Monocytes and cells of the dendritic cell lineage circulate in blood and eventually migrate into tissue where they further mature and serve various functions, most notably in immune defense. Over ...recent years these cells have been characterized in detail with the use of cell surface markers and flow cytometry, and subpopulations have been described. The present document proposes a nomenclature for these cells and defines 3 types of monocytes (classical, intermediate, and nonclassical monocytes) and 3 types of dendritic cells (plasmacytoid and 2 types of myeloid dendritic cells) in human and in mouse blood. This classification has been approved by the Nomenclature Committee of the International Union of Immunological Societies, and we are convinced that it will facilitate communication among experts and in the wider scientific community.
The chemokine receptors CCR5 and CXCR4 are “front doors” for HIV-1 infection in host cells, and their targeting represents a potential solution for a cure. Dudek et al.1 now propose a new gene ...editing strategy to simultaneously block CCR5- and CXCR4-mediated HIV-1 entry in autologous hematopoietic stem and progenitor cells (HSPCs).
The chemokine receptors CCR5 and CXCR4 are “front doors” for HIV-1 infection in host cells, and their targeting represents a potential solution for a cure. Dudek et al.1 now propose a new gene editing strategy to simultaneously block CCR5- and CXCR4-mediated HIV-1 entry in autologous hematopoietic stem and progenitor cells (HSPCs).
Nearly 2.3 million individuals worldwide are coinfected with human immunodeficiency virus (HIV) and hepatitis C virus (HCV). Odds of HCV infection are six times higher in people living with HIV ...(PLWH) compared to their HIV-negative counterparts, with the highest prevalence among people who inject drugs (PWID) and men who have sex with men (MSM). HIV coinfection has a detrimental impact on the natural history of HCV, including higher rates of HCV persistence following acute infection, higher viral loads, and accelerated progression of liver fibrosis and development of end-stage liver disease compared to HCV monoinfection. Similarly, it has been reported that HCV coinfection impacts HIV disease progression in PLWH receiving anti-retroviral therapies (ART) where HCV coinfection negatively affects the homeostasis of CD4
T cell counts and facilitates HIV replication and viral reservoir persistence. While ART does not cure HIV, direct acting antivirals (DAA) can now achieve HCV cure in nearly 95% of coinfected individuals. However, little is known about how HCV cure and the subsequent resolution of liver inflammation influence systemic immune activation, immune reconstitution and the latent HIV reservoir. In this review, we will summarize the current knowledge regarding the pathogenesis of HIV/HCV coinfection, the effects of HCV coinfection on HIV disease progression in the context of ART, the impact of HIV on HCV-associated liver morbidity, and the consequences of DAA-mediated HCV cure on immune reconstitution and HIV reservoir persistence in coinfected patients.
The CD16+ subset of peripheral blood monocytes (Mo) is expanded dramatically during inflammatory conditions including sepsis, HIV‐1 infection, and cancer. CD16+ express high levels of CX3CR1, which ...mediates arrest onto CX3CL1‐expressing endothelial cells (EC) under flow conditions. In contrast, attachment of CD16− Mo onto cytokine‐activated EC is independent of CX3CL1. Here, we investigate the ability of CD16+ and CD16− Mo to produce proinflammatory cytokines upon interaction with CX3CL1‐expressing HUVEC. We demonstrate that CD16+ but not CD16− Mo produce high levels of IL‐6, CCL2, and matrix metalloproteinase (MMP)‐9 when cocultured with TNF/IFN‐γ‐activated HUVEC or nonactivated HUVEC expressing CX3CL1. Furthermore, supernatants from Mo cocultured with cytokine‐activated HUVEC induce neuronal death in vitro. These results suggest that membrane‐bound CX3CL1 stimulates production of IL‐6, CCL2, and MMP‐9 by CD16+ Mo, likely via engagement of CX3CR1. Thus, expansion of CD16+ Mo and their accumulation onto CX3CL1‐expressing EC may result in recruitment of Mo and T cell subsets at sites of inflammation in response to CCL2, IL‐6‐induced cell activation and/or differentiation, and MMP‐9‐mediated vascular and tissue injury.
Immune activation is a strong predictor of disease progression in HIV infection. Combinatorial plasma biomarker signatures that represent surrogate markers of immune activation in both viremic and ...aviremic HIV patients on combination antiretroviral therapy (cART) have not been defined. Here, we identify a plasma inflammatory biomarker signature that distinguishes between both viremic and aviremic HIV patients on cART and healthy controls and examine relationships of this signature to markers of disease progression.
Multiplex profiling and ELISA were used to detect 15 cytokines/chemokines, soluble IL-2R (sIL-2R), and soluble CD14 (sCD14) in plasma from 57 HIV patients with CD4 nadir <300 cells/µl and 29 healthy controls. Supervised and unsupervised analyses were used to identify biomarkers explaining variance between groups defined by HIV status or drug abuse. Relationships between biomarkers and disease markers were examined by Spearman correlation.
The majority (91%) of HIV subjects were on cART, with 38% having undetectable viral loads (VL). Hierarchical clustering identified a biomarker cluster in plasma consisting of two interferon-stimulated gene products (CXCL9 and CXCL10), T cell activation marker (sIL-2R), and monocyte activation marker (sCD14) that distinguished both viremic and aviremic HIV patients on cART from controls (p<0.0001) and were top-ranked in variables important in projection plots. IL-12 and CCL4 were also elevated in viremic and aviremic patients compared to controls (p<0.05). IL-12 correlated with IFNα, IFNγ, CXCL9, and sIL-2R (p<0.05). CXCL10 correlated positively with plasma VL and percentage of CD16+ monocytes, and inversely with CD4 count (p = 0.001, <0.0001, and 0.04, respectively).
A plasma inflammatory biomarker signature consisting of CXCL9, CXCL10, sIL-2R, and sCD14 may be useful as a surrogate marker to monitor immune activation in both viremic and aviremic HIV patients on cART during disease progression and therapeutic responses.
Background. Tryptophan (Trp) catabolism into kynurenine (Kyn) contributes to immune dysfunction in chronic human immunodeficiency virus (HIV) infection. To better define the relationship between Trp ...catabolism, inflammation, gut mucosal dysfunction, and the role of early antiretroviral therapy (ART), we prospectively assessed patients early after they acquired HIV. Methods. Forty patients in the early phase of infection were longitudinally followed for 12 months after receiving a diagnosis of HIV infection; 24 were untreated, and 16 were receiving ART. Kyn/Trp ratio, regulatory T-cells (Tregs) frequency, T-cell activation, dendritic cell counts, and plasma levels of gut mucosal dysfunction markers intestinal-type fatty acid-binding protein, soluble suppression of tumorigenicity 2, and lipopolysaccharide were assessed. Results. Compared with healthy subjects, patients in the early phase of infection presented with elevated Kyn/Trp ratios, which further increased in untreated patients but normalized in ART recipients. Accordingly, in untreated subjects, the elevated Treg frequency observed at baseline continued to increase over time. The highest CD8 + T-cell activation was observed during the early phase of infection and decreased in untreated patients, whereas activation normalized in ART recipients. The Kyn/Trp ratio was positively associated with CD8⁺ T-cell activation and levels of inflammatory cytokines (interleukin 6, interferon γ-inducible protein 10, interleukin 18, and tumor necrosis factor a) and negatively associated with dendritic cell frequencies at baseline and in untreated patients. However, ART did not normalize plasma levels of gut mucosal dysfunction markers. Conclusions. Early initiation of ART normalized enhanced Trp catabolism and immune activation but did not improve plasma levels of gut mucosal dysfunction markers.
Elevated plasma lipopolysaccharide (LPS), an indicator of microbial translocation from the gut, is a likely cause of systemic immune activation in chronic HIV infection. LPS induces monocyte ...activation and trafficking into brain, which are key mechanisms in the pathogenesis of HIV-associated dementia (HAD). To determine whether high LPS levels are associated with increased monocyte activation and HAD, we obtained peripheral blood samples from AIDS patients and examined plasma LPS by Limulus amebocyte lysate (LAL) assay, peripheral blood monocytes by FACS, and soluble markers of monocyte activation by ELISA. Purified monocytes were isolated by FACS sorting, and HIV DNA and RNA levels were quantified by real time PCR. Circulating monocytes expressed high levels of the activation markers CD69 and HLA-DR, and harbored low levels of HIV compared to CD4(+) T-cells. High plasma LPS levels were associated with increased plasma sCD14 and LPS-binding protein (LBP) levels, and low endotoxin core antibody levels. LPS levels were higher in HAD patients compared to control groups, and were associated with HAD independently of plasma viral load and CD4 counts. LPS levels were higher in AIDS patients using intravenous heroin and/or ethanol, or with Hepatitis C virus (HCV) co-infection, compared to control groups. These results suggest a role for elevated LPS levels in driving monocyte activation in AIDS, thereby contributing to the pathogenesis of HAD, and provide evidence that cofactors linked to substance abuse and HCV co-infection influence these processes.
Human peripheral blood monocytes (Mo) consist of subsets distinguished by expression of CD16 (FCgammaRIII) and chemokine receptors. Classical CD16- Mo express CCR2 and migrate in response to CCL2, ...while a minor CD16+ Mo subset expresses CD16 and CX3CR1 and migrates into tissues expressing CX3CL1. CD16+ Mo produce pro-inflammatory cytokines and are expanded in certain inflammatory conditions including sepsis and HIV infection.
To gain insight into the developmental relationship and functions of CD16+ and CD16- Mo, we examined transcriptional profiles of these Mo subsets in peripheral blood from healthy individuals. Of 16,328 expressed genes, 2,759 genes were differentially expressed and 228 and 250 were >2-fold upregulated and downregulated, respectively, in CD16+ compared to CD16- Mo. CD16+ Mo were distinguished by upregulation of transcripts for dendritic cell (DC) (SIGLEC10, CD43, RARA) and macrophage (MPhi) (CSF1R/CD115, MafB, CD97, C3aR) markers together with transcripts relevant for DC-T cell interaction (CXCL16, ICAM-2, LFA-1), cell activation (LTB, TNFRSF8, LST1, IFITM1-3, HMOX1, SOD-1, WARS, MGLL), and negative regulation of the cell cycle (CDKN1C, MTSS1), whereas CD16- Mo were distinguished by upregulation of transcripts for myeloid (CD14, MNDA, TREM1, CD1d, C1qR/CD93) and granulocyte markers (FPR1, GCSFR/CD114, S100A8-9/12). Differential expression of CSF1R, CSF3R, C1QR1, C3AR1, CD1d, CD43, CXCL16, and CX3CR1 was confirmed by flow cytometry. Furthermore, increased expression of RARA and KLF2 transcripts in CD16+ Mo coincided with absence of cell surface cutaneous lymphocyte associated antigen (CLA) expression, indicating potential imprinting for non-skin homing.
These results suggest that CD16+ and CD16- Mo originate from a common myeloid precursor, with CD16+ Mo having a more MPhi - and DC-like transcription program suggesting a more advanced stage of differentiation. Distinct transcriptional programs, together with their recruitment into tissues via different mechanisms, also suggest that CD16+ and CD16- Mo give rise to functionally distinct DC and MPhi in vivo.
Tryptophan (Trp) catabolism into immunosuppressive kynurenine (Kyn) by indoleamine 2,3-dioxygenase (IDO) was previously linked to Th17/Treg differentiation and immune activation. Here we examined Trp ...catabolism and its impact on Th17/Treg balance in uninfected healthy subjects (HS) and a large cohort of HIV-infected patients with different clinical outcomes: ART-naïve, Successfully Treated (ST), and elite controllers (EC). In ART-naïve patients, increased IDO activity/expression, together with elevated levels of TNF-α and sCD40L, were associated with Treg expansion and an altered Th17/Treg balance. These alterations were normalized under ART. In contrast, Trp 2,3-dioxegenase (TDO) expression was dramatically lower in EC when compared to all other groups. Interestingly, EC displayed a distinctive Trp metabolism characterized by low Trp plasma levels similar to ART-naïve patients without accumulating immunosuppressive Kyn levels which was accompanied by a preserved Th17/Treg balance. These results suggest a distinctive Trp catabolism and Th17/Treg balance in HIV progressors and EC. Thus, IDO-induced immune-metabolism may be considered as a new inflammation-related marker for HIV-1 disease progression.
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