Macrophage mitochondrial and stress response to ingestion of Cryptococcus neoformans.

Human infection with Cryptococcus neoformans, a common fungal pathogen, follows deposition of yeast spores in the lung alveoli. The subsequent host-pathogen interaction can result in eradication, latency, or extrapulmonary dissemination. Successful control of C. neoformans infection is dependent on host macrophages, but macrophages display little ability to kill C. neoformans in vitro. Recently, we reported that ingestion of C. neoformans by mouse macrophages induces early cell cycle progression followed by mitotic arrest, an event that almost certainly reflects host cell damage. The goal of the present work was to understand macrophage pathways affected by C. neoformans toxicity. Infection of macrophages by C. neoformans was associated with alterations in protein translation rate and activation of several stress pathways, such as hypoxia-inducing factor-1-α, receptor-interacting protein 1, and apoptosis-inducing factor. Concomitantly we observed mitochondrial depolarization in infected macrophages, an observation that was replicated in vivo. We also observed differences in the stress pathways activated, depending on macrophage cell type, consistent with the nonspecific nature of C. neoformans virulence known to infect phylogenetically distant hosts. Our results indicate that C. neoformans infection impairs multiple host cellular functions and undermines the health of these critical phagocytic cells, which can potentially interfere with their ability to clear this fungal pathogen.

CD14+CD16+ monocyte transmigration across the blood-brain barrier is associated with HIV-NCI despite viral suppression.

HIV-associated neurocognitive impairment (HIV-NCI) affects 15%-50% of people with HIV (PWH), despite viral suppression with antiretroviral therapy (ART). HIV neuropathogenesis is mediated, in part, by transmigration of infected CD14+CD16+ monocytes across the blood-brain barrier (BBB) into the central nervous system (CNS). In the CNS, CD14+CD16+ monocytes contribute to infection and activation of parenchymal cells, resulting in production of neurotoxic viral and host factors that cause neuronal damage. Mechanisms by which CD14+CD16+ monocytes contribute to HIV-NCI have not been characterized in a study population of PWH on ART without contribution from confounders that affect cognition (e.g., substance use, hepatitis C virus coinfection). We assessed cognitive function, PBMC transmigration across the BBB, and neuronal health markers in a well-defined cohort of 56 PWH on ART using stringent criteria to eliminate confounding factors. We demonstrated that PWH on ART with HIV-NCI have significantly increased transmigration of their CD14+CD16+ monocytes across the BBB compared with those with normal cognition. We showed that hypertension and diabetes may be effect modifiers on the association between CD14+CD16+ monocyte transmigration and cognition. This study underscored the persistent role of CD14+CD16+ monocytes in HIV-NCI, even in PWH with viral suppression, suggesting them as potential targets for therapeutic interventions.

Central Nervous System (CNS) Viral Seeding by Mature Monocytes and Potential Therapies To Reduce CNS Viral Reservoirs in the cART Era.

The human immunodeficiency virus (HIV) enters the central nervous system (CNS) within a few days after primary infection, establishing viral reservoirs that persist even with combined antiretroviral therapy (cART). We show that monocytes from people living with HIV (PLWH) on suppressive cART harboring integrated HIV, viral mRNA, and/or viral proteins preferentially transmigrate across the blood-brain barrier (BBB) to CCL2 and are significantly enriched post-transmigration, and even more highly enriched posttransmigration than T cells with similar properties. Using HIV-infected ART-treated mature monocytes cultured in vitro, we recapitulate these findings and demonstrate that HIV+ CD14+ CD16+ ART-treated monocytes also preferentially transmigrate. Cenicriviroc and anti-JAM-A and anti-ALCAM antibodies significantly and preferentially reduce/block transmigration of HIV+ CD14+ CD16+ ART-treated monocytes. These findings highlight the importance of monocytes in CNS HIV reservoirs and suggest targets to eliminate their formation and reseeding.IMPORTANCE We characterized mechanisms of CNS viral reservoir establishment/replenishment using peripheral blood mononuclear cells (PBMC) of PLWH on cART and propose therapeutic targets to reduce/block selective entry of cells harboring HIV (HIV+) into the CNS. Using DNA/RNAscope, we show that CD14+ CD16+ monocytes with integrated HIV, transcriptionally active, and/or with active viral replication from PBMC of PLWH prescribed cART and virally suppressed, selectively transmigrate across a human BBB model. This is the first study to our knowledge demonstrating that monocytes from PLWH with HIV disease for approximately 22 years and with long-term documented suppression can still carry virus into the CNS that has potential to be reactivated and infectious. This selective entry into the CNS-and likely other tissues-indicates a mechanism of reservoir formation/reseeding in the cART era. Using blocking studies, we propose CCR2, JAM-A, and ALCAM as targets on HIV+ CD14+ CD16+ monocytes to reduce and/or prevent CNS reservoir replenishment and to treat HAND and other HIV-associated comorbidities.

Interactions of Monocytes, HIV, and ART Identified by an Innovative scRNAseq Pipeline: Pathways to Reservoirs and HIV-Associated Comorbidities.

HIV reservoirs persist despite successful antiretroviral therapy (ART) and are a major obstacle to the eradication and cure of HIV. The mature monocyte subset, CD14+CD16+, contributes to viral reservoirs and HIV-associated comorbidities. Only a subset of monocytes harbors HIV (HIV+), while the rest remain uninfected, exposed cells (HIVexp). We developed an innovative single cell RNA sequencing (scRNAseq) pipeline that detects HIV and host transcripts simultaneously, enabling us to examine differences between HIV+ and HIVexp mature monocytes. Using this, we characterized uninfected, HIV+, and HIVexp primary human mature monocytes with and without ART. We showed that HIV+ mature monocytes do not form their own cluster separately from HIVexp but can be distinguished by significant differential gene expression. We found that ART decreased levels of unspliced HIV transcripts potentially by modulating host transcriptional regulators shown to decrease viral infection and replication. We also identified and characterized mature monocyte subpopulations differentially impacted by HIV and ART. We identified genes dysregulated by ART in HIVexp monocytes compared to their uninfected counterpart and, of interest, the junctional protein ALCAM, suggesting that ART impacts monocyte functions. Our data provide a novel method for simultaneous detection of HIV and host transcripts. We identify potential targets, such as those genes whose expression is increased in HIV+ mature monocytes compared to HIVexp, to block their entry into tissues, preventing establishment/replenishment of HIV reservoirs even with ART, thereby reducing and/or eliminating viral burden and HIV-associated comorbidities. Our data also highlight the heterogeneity of mature monocyte subsets and their potential contributions to HIV pathogenesis in the ART era.IMPORTANCE HIV enters tissues early after infection, leading to establishment and persistence of HIV reservoirs despite antiretroviral therapy (ART). Viral reservoirs are a major obstacle to the eradication and cure of HIV. CD14+CD16+ (mature) monocytes may contribute to establishment and reseeding of reservoirs. A subset of monocytes, consisting mainly of CD14+CD16+ cells, harbors HIV (HIV+), while the rest remain uninfected, exposed cells (HIVexp). It is important to identify cells harboring virus to eliminate reservoirs. Using an innovative single-cell RNA sequencing (scRNAseq) pipeline to detect HIV and host transcripts simultaneously, we characterized HIV+ and HIVexp primary human mature monocytes with and without ART. HIV+ mature monocytes are not a unique subpopulation but rather can be distinguished from HIVexp by differential gene expression. We characterized mature monocyte subpopulations differently impacted by HIV and ART, highlighting their potential contributions to HIV-associated comorbidities. Our data propose therapeutic targets to block HIV+ monocyte entry into tissues, preventing establishment and replenishment of reservoirs even with ART.

Methamphetamine Increases the Proportion of SIV-Infected Microglia/Macrophages, Alters Metabolic Pathways, and Elevates Cell Death Pathways: A Single-Cell Analysis.

Both substance use disorder and HIV infection continue to affect many individuals. Both have untoward effects on the brain, and the two conditions often co-exist. In the brain, macrophages and microglia are infectable by HIV, and these cells are also targets for the effects of drugs of abuse, such as the psychostimulant methamphetamine. To determine the interaction of HIV and methamphetamine, we isolated microglia and brain macrophages from SIV-infected rhesus monkeys that were treated with or without methamphetamine. Cells were subjected to single-cell RNA sequencing and results were analyzed by statistical and bioinformatic analysis. In the animals treated with methamphetamine, a significantly increased proportion of the microglia and/or macrophages were infected by SIV. In addition, gene encoding functions in cell death pathways were increased, and the brain-derived neurotropic factor pathway was inhibited. The gene expression patterns in infected cells did not cluster separately from uninfected cells, but clusters comprised of microglia and/or macrophages from methamphetamine-treated animals differed in neuroinflammatory and metabolic pathways from those comprised of cells from untreated animals. Methamphetamine increases CNS infection by SIV and has adverse effects on both infected and uninfected microglia and brain macrophages, highlighting the dual and interacting harms of HIV infection and drug abuse on the brain.

CCR2 on Peripheral Blood CD14+CD16+ Monocytes Correlates with Neuronal Damage, HIV-Associated Neurocognitive Disorders, and Peripheral HIV DNA: reseeding of CNS reservoirs?

HIV-associated neurocognitive disorders (HAND) occur in ~50% of HIV infected individuals despite combined antiretroviral therapy. Transmigration into the CNS of CD14+CD16+ monocytes, particularly those that are HIV infected and express increased surface chemokine receptor CCR2, contributes to neuroinflammation and HAND. To examine whether in HIV infected individuals CCR2 on CD14+CD16+ monocytes serves as a potential peripheral blood biomarker of HAND, we examined a cohort of 45 HIV infected people. We correlated CCR2 on CD14+CD16+ monocytes with cognitive status, proton magnetic resonance spectroscopy (1H-MRS) measured neurometabolite levels, and peripheral blood mononuclear cell (PBMC) HIV DNA copies. We determined that CCR2 was increased specifically on CD14+CD16+ monocytes from people with HAND (median [interquartile range (IQR)]) (63.3 [51.6, 79.0]), compared to those who were not cognitively impaired (38.8 [26.7, 56.4]) or those with neuropsychological impairment due to causes other than HIV (39.8 [30.2, 46.5]). CCR2 was associated with neuronal damage, based on the inverse correlation of CCR2 on CD14+CD16+ monocytes with total N-Acetyl Aspartate (tNAA)/total Creatine (tCr) (r2 = 0.348, p = 0.01) and Glutamine-Glutamate (Glx)/tCr (r2 = 0.356, p = 0.01) in the right and left caudate nucleus, respectively. CCR2 on CD14+CD16+ monocytes also correlated with PBMC HIV DNA copies (ρ = 0.618, p = 0.02) that has previously been associated with HAND. These findings suggest that CCR2 on CD14+CD16+ monocytes may be a peripheral blood biomarker of HAND, indicative of increased HIV infected CD14+CD16+ monocyte entry into the CNS that possibly increases the macrophage viral reservoir and contributes to HAND.

Mechanisms of CNS Viral Seeding by HIV+ CD14+ CD16+ Monocytes: Establishment and Reseeding of Viral Reservoirs Contributing to HIV-Associated Neurocognitive Disorders.

HIV reservoirs persist despite antiretroviral therapy (ART) and are established within a few days after infection. Infected myeloid cells in the central nervous system (CNS) may contribute to the establishment of a CNS viral reservoir. The mature CD14+ CD16+ monocyte subset enters the CNS in response to chemokines, including CCL2. Entry of infected CD14+ CD16+ monocytes may lead to infection of other CNS cells, including macrophages or microglia and astrocytes, and to release of neurotoxic early viral proteins and additional cytokines. This contributes to neuroinflammation and neuronal damage leading to HIV-associated neurocognitive disorders (HAND) in ~50% of HIV-infected individuals despite ART. We examined the mechanisms of monocyte entry in the context of HIV infection and report for the first time that HIV+ CD14+ CD16+ monocytes preferentially transmigrate across the blood-brain barrier (BBB). The junctional proteins JAM-A and ALCAM and the chemokine receptor CCR2 are essential to their preferential transmigration across the BBB to CCL2. We show here that JAM-A and ALCAM are increased on HIV+ CD14+ CD16+ monocytes compared to their expression on HIVexp CD14+ CD16+ monocytes-cells that are uninfected but exposed to HIV, viral proteins, and inflammatory mediators. Antibodies against JAM-A and ALCAM and the novel CCR2/CCR5 dual inhibitor cenicriviroc prevented or significantly reduced preferential transmigration of HIV+ CD14+ CD16+ monocytes. This indicates that JAM-A, ALCAM, and CCR2 may be potential therapeutic targets to block entry of these infected cells into the brain and prevent or reduce the establishment and replenishment of viral reservoirs within the CNS.IMPORTANCE HIV infects different tissue compartments of the body, including the central nervous system (CNS). This leads to establishment of viral reservoirs within the CNS that mediate neuroinflammation and neuronal damage, contributing to cognitive impairment. Our goal was to examine the mechanisms of transmigration of cells that contribute to HIV infection of the CNS and to continued replenishment of CNS viral reservoirs, to establish potential therapeutic targets. We found that an HIV-infected subset of monocytes, mature HIV+ CD14+ CD16+ monocytes, preferentially transmigrates across the blood-brain barrier. This was mediated, in part, by increased junctional proteins JAM-A and ALCAM and chemokine receptor CCR2. We show that the CCR2/CCR5 dual inhibitor cenicriviroc and blocking antibodies against the junctional proteins significantly reduce, and often completely block, the transmigration of HIV+ CD14+ CD16+ monocytes. This suggests new opportunities to eliminate infection and seeding or reseeding of viral reservoirs within the CNS, thus reducing neuroinflammation, neuronal damage, and cognitive impairment.

The α7-nicotinic receptor is upregulated in immune cells from HIV-seropositive women: consequences to the cholinergic anti-inflammatory response.

Antiretroviral therapy partially restores the immune system and markedly increases life expectancy of HIV-infected patients. However, antiretroviral therapy does not restore full health. These patients suffer from poorly understood chronic inflammation that causes a number of AIDS and non-AIDS complications. Here we show that chronic inflammation in HIV+ patients may be due to the disruption of the cholinergic anti-inflammatory pathway by HIV envelope protein gp120IIIB. Our results demonstrate that HIV gp120IIIB induces α7 nicotinic acetylcholine receptor (α7) upregulation and a paradoxical proinflammatory phenotype in macrophages, as activation of the upregulated α7 is no longer capable of inhibiting the release of proinflammatory cytokines. Our results demonstrate that disruption of the cholinergic-mediated anti-inflammatory response can result from an HIV protein. Collectively, these findings suggest that HIV tampering with a natural strategy to control inflammation could contribute to a crucial, unresolved problem of HIV infection: chronic inflammation.