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In vivo, HIV-1 replicates within tissues, yet the impact of three-dimensional (3D) environments on viral spread remains unclear. Our laboratory previously showed that collagen-rich 3D extracellular matrix (ECM) imposes an Environmental Restriction to cell-free Virus Infectivity (ERVI). Here, we demonstrate that ERVI is mediated by adhesive ECM components assembled into tissue-like scaffolds. Transient interactions with collagen fibers rapidly diminish virion infectivity across diverse primary strains by impairing virus fusogenicity. Notably, collagen-experienced particles also induce a distinct antiviral transcriptional program and strong pro-inflammatory cytokine secretion in monocyte-derived macrophages. Mechanistically, collagen contact induces conformational changes in the viral glycoprotein Env, enhances its interaction with toll-like receptor 2 (TLR2), and promotes trafficking into TLR8-positive endosomes, thereby amplifying innate immune sensing. Thus, ERVI functions through a dual mechanism: reducing virion fusogenicity while increasing innate immune detection. These findings identify the biophysical properties of the ECM as a tissue-intrinsic arm of antiviral innate immunity. Collagen based 3D tissue-like cultures have been shown to modulate HIV-1 infectivity and mode of spread. Here, the authors demonstrate that varying the density of type I collagen matrices impair HIV-1 particle fusion and sensitize virions for TLR-based innate immune recognition by macrophages implicating structural changes in Env, TLR2 interaction and TLR8 positive endosomes promoting innate immune detection of viral gRNA.

Lipid-driven inflammation contributes to the development of atherosclerosis, and regulatory T cells (Tregs) have been proposed to influence macrophage responses to lipid stress. While adoptive Treg transfer has been shown to be safe in clinical studies, the mechanisms by which Tregs modulate macrophage lipid handling remain incompletely understood. In this study, we investigated the effects of ex vivo–expanded human Tregs on primary monocyte-derived M2-like macrophages exposed to oxidized low-density lipoprotein (oxLDL) in an in vitro coculture system. We assessed macrophage phenotype, gene expression, and cholesterol accumulation using flow cytometry, RNA sequencing, and western blotting. Our data show that coculture with Tregs attenuated oxLDL-induced pro-inflammatory responses and reduced intracellular lipid accumulation in macrophages. Mechanistically, we found evidence that Tregs transfer cyclic AMP (cAMP) into macrophages, which enhanced the ABCA1-mediated cholesterol efflux pathway and increased expression of paraoxonase-1 (PON1). These findings provide mechanistic insight into how Tregs modulate macrophage responses to oxLDL under controlled in vitro conditions. They highlight potential pathways through which Tregs may regulate macrophage lipid metabolism and inflammatory activity. Further in vivo studies will be essential to determine the physiological significance and therapeutic potential of these mechanisms.

The HIV-1 Rev-RRE regulatory axis plays a crucial role in viral replication by facilitating the nucleo-cytoplasmic export and expression of viral mRNAs with retained introns. In this study, we investigated the impact of variation in Rev-RRE functional activity on HIV-1 replication kinetics and reactivation from latency. Using a novel HIV-1 viral vector with an interchangeable Rev cassette, we engineered viruses with two diverse Rev functional activities and demonstrated that higher Rev-RRE activity confers greater viral replication capacity while maintaining a constant level of Nef expression. In addition, a low Rev activity virus rapidly acquired a compensatory mutation in the RRE that significantly increased Rev-RRE activity and replication. In a latency model, proviruses with differing Rev-RRE activity levels varied in the efficiency of viral reactivation, affecting both initial viral release and subsequent replication kinetics. These results demonstrate that activity differences in the Rev-RRE axis among different viral isolates have important implications for HIV replication dynamics and persistence. Importantly, our findings indicate that bolstering Rev/RRE activity could be explored as part of latency reversal strategies in HIV cure efforts. SummaryThe activity of the HIV-1 Rev-RRE axis is essential for viral replication and varies among primary viral isolates. However, the role of this for viral fitness, evolution, and persistence has not previously been investigated. Our results show that during in vitro replication, there is a selective fitness advantage for a virus with higher Rev-RRE activity and that HIV has the ability to fine-tune this regulatory system with minimal sequence changes. Additionally, the maintenance of Nef expression in a low Rev activity virus suggests a potential mechanism for balancing immune evasion and replication capacity in different selection landscapes within a host. We also show that the virus with low Rev-RRE activity was more difficult to reverse from latency than the virus with higher Rev-RRE activity. Thus, differences in provirus Rev-RRE activity may be a barrier to developing effective latency reversal strategies. These findings provide new insights into the complex roles the Rev/RRE axis plays in functionality, viral fitness, evolution, and persistence.