- MAVS axis as a promising therapeutic target for viral-associated cardiovascular diseases.