Modulating Autoimmunity against LDL: Development of a Vaccine against Atherosclerosis

Cross-species single-cell RNA sequencing reveals divergent phenotypes and activation states of adaptive immunity in human carotid and experimental murine atherosclerosis

AIMS

The distinct functions of immune cells in atherosclerosis have been mostly defined by pre-clinical mouse studies. Contrastingly, the immune cell composition of human atherosclerotic plaques and their contribution to disease progression are only poorly understood. It remains uncertain whether genetic animal models allow for valuable translational approaches.

METHODS AND RESULTS

Single-cell RNA-sequencing (scRNA-seq) was performed to define the immune cell landscape in human carotid atherosclerotic plaques. The human immune cell repertoire demonstrated an unexpectedly high heterogeneity and was dominated by cells of the T-cell lineage, a finding confirmed by immunohistochemistry. Bioinformatical integration with 7 mouse scRNA-seq data sets from adventitial and atherosclerotic vascular tissue revealed a total of 51 identities of cell types and differentiation states, of which some were only poorly conserved between species and exclusively found in humans. Locations, frequencies, and transcriptional programmes of immune cells in mouse models did not resemble the immune cell landscape in human carotid atherosclerosis. In contrast to standard mouse models of atherosclerosis, human plaque leucocytes were dominated by several T-cell phenotypes with transcriptional hallmarks of T-cell activation and memory formation, T-cell receptor, and pro-inflammatory signalling. Only mice at the age of 22 months partially resembled the activated T-cell phenotype. In a validation cohort of 43 patients undergoing carotid endarterectomy, the abundance of activated immune cell subsets in the plaque defined by multi-colour flow cytometry associated with the extent of clinical atherosclerosis.

CONCLUSION

Integrative scRNA-seq reveals a substantial difference in the immune cell composition of murine and human carotid atherosclerosis-a finding that questions the translational value of standard mouse models for adaptive immune cell studies. Clinical associations suggest a specific role for T-cell driven (auto-)immunity in human plaque formation and instability.

Anti-aging vaccines targeting senescent cells

The development of senomorphic drugs to attenuate the senescent phenotype and senolytics to clear pro-inflammatory senescent cells to treat aging-associated disorders is being hotly pursued. The effort is complicated by the fact that senescent cells play a constructive role in some cellular processes such as tissue repair and wound healing. However, concerns about efficacy, which senescent cells to target, and unwanted side effects have created potential roadblocks. Chimeric Antigen Receptor (CAR) T cells directed against urokinase-type plasminogen activator receptor (uPAR), which is expressed on at least a subset of senescent cells (SC) in atherosclerotic plaques and fibrotic livers, removed SC and improved glucose metabolism. A conventional vaccine targeting CD153-expressing senescent T-cells, also improved glucose metabolism in obese mice. Recent work to selectively target senescent cells associated with several pathologies has resulted in the creation of a peptide vaccine that primarily targets endothelial cells expressing high levels of GPNMB, recently identified as a biomarker of senescence. The vaccine reduces atherosclerotic plaque burden and metabolic dysfunction such as glucose intolerance in mouse models of obesity and atherosclerosis. For translation to humans the activity of the vaccine will need to be tightly controlled, as the target, GPNMB has multiple roles in normal physiology including acting to inhibit and possibly resolve inflammation. A promising alternative approach would be to use passive immunization with a monoclonal antibody directed against GPNMB.