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

## TL;DR

This study shows that even with effective HIV treatment, chronic inflammation and aging-related issues persist due to ongoing immune activation and cell aging in monkeys.

## Contribution

The study identifies macrophage activation and cell senescence as key drivers of chronic inflammation in SIV-infected macaques on ART.

## Key findings

- Short-term ART reverses acute immune activation but long-term ART fails to suppress chronic inflammation.
- Persistent macrophage activation and inflammasome signaling are linked to vascular injury and aging in SIV-infected macaques.
- Senescence-associated secretory phenotype and thrombus formation are observed in arteries of ART-treated macaques.

## Abstract

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.

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.

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.

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.