Multiomics profiling unravels T cells as master regulators of antibacterial immune responses to infective endocarditis
R Kaiser, R Dewender, M Joppich, M Schmid, L Kaeaeb, R Escaig, C Gold, A Akhalkatsi, A Droste zu Senden, C Hagl, S Massberg, K Stark, L Nicolai, K Martinod, K PekayvazAbstract
Background
Infective endocarditis (IE) is among the most prevalent pathogen-induced cardiovascular disease entities. While the incidence of IE has doubled during the past two decades, treatment options remain restricted to antibiotics and surgical valve repair. Still, patients with IE suffer from high morbidity and mortality rates, highlighting the urgent need for therapeutic innovation. Our understanding of systemic immune responses to IE is limited, and most pathophysiological insights described thus far are restricted to histological studies in rodents. Here, we enrolled patients with clinically confirmed infective endocarditis in a prospective, longitudinal, and multicenter immunophenotyping study to profile the systemic host response to IE. By reverse translational approaches, we confirm the fundamental role of T cells as master regulators of IE.
Methods
We used clinical data and multiomics profiling, including scRNAseq of PBMCs, plasma proteomics and flow cytometry, to identify IE-specific immune responses. In vitro assays of neutrophil activation along with the novel “vegetation-on-a-chip” assay were used to mechanistically validate IE-specific molecular targets. A translationally relevant murine IE model was used to underline T cells as crucial modulators of IE-directed immune responses.
Results
Immune fluorescence stainings revealed abundant infiltration of T cells in the paravalvular niche of infected valves. Further, profiling of circulating T cells in IE patients showed strong activation of circulating CD4+ and CD8+ T cell subsets. Comparing IE patients to both healthy controls and patients with non-cardiac bacterial infections using scRNAseq, we detected the upregulation of endocarditis-specific circulating factors, including high plasma levels of complement factors and the expansion of T cell clusters in IE. Among these clusters, we revealed circulating T cell subsets characterized by a pro-inflammatory phenotype that upregulate IE-specific transcriptional programs with elevated cytokine expression. In vitro, we used a novel vegetation-on-a-chip assay to confirm that in an IE-like microenvironment, soluble T cell factors activate myeloid cells and facilitate bacterial clearance through myeloid cell activation. Finally, T cell depletion in a translationally relevant mouse model of Staphylococcus aureus-induced IE aggravated disease severity and mortality, highlighting T cells as master regulators of the myeloid response to bacterial IE.
Conclusions
These data provide the first in-depth immune landscape of human IE and provide mechanistic evidence of an unexpectedly fundamental role of T cells in mounting the endocarditis-specific host defense by orchestrating neutrophil responses. Our study further provides the first comprehensive immune landscape of human IE, representing a crucial resource for the development of novel immunomodulatory treatment approaches in this insidious disease.Figure 1Figure 2