Murine CMV infection unmasks macrophage-driven inflammatory cardiomyopathy in Pkp2 , but not in Ttn mutant mice

2. Background Genetic cardiomyopathies display variable penetrance and phenotypic expression, highlighting the influence of environmental modulators. Myocarditis, commonly triggered by cardiotropic viruses, overlaps clinically with genetic cardiomyopathies. Consequently, these infections are implicated as secondary factors that accelerate disease onset and progression, yet their precise impact in specific genetic settings remains unexplored. Methods To interrogate this, genetic mouse models heterozygous for a mutant allele of desmosomal plakophilin-2 ( Pkp2 +/− ) or sarcomeric titin ( Ttn +/− ), genes frequently linked to acute myocarditis, were challenged with murine cytomegalovirus (MCMV) to determine how latent infection influences myocardial inflammation, tissue remodeling, and cardiac performance. Integrated experimental approaches, including echocardiography, histology, flow cytometry, single-cell RNA sequencing, as well as cytokine and kinome analyses, defined immune and signaling responses in infected versus non-infected hearts. Results Acute, MCMV-induced viral myocarditis and subsequent latent MCMV infection unmasked early disease onset in Pkp2 +/− animals, leading to progressive systolic impairment, whereas in Ttn +/− mice cardiac structure and function remained preserved throughout infection. Cardiac immune profiling uncovered infection- and genotype-specific divergence: both genetic models showed a stable myocardial effector-memory CD8 + T-cell response to MCMV, but only Pkp2 +/− hearts recruited additional Ly6C + CCR2 + monocytes and macrophages with distinct inflammatory signatures. In the absence of infection, Pkp2 insufficiency initiated subclinical CCL2 secretion and subsequent recruitment of CCR2 + cells, reflecting early immune activation preceding age-associated functional and structural decline. At this stage, cytokine and kinase evaluations indicated a balance between proinflammatory and compensatory signals. However, with aging or following MCMV challenge, this balance shifted towards persistent inflammation, evidenced by chronic upregulation of cytokines and activation of signaling pathways, which ultimately led to adverse effects and myocardial dysfunction. Conclusions Manifestation of genetic cardiomyopathies depends on interactions between inherited susceptibility and environmental stressors. Here, we show that cytomegalovirus infection intensifies inflammation in PKP2 -related cardiomyopathy. In contrast, TTN -linked cardiomyopathy does not exhibit increased inflammation under the same conditions. For individuals carrying desmosomal variants, infection control and tailored anti-inflammatory strategies may attenuate or delay disease manifestation and progression.