Persistent activation of monocytes/macrophages and cell senescence in SIV-infected macaques on ART.

INTRODUCTION: Despite effective viral suppression with antiretroviral therapy (ART), people living with HIV (PLWH) experience persistent inflammation, immune dysfunction, and premature onset of cardiovascular and aging-related comorbidities. The mechanisms driving this transition from acute immune activation to chronic inflammatory remodeling under viral suppression remain incompletely understood. Here, we leveraged a nonhuman primate model to characterize the longitudinal transcriptomic changes across key stages of SIV infection and ART. METHODS: To define the underlying mechanisms, we performed longitudinal transcriptomic profiling in peripheral blood mononuclear cells (PBMCs) from a cohort of simian immunodeficiency virus (SIV)-infected rhesus macaques spanning four key stages: pre-infection, acute infection, short-term ART, and long-term ART. RESULTS: Bulk RNA sequencing revealed dynamic immune remodeling across infection and treatment. Acute SIV infection induced robust antiviral and inflammatory programs, with upregulation of interferon-stimulated genes (ISGs), IL-27, JAK/STAT, and NF-κB signaling, coupled with suppression of T- and B-cell activation pathways. Short-term ART effectively reversed these transcriptional perturbations, restoring adaptive immune gene expression and reducing innate antiviral responses to near-baseline levels. In contrast, chronic SIV infection on long-term ART maintained viral suppression but was characterized by reactivation of innate immune pathways, including TLR2/TLR4/MYD88, NF-κB, and inflammasome (NLRP3/NLRP12, caspase-1) signaling, along with sustained macrophage activation, platelet/coagulation signaling, and senescence-associated secretory phenotype. Protein analyses confirmed persistent CASPASE-1 and NF-κB activation in spleen tissue. Pathologic evaluation of a carotid artery from an SIV-infected, long-term ART-treated macaque revealed macrophage-rich plaques with p21⁺ senescent cells with intraluminal thrombus formation, recapitulating key features of HIV-associated atherogenesis. CONCLUSION: While ART normalizes acute infection-induced immune dysregulation, chronic SIV infection sustains a chronic, macrophage- and TLR-driven inflammatory state linked to vascular injury and aging process regardless of long-term suppression of viremia. Targeting inflammasome, NF-κB, and senescence pathways may mitigate non-AIDS comorbidities in PLWH.