Enhanced antigen presentation by macrophages promotes human atherosclerosis progression: therapeutic implications

Background and aims: Atherosclerosis is a chronic inflammatory disease of the arterial wall, where modified self-antigens cause sustained adaptive immune responses driven by clonal expansion of CD4+ effector T cells in situ. Although immune tolerance-inducing vaccination strategies show promise in animal models, their clinical translation is limited by the unclear role of adaptive immune responses in human atherosclerosis. Methods: RNA sequencing and immunohistochemistry were employed in human atherosclerotic plaques. Nuclear run-on, CRISPRi/a, RNA pull-down, ChIP-qPCR, and flow cytometry were utilized to investigate the lncRNA-dependent regulatory mechanism. Functional validation was performed in Apoe-/- mice through perivascular or intravenous siRNA delivery, as well as perivascular administration of macrophage-targeting lipid nanoparticles carrying dCas9-VP64 mRNA and the guide RNA. Results: Major histocompatibility complex class II (MHCII)-dependent antigen presentation pathways were progressively activated in lesional macrophages as human atherosclerosis advanced. This activation was associated with increased CIITA expression, driven by enhanced transcription of its antisense-lncRNA (CIITA-AS1) and alternative splicing generating a non-coding transcript. Knockdown of these two lncRNAs reduced MHCII levels in human macrophages, thereby suppressing co-cultured T-cell activation. Mechanistically, CIITA-AS1 transcription promoted CIITA expression through STAT1 recruitment. Enforcing antisense-strand transcription of Ciita in lesional macrophages up-regulated Ciita and MHCII expression, exacerbating atherosclerosis in mice. Conversely, inhibition of macrophage antigen presentation via siRNA-mediated Ciita silencing attenuated atherosclerosis by reducing T-cell-mediated inflammation. Conclusions: This study reveals that CIITA-induced antigen presentation in macrophages activates local T-cell inflammatory response, promoting plaque progression. Targeting this pathway may improve vaccination efficacy by creating anti-inflammatory niches within plaques, offering a novel therapeutic strategy for atherosclerosis.