Increased monocyte turnover from bone marrow correlates with severity of SIV encephalitis and CD163 levels in plasma

Elevated PCNA+ tumor-associated macrophages in breast cancer are associated with early recurrence and non-Caucasian ethnicity

African American and Hispanic women develop more triple negative breast cancer at younger ages than Caucasian women. The frequently observed association between race and socioeconomic status (SES) has confounded our understanding of the outcomes disparities seen in these groups. Given the association between inflammatory cells and high-grade, triple negative tumors, we sought to investigate whether differences in the presence of these cells varies by race. We evaluated breast tumor specimens for the presence PCNA+ tumor-associated macrophages (TAMs) in consecutive cases from a county hospital serving primarily un- or under-insured patients. All patients in this cohort had elevated PCNA + TAM levels. Higher PCNA + TAM counts were associated with hormone receptor (HR) negative tumors and non-Caucasian ethnicity. Hispanic women specifically had significantly higher PCNA + TAM counts than Caucasian patients and shorter disease-free survival. These findings implicate immune function in the development of aggressive breast cancer and suggest a possible link between SES and the inflammatory response.

Keratinocyte expression of calcitonin gene-related peptide β: implications for neuropathic and inflammatory pain mechanisms

Calcitonin gene-related peptide (CGRP) is a vasodilatory peptide that has been detected at high levels in the skin, blood, and cerebrospinal fluid (CSF) under a variety of inflammatory and chronic pain conditions, presumably derived from peptidergic C and Aδ innervation. Herein, CGRP immunolabeling (IL) was detected in epidermal keratinocytes at levels that were especially high and widespread in the skin of humans from locations afflicted with postherpetic neuralgia (PHN) and complex region pain syndrome type 1 (CRPS), of monkeys infected with simian immunodeficiency virus, and of rats subjected to L5/L6 spinal nerve ligation, sciatic nerve chronic constriction, and subcutaneous injection of complete Freund's adjuvant. Increased CGRP-IL was also detected in epidermal keratinocytes of transgenic mice with keratin-14 promoter driven overexpression of noggin, an antagonist to BMP-4 signaling. Transcriptome microarray, quantitative Polymerase Chain Reaction (qPCR), and Western blot analyses using laser-captured mouse epidermis from transgenics, monolayer cultures of human and mouse keratinocytes, and multilayer human keratinocyte organotypic cultures, revealed that keratinocytes express predominantly the beta isoform of CGRP. Cutaneous peptidergic innervation has been shown to express predominantly the alpha isoform of CGRP. Keratinocytes also express the cognate CGRP receptor components, Calcitonin receptor-like receptor (CRLR), Receptor activity-modifying protein 1 (RAMP1), CGRP-receptor component protein (RCP) consistent with known observations that CGRP promotes several functional changes in keratinocytes, including proliferation and cytokine production. Our results indicate that keratinocyte-derived CGRPβ may modulate epidermal homeostasis through autocrine/paracrine signaling and may contribute to chronic pain under pathological conditions.

Pathogenesis of HIV in the central nervous system

HIV can infect the brain and impair central nervous system (CNS) function. Combination antiretroviral therapy (cART) has not eradicated CNS complications. HIV-associated neurocognitive disorders (HAND) remain common despite cART, although attenuated in severity. This may result from a combination of factors including inadequate treatment of HIV reservoirs such as circulating monocytes and glia, decreased effectiveness of cART in CNS, concurrent illnesses, stimulant use, and factors associated with prescribed drugs, including antiretrovirals. This review highlights recent investigations of HIV-related CNS injury with emphasis on cART-era neuropathological mechanisms in the context of both US and international settings.

Differential expression of CD163 on monocyte subsets in healthy and HIV-1 infected individuals

CD163, a haptoglobin-hemoglobin (Hp-Hb) scavenger receptor, expressed by monocytes and macrophages, is important in resolution of inflammation. Age-related non-AIDS co-morbidities in HIV-infected individuals, particularly dementia and cardiovascular disease, result in part from effects of HIV-1 infection on monocyte and macrophage biology. CD163 co-expression on CD14+CD16++ monocytes has been proposed as a useful biomarker for HIV-1 disease progression and the presence of HIV associated dementia. Here we investigated CD163 expression on monocyte subsets ex vivo, on cultured macrophages, and soluble in plasma, in the setting of HIV-1 infection. Whole blood immunophenotyping revealed CD163 expression on CD14++CD16- monocytes but not on CD14+CD16++ monocytes (P = 0.004), supported by CD163 mRNA levels. Incubation with M-CSF induced CD163 protein expression on CD14+CD16++ monocytes to the same extent as CD14++CD16− monocytes. CD163 expression on CD14++CD16+ monocytes from HIV-infected subjects was significantly higher than from uninfected individuals, with a trend towards increased expression on CD14++CD16− monocytes (P = 0.019 and 0.069 respectively), which is accounted for by HIV-1 therapy including protease inhibitors. Shedding of CD163 was shown to predominantly occur from the CD14++CD16− subset after Ficoll isolation and LPS stimulation. Soluble CD163 concentration in plasma from HIV-1 infected donors was similar to HIV-1 uninfected donors. Monocyte CD163 expression in HIV-1 infected patients showed a complicated relationship with classical measures of disease progression. Our findings clarify technical issues regarding CD163 expression on monocyte subsets and further elucidates its role in HIV-associated inflammation by demonstrating that CD163 is readily lost from CD14++CD16− monocytes and induced in pro-inflammatory CD14+CD16++ monocytes by M-CSF. Our data show that all monocyte subsets are potentially capable of differentiating into CD163-expressing anti-inflammatory macrophages given appropriate stimuli. Levels of CD163 expression on monocytes may be a potential biomarker reflecting efforts by the immune system to resolve immune activation and inflammation in HIV-infected individuals.

Breaking down the barrier: the effects of HIV-1 on the blood-brain barrier

Human immunodeficiency virus type 1 (HIV-1) primarily infects CD4(+) T cells and cells of the monocyte-macrophage lineage, resulting in immunodeficiency in an infected patient. Along with this immune deficiency, HIV-1 has been linked to a number of neurological symptoms in the absence of opportunistic infections or other co-morbidities, suggesting that HIV-1 is able to cross the blood-brain barrier (BBB), enter the central nervous system (CNS), and cause neurocognitive impairment. HIV-1-infected monocyte-macrophages traverse the BBB and enter the CNS throughout the course of HIV-1 disease. Once in the brain, both free virus and virus-infected cells are able to infect neighboring resident microglia and astrocytes and possibly other cell types. HIV-1-infected cells in both the periphery and the CNS give rise to elevated levels of viral proteins, including gp120, Tat, and Nef, and of host inflammatory mediators such as cytokines and chemokines. It has been shown that the viral proteins may act alone or in concert with host cytokines and chemokines, affecting the integrity of the BBB. The pathological end point of these interactions may facilitate a positive feedback loop resulting in increased penetration of HIV into the CNS. It is proposed in this review that the dysregulation of the BBB during and after neuroinvasion is a critical component of the neuropathogenic process and that dysregulation of this protective barrier is caused by a combination of viral and host factors including secreted viral proteins, components of the inflammatory process, the aging process, therapeutics, and drug or alcohol abuse.

Minocycline inhibition of monocyte activation correlates with neuronal protection in SIV neuroAIDS

Background

Minocycline is a tetracycline antibiotic that has been proposed as a potential conjunctive therapy for HIV-1 associated cognitive disorders. Precise mechanism(s) of minocycline's functions are not well defined.

Methods

Fourteen rhesus macaques were SIV infected and neuronal metabolites measured by proton magnetic resonance spectroscopy (¹H MRS). Seven received minocycline (4 mg/kg) daily starting at day 28 post-infection (pi). Monocyte expansion and activation were assessed by flow cytometry, cell traffic to lymph nodes, CD16 regulation, viral replication, and cytokine production were studied.

Results

Minocycline treatment decreased plasma virus and pro-inflammatory CD14+CD16+ and CD14^loCD16+ monocytes, and reduced their expression of CD11b, CD163, CD64, CCR2 and HLA-DR. There was reduced recruitment of monocyte/macrophages and productively infected cells in axillary lymph nodes. There was an inverse correlation between brain NAA/Cr (neuronal injury) and circulating CD14+CD16+ and CD14^loCD16+ monocytes. Minocycline treatment in vitro reduced SIV replication CD16 expression on activated CD14+CD16+ monocytes, and IL-6 production by monocytes following LPS stimulation.

Conclusion

Neuroprotective effects of minocycline are due in part to reduction of activated monocytes, monocyte traffic. Mechanisms for these effects include CD16 regulation, reduced viral replication, and inhibited immune activation.

HIV reservoirs and latency models

The main impediment to a cure for HIV is the existence of long-lasting treatment resistant viral reservoirs. In this review, we discuss what is currently known about reservoirs, including their formation and maintenance, while focusing on latently infected CD4+ T cells. In addition, we compare several different in vivo and in vitro models of latency. We comment on how each model may reflect the properties of reservoirs in vivo, especially with regard to cell phenotype, since recent studies demonstrate that multiple CD4+ T cell subsets contribute to HIV reservoirs and that with HAART and disease progression the relative contribution of different subsets may change. Finally, we focus on the direct infection of resting CD4+ T cells as a source of reservoir formation and as a model of latency, since recent results help explain the misconception that resting CD4+ T cells appeared to be resistant to HIV in vitro.

Early myeloid dendritic cell dysregulation is predictive of disease progression in simian immunodeficiency virus infection

Myeloid dendritic cells (mDC) are lost from blood in individuals with human immunodeficiency virus (HIV) infection but the mechanism for this loss and its relationship to disease progression are not known. We studied the mDC response in blood and lymph nodes of simian immunodeficiency virus (SIV)-infected rhesus macaques with different disease outcomes. Early changes in blood mDC number were inversely correlated with virus load and reflective of eventual disease outcome, as animals with stable infection that remained disease-free for more than one year had average increases in blood mDC of 200% over preinfection levels at virus set-point, whereas animals that progressed rapidly to AIDS had significant loss of mDC at this time. Short term antiretroviral therapy (ART) transiently reversed mDC loss in progressor animals, whereas discontinuation of ART resulted in a 3.5-fold increase in mDC over preinfection levels only in stable animals, approaching 10-fold in some cases. Progressive SIV infection was associated with increased CCR7 expression on blood mDC and an 8-fold increase in expression of CCL19 mRNA in lymph nodes, consistent with increased mDC recruitment. Paradoxically, lymph node mDC did not accumulate in progressive infection but rather died from caspase-8-dependent apoptosis that was reduced by ART, indicating that increased recruitment is offset by increased death. Lymph node mDC from both stable and progressor animals remained responsive to exogenous stimulation with a TLR7/8 agonist. These data suggest that mDC are mobilized in SIV infection but that an increase in the CCR7-CCL19 chemokine axis associated with high virus burden in progressive infection promotes exodus of activated mDC from blood into lymph nodes where they die from apoptosis. We suggest that inflamed lymph nodes serve as a sink for mDC through recruitment, activation and death that contributes to AIDS pathogenesis.

Myeloid dendritic cells (mDC) are essential innate immune system cells that are lost from blood in human immunodeficiency virus infection through an ill-defined mechanism. We studied the kinetics of the mDC response in blood and lymph nodes of rhesus macaques infected with the closely related simian immunodeficiency virus. We found that differences in the number of blood mDC correlated with eventual disease outcome, as at virus set-point mDC were increased in blood in animals remaining disease free but lost from blood in animals that progressed rapidly to AIDS. mDC loss was linked to an increase in the chemokine axis responsible for mDC recruitment to lymph nodes; however, mDC did not accumulate in tissues but rather died from apoptosis. Lymph node mDC remained responsive to stimulation with a TLR7/8 agonist during infection. Importantly, mDC dysregulation was partially reversed by antiretroviral therapy. These data indicate that chronic mDC recruitment, activation and death within lymph nodes precede development of disease in SIV infected monkeys and may play a role in AIDS pathogenesis.

Immunophenotyping of lymphocyte, monocyte and dendritic cell subsets in normal rhesus macaques by 12-color flow cytometry: clarification on DC heterogeneity

Monitoring changes in rhesus macaque immune cell populations during infectious disease is crucial. The aim of this work was to simultaneously analyze the phenotype of rhesus macaque lymphocyte, monocyte and dendritic cell (DC) subsets using a single 12-color flow cytometry panel. Blood from healthy non-infected rhesus macaques was labeled with a cocktail of 12 antibodies. Data were compared to three smaller lineage specific panels and absolute and relative percentages of cells were compared. Our 12-color panel allows for the identification of the following major subsets: CD4+ and CD8+ T lymphocytes, B lymphocytes, natural killer (NK) cells, natural killer T (NKT) cells, monocyte subsets and four non-overlapping Lin-HLA-DR+ cell subsets: CD34+ hematopoietic stem cells, CD11c- CD123+ plasmacytoid DC, CD11c+ CD16+ and CD11c(-)(/dim) CD1c+ myeloid DC. The development of a multiparameter flow cytometry panel will allow for simultaneous enumeration of mature lymphocyte, NK cells, monocyte and DC subsets. Studying these major players of the immune system in one panel may give us a broader view of the immune response during SIV infection and the ability to better define the role of each of these individual cell types in the pathogenesis of AIDS.