Suppression of HIV replication in human monocyte-derived macrophages induced by granulocyte/macrophage colony-stimulating factor

An Evaluation on the Role of Non-Coding RNA in HIV Transcription and Latency: A Review

The existence of latent cellular reservoirs is recognized as the major barrier to an HIV cure. Reactivating and eliminating "shock and kill" or permanently silencing "block and lock" the latent HIV reservoir, as well as gene editing, remain promising approaches, but so far have proven to be only partially successful. Moreover, using latency reversing agents or "block and lock" drugs pose additional considerations, including the ability to cause cellular toxicity, a potential lack of specificity for HIV, or low potency when each agent is used alone. RNA molecules, such as microRNAs (miRNAs) and long non-coding RNAs (lncRNAs) are becoming increasingly recognized as important regulators of gene expression. RNA-based approaches for combatting HIV latency represent a promising strategy since both miRNAs and lncRNAs are more cell-type and tissue specific than protein coding genes. Thus, a higher specificity of targeting the latent HIV reservoir with less overall cellular toxicity can likely be achieved. In this review, we summarize current knowledge about HIV gene expression regulation by miRNAs and lncRNAs encoded in the human genome, as well as regulatory molecules encoded in the HIV genome. We discuss both the transcriptional and post-transcriptional regulation of HIV gene expression to align with the current definition of latency, and describe RNA molecules that either promote HIV latency or have anti-latency properties. Finally, we provide perspectives on using each class of RNAs as potential targets for combatting HIV latency, and describe the complexity of the interactions between different RNA molecules, their protein targets, and HIV.

Micro RNA Targets in HIV Latency: Insights into Novel Layers of Latency Control

Despite the considerable progress that has been made in identifying cellular factors and pathways that contribute to establishment and maintenance of the latent HIV reservoir, it remains the major obstacle to eradicating this virus. Most recently, noncoding genes have been implicated in regulation of HIV expression. In this study, small RNA sequencing was used to profile expression of microRNAs (miRNAs) in a primary CD4+ T cell in vitro model of HIV latency. Previously, we have shown that protein-coding genes dysregulated in this model were enriched for the p53 signaling pathway, which was confirmed experimentally. We further found a link between p53 signaling and dysregulated long noncoding RNAs. In this study, we hypothesized that miRNAs may provide an additional level of regulation of the p53 signaling pathway during HIV latency. Twenty-six miRNAs were identified to be dysregulated in our latency model. A subset of these miRNAs was validated by real-time quantitative polymerase chain reaction. Predicted messenger RNA (mRNA) targets and cellular pathways enriched for mRNA targets were identified using several analytical methods. Our analyses showed that many protein-coding genes and pathways targeted by dysregulated miRNAs have relevance to regulation of HIV expression or establishment of HIV latency. The p53 signaling pathway was found among pathways that were targeted by dysregulated miRNAs at a greater level than expected by chance. This study provides a mechanistic insight into regulation of the p53 pathway through miRNAs that may contribute to the establishment of latency.

Granulocyte macrophage colony-stimulating factor has come of age: From a vaccine adjuvant to antiviral immunotherapy

GM-CSF acts as a pro-inflammatory cytokine and a key growth factor produced by several immune cells such as macrophages and activated T cells. In this review, we discuss recent studies that point to the crucial role of GM-CSF in the immune response against infections. Upon induction, GM-CSF activates four main signalling networks including the JAK/STAT, PI3K, MAPK, and NFκB pathways. Many of these transduction pathways such as JAK/STAT signal via proteins commonly activated with other antiviral signalling cascades, such as those induced by IFNs. GM-CSF also helps defend against respiratory infections by regulating alveolar macrophage differentiation and enhancing innate immunity in the lungs. Here, we also summarize the numerous clinical trials that have taken advantage of GM-CSF's mechanistic attributes in immunotherapy. Moreover, we discuss how GM-CSF is used as an adjuvant in vaccines and how its activity is interfered with to reduce inflammation such as in the case of COVID-19. This review brings forth the current knowledge on the antiviral actions of GM-CSF, the associated signalling cascades, and its application in immunotherapy.

Coxsackievirus B4 Can Infect Human Peripheral Blood-Derived Macrophages

Beyond acute infections, group B coxsackieviruses (CVB) are also reported to play a role in the development of chronic diseases, like type 1 diabetes. The viral pathogenesis mainly relies on the interplay between the viruses and innate immune response in genetically-susceptible individuals. We investigated the interaction between CVB4 and macrophages considered as major players in immune response. Monocyte-derived macrophages (MDM) generated with either M-CSF or GM-CSF were inoculated with CVB4, and infection, inflammation, viral replication and persistence were assessed. M-CSF-induced MDM, but not GM-CSF-induced MDM, can be infected by CVB4. In addition, enhancing serum was not needed to infect MDM in contrast with parental monocytes. The expression of viral receptor (CAR) mRNA was similar in both M-CSF and GM-CSF MDM. CVB4 induced high levels of pro-inflammatory cytokines (IL-6 and TNFα) in both MDM populations. CVB4 effectively replicated and persisted in M-CSF MDM, but IFNα was produced in the early phase of infection only. Our results demonstrate that CVB4 can replicate and persist in MDM. Further investigations are required to determine whether the interaction between the virus and MDM plays a role in the pathogenesis of CVB-induced chronic diseases.

Differential expression of the fractalkine chemokine receptor (CX3CR1) in human monocytes during differentiation

Circulating monocytes (Mos) may continuously repopulate macrophage (MAC) or dendritic cell (DC) populations to maintain homeostasis. MACs and DCs are specialized cells that play different and complementary immunological functions. Accordingly, they present distinct migratory properties. Specifically, whereas MACs largely remain in tissues, DCs are capable of migrating from peripheral tissues to lymphoid organs. The aim of this work was to analyze the expression of the fractalkine receptor (CX3CR1) during the monocytic differentiation process. Freshly isolated Mos express high levels of both CX3CR1 mRNA and protein. During the Mo differentiation process, CX3CR1 is downregulated in both DCs and MACs. However, MACs showed significantly higher CX3CR1 expression levels than did DC. We also observed an antagonistic CX3CR1 regulation by interferon (IFN)-γ and interleukin (IL)-4 during MAC activation through the classical and alternative MAC pathways, respectively. IFN-γ inhibited the loss of CX3CR1, but IL-4 induced it. Additionally, we demonstrated an association between CX3CR1 expression and apoptosis prevention by soluble fractalkine (sCX3CL1) in Mos, DCs and MACs. This is the first report demonstrating sequential and differential CX3CR1 modulation during Mo differentiation. Most importantly, we demonstrated a functional link between CX3CR1 expression and cell survival in the presence of sCX3CL1.

Moderate restriction of macrophage-tropic human immunodeficiency virus type 1 by SAMHD1 in monocyte-derived macrophages

Macrophage-tropic human immunodeficiency virus type 1 (HIV-1) strains are able to grow to high titers in human monocyte-derived macrophages. However, it was recently reported that cellular protein SAMHD1 restricts HIV-1 replication in human cells of the myeloid lineage, including monocyte-derived macrophages. Here we show that degradation of SAMHD1 in monocyte-derived macrophages was associated with moderately enhanced growth of the macrophage-tropic HIV-1 strain. SAMHD1 degradation was induced by treating target macrophages with vesicular stomatitis virus glycoprotein-pseudotyped human immunodeficiency virus type 2 (HIV-2) particles containing viral protein X. For undifferentiated monocytes, HIV-2 particle treatment allowed undifferentiated monocytes to be fully permissive for productive infection by the macrophage-tropic HIV-1 strain. In contrast, untreated monocytes were totally resistant to HIV-1 replication. These results indicated that SAMHD1 moderately restricts even a macrophage-tropic HIV-1 strain in monocyte-derived macrophages, whereas the protein potently restricts HIV-1 replication in undifferentiated monocytes.

Leishmania induces survival, proliferation and elevated cellular dNTP levels in human monocytes promoting acceleration of HIV co-infection

Leishmaniasis is a parasitic disease that is widely prevalent in many tropical and sub-tropical regions of the world. Infection with Leishmania has been recognized to induce a striking acceleration of Human Immunodeficiency Virus Type 1 (HIV-1) infection in coinfected individuals through as yet incompletely understood mechanisms. Cells of the monocyte/macrophage lineage are the predominant cell types coinfected by both pathogens. Monocytes and macrophages contain extremely low levels of deoxynucleoside triphosphates (dNTPs) due to their lack of cell cycling and S phase, where dNTP biosynthesis is specifically activated. Lentiviruses, such as HIV-1, are unique among retroviruses in their ability to replicate in these non-dividing cells due, at least in part, to their highly efficient reverse transcriptase (RT). Nonetheless, viral replication progresses more efficiently in the setting of higher intracellular dNTP concentrations related to enhanced enzyme kinetics of the viral RT. In the present study, in vitro infection of CD14+ peripheral blood-derived human monocytes with Leishmania major was found to induce differentiation, marked elevation of cellular p53R2 ribonucleotide reductase subunit and R2 subunit expression. The R2 subunit is restricted to the S phase of the cell cycle. Our dNTP assay demonstrated significant elevation of intracellular monocyte-derived macrophages (MDMs) dNTP concentrations in Leishmania-infected cell populations as compared to control cells. Infection of Leishmania-maturated MDMs with a pseudotyped GFP expressing HIV-1 resulted in increased numbers of GFP+ cells in the Leishmania-maturated MDMs as compared to control cells. Interestingly, a sub-population of Leishmania-maturated MDMs was found to have re-entered the cell cycle, as demonstrated by BrdU labeling. In conclusion, Leishmania infection of primary human monocytes promotes the induction of an S phase environment and elevated dNTP levels with notable elevation of HIV-1 expression in the setting of coinfection.

Leishmaniasis is a parasitic disease that infects several human host immune cells, including neutrophils, monocytes, and macrophages. Moreover, while HIV-1 infects monocytes and macrophages, only the infected macrophages productively release viral progenies. Importantly, patients coinfected with both pathogens progress more rapidly to AIDS. In this study, we examine how Leishmania major changes the cellular environment of monocytes in vitro. We found that Leishmania-infected monocytes actively mature into macrophages in the absence of GM-CSF, and that these cells up-regulate the expression of ribonucleotide reductase, an enzyme that catalyzes the formation of deoxynucleoside triphosphates (dNTPs). We confirmed the elevation of dNTP concentrations using a very sensitive dNTP assay for monocytes and monocyte-maturated macrophages. Collectively, these data support a model in which infection of monocytes with Leishmania elevates the intracellular dNTP pools, which is one of the natural anti-viral blocks to HIV-1 infection in monocytes and macrophages in patients.

The macrophage

Macrophages are a diverse phenotype of professional phagocytic cells derived from bone-marrow precursors and parent monocytes in the peripheral blood. They are essential for the maintenance and defence of host tissues, doing so by sensing and engulfing particulate matter and, when necessary, initiating a pro-inflammatory response. Playing such a vast number of roles in both health and disease, the activation phenotype of macrophages can vary greatly and is largely dependent on the surrounding microenvironment. These phenotypes can be mimicked in experimental macrophage models derived from monocytes and in conjunction with stimulatory factors, although given the complexity of in vivo tissue spaces these model cells are inherently imperfect. Furthermore, experimental observations generated in mice are not necessarily conserved in humans, which can hamper translational research. The following chapter aims to provide an overview of how macrophages and their parent cell-type, monocytes, are classified, their development through the myeloid lineage, and finally, the general function of macrophages.

HIV-1 infection of macrophages is dependent on evasion of innate immune cellular activation

OBJECTIVE

The cellular innate immune response to HIV-1 is poorly characterized. In view of HIV-1 tropism for macrophages, which can be activated via pattern recognition receptors to trigger antimicrobial defences, we investigated innate immune responses to HIV-1 by monocyte-derived macrophages.

DESIGN

In a model of productive HIV-1 infection, cellular innate immune responses to HIV-1 were investigated, at the level of transcription factor activation, specific gene expression and genome-wide transcriptional profiling. In addition, the viral determinants of macrophage responses and the physiological effect of innate immune cellular activation on HIV-1 replication were assessed.

RESULTS

Productive HIV-1 infection did not activate nuclear factor-kappaB and interferon regulatory factor 3 transcription factors or interferon gene expression (IFN) and caused remarkably small changes to the host-cell transcriptome, with no evidence of inflammatory or IFN signatures. Evasion of IFN induction was not dependent on HIV-1 envelope-mediated cellular entry, inhibition by accessory proteins or reverse transcription of ssRNA that may reduce innate immune cellular activation by viral RNA. Furthermore, IFNbeta priming did not sensitize responses to HIV-1. Importantly, exogenous IFNbeta or stimulation with the RNA analogue poly I:C to simulate innate immune activation invoked HIV-1 restriction.

CONCLUSION

We conclude that macrophages lack functional pattern recognition receptors for this virus and that HIV-1 tropism for macrophages helps to establish a foothold in the host without triggering innate immune cellular activation, which would otherwise block viral infection effectively.

Bacillus anthracis edema toxin suppresses human macrophage phagocytosis and cytoskeletal remodeling via the protein kinase A and exchange protein activated by cyclic AMP pathways

Bacillus anthracis, the etiological agent of anthrax, is a gram-positive spore-forming bacterium. It produces edema toxin (EdTx), a powerful adenylate cyclase that increases cyclic AMP (cAMP) levels in host cells. Because other cAMP-increasing agents inhibit key macrophage (MPhi) functions, such as phagocytosis, it was hypothesized that EdTx would exhibit similar suppressive activities. Our previous GeneChip data showed that EdTx downregulated MPhi genes involved in actin cytoskeleton remodeling, including protein kinase A (PKA). To further examine the role of EdTx during anthrax pathogenesis, we explored the hypothesis that EdTx treatment leads to deregulation of the cAMP-dependent PKA system, resulting in impaired cytoskeletal functions essential for MPhi activity. Our data revealed that EdTx significantly suppressed human MPhi phagocytosis of Ames spores. Cytoskeletal changes, such as decreased cell spreading and lowered F-actin content, were also observed for toxin-treated MPhis. Further, EdTx altered the protein levels and activity of PKA and exchange protein activated by cAMP (Epac), a recently identified cAMP-binding molecule. By using PKA- and Epac-selective cAMP analogs, we confirmed the involvement of both pathways in the inhibition of MPhi functions elicited by EdTx-generated cAMP. These results suggested that EdTx weakened the host immune response by increasing cAMP levels, which then signaled via PKA and Epac to cripple MPhi phagocytosis and interfered with cytoskeletal remodeling.

Genome-wide innate immune responses in HIV-1-infected macrophages are preserved despite attenuation of the NF-kappa B activation pathway

Macrophages contribute to HIV-1 infection at many levels. They provide permissive cells at the site of inoculation, augment virus transfer to T cells, generate long-lived viral reservoirs, and cause bystander cell apoptosis. A body of evidence suggests that the role of macrophages in cellular host defense is also compromised by HIV-1 infection. In this respect, macrophages are potent cells of the innate immune system that initiate and regulate wide-ranging immunological responses. This study focuses on the effect of HIV-1 infection on innate immune responses by macrophages at the level of signal transduction, whole genome transcriptional profiling, and cytokine secretion. We show that in an ex vivo model, M-CSF-differentiated monocyte-derived macrophages uniformly infected with replicating CCR5-tropic HIV-1, without cytopathic effect, exhibit selective attenuation of the NF-kappaB activation pathway in response to TLR4 and TLR2 stimulation. However, functional annotation clustering analysis of genome-wide transcriptional responses to LPS stimulation suggests substantial preservation of gene expression changes at the systems level, with modest attenuation of a subset of up-regulated LPS-responsive genes, and no effect on a selection of inflammatory cytokine responses at the protein level. These results extend existing reports of inhibitory interactions between HIV-1 accessory proteins and NF-kappaB signaling pathways, and whole genome expression profiling provides comprehensive assessment of the consequent effects on immune response gene expression. Unexpectedly, our data suggest innate immune responses are broadly preserved with limited exceptions, and pave the way for further study of the complex relationship between HIV-1 and immunological pathways within macrophages.

Transcriptional restriction of human immunodeficiency virus type 1 gene expression in undifferentiated primary monocytes

Monocytes are critical precursors of dendritic cells and macrophages, which play an important role in the pathogenesis of human immunodeficiency virus type 1 (HIV-1). HIV-1 postentry infection is blocked in undifferentiated monocytes in vitro, while the underlying mechanisms are not fully understood. HIV-1 Tat-mediated transactivation of the viral long terminal repeat (LTR) promoter is essential for HIV-1 transcription. Two critical cellular cofactors of HIV-1 Tat, cyclin T1 (CycT1) and cyclin-dependent kinase 9 (CDK9), are required for LTR-directed HIV-1 transcription. In addition to the previously identified restrictions in early viral life cycle, we find that HIV-1 gene expression is impaired in undifferentiated primary monocytes. Transfection of monocytes by nucleofection with HIV-1 proviral DNA could not produce infectious HIV-1. The lack of Tat transactivation of the LTR promoter correlated with the impaired HIV-1 gene expression in monocytes. Interestingly, heterokaryons between primary monocytes and a human embryonic kidney cell line restored Tat transactivation of LTR, suggesting that monocytes lack cellular factors required for Tat transactivation. CycT1 protein was undetectable in freshly isolated monocytes and induced in monocyte-differentiated macrophages, while the expression of CDK9 remained constant. Transient expression of CycT1 in undifferentiated monocytes could not rescue Tat transactivation, suggesting that CycT1 is not the only limiting factor of HIV-1 infection in monocytes. Furthermore, monocyte differentiation into macrophages appeared to enhance the phosphorylation of CDK9, which correlated with significantly increased HIV-1 infection in macrophages. Our results provide new insights into HIV-1 infection and regulation in primary monocytes and viral pathogenesis.

Erythromycin derivatives inhibit HIV-1 replication in macrophages through modulation of MAPK activity to induce small isoforms of C/EBPbeta

Macrophages (MPhis) are a major source of HIV-1 especially in patients with tuberculosis. There are MPhis that are permissive and those that restrict HIV-1. Regulation of hematopoietic cell kinase (Hck) activity and selective expression of CCAAT enhancer binding protein beta (C/EBPbeta) isoforms greatly contribute to determine distinct susceptibility of MPhis to HIV-1. Resistance is attributable to reduced expression of Hck and augmented expression of an inhibitory small isoform of C/EBPbeta. Derivatives of erythromycin A (EMA) EM201 and EM703 inhibit the replication of HIV-1 in tissue MPhis, at posttranscriptional and translational levels. We demonstrate that EM201 and EM703 convert tissue MPhis from HIV-1 susceptible to HIV-1 resistant through down-regulation of Hck and induction of small isoforms of C/EBPbeta. These drugs inhibit p38MAPK activation which is expressed only in susceptible tissue MPhis. Activated CD4(+)T cells stimulate the viral replication in HIV-1 resistant MPhis through down-regulation of small isoforms of C/EBPbeta via activation of ERK1/2. EM201 and EM703 can inhibit the MAPK activation and inhibit the burst of viral replication produced when CD4(+)T cells and MPhis interact. These EM derivatives may be highly beneficial for repression of residual HIV-1 in the lymphoreticular system of HIV-1-infected patients and offer great promise for the creation of new anti-HIV drugs for the future treatment of AIDS patients.

Granulocyte-monocyte colony-stimulating factor upregulates HIV-1 replication in monocyte-derived macrophages cultured at low density

The effects that granulocyte-monocyte colony-stimulating factor (GM-CSF) has on HIV-1 replication in monocyte-derived macrophage are controversial. We noted that groups reporting that GM-CSF inhibits HIV-1 replication performed their experiments at relatively high cell densities. To address this issue, we performed experiments at different macrophage densities. In cultures seeded at low cell densities, we find that adding GM-CSF during the first week of culture (ie, before infection, during maturation) increased viral replication compared with that in untreated controls in 10 of 11 donors with quantifiable HIV-1 replication. (No effects were observed if GM-CSF was added after the first week of culture.) In cultures seeded at the higher cell densities representative of those in some previous studies, adding GM-CSF during the first week reduced subsequent viral replication in 8 of 12 donors. In all cases in which GM-CSF reduced viral replication, however, the pH in the wells containing GM-CSF-treated cells dropped dramatically. Macrophages in these acidified cultures had numerous dark granules, suggesting that they were under stress. We conclude, contrary to previous reports, that GM-CSF usually enhances viral replication when cells are grown at low densities in which excessive medium acidification can be prevented. Our results illustrate the dramatic effects that in vitro tissue culture conditions can have when studying the effect of cytokines on HIV-1 replication.

Naturally occurring C-terminally truncated STAT5 is a negative regulator of HIV-1 expression

CD4(+) cells of most individuals infected with HIV-1 harbor a C-terminally truncated and constitutively activated form of signal transducer and activator of transcription-5 (STAT5 Delta). We report that the chronically HIV-infected U1 cell line expresses STAT5 Delta but not full-length STAT5. Granulocyte-macrophage colony-stimulating factor (GM-CSF) stimulation of U1 cells promoted early activation of STAT5 Delta and of extracellular signal regulated kinases (ERKs), followed by later activation of activator protein 1 (AP-1) and HIV expression. Inhibition of ERK/AP-1 by PD98,059 abolished, whereas either tyrphostin AG490 or a STAT5 small interfering RNA (siRNA) enhanced, virion production in GM-CSF-stimulated U1 cells. Chromatin immunoprecipitation demonstrated the induction of STAT5 Delta binding to STAT consensus sequences in the HIV-1 promoter together with a decreased recruitment of RNA polymerase II after 1 hour of GM-CSF stimulation of U1 cells. Down-regulation of STAT5 Delta by siRNA resulted in the up-regulation of both HIV-1 gag-pol RNA and p24 Gag antigen expression in CD8-depleted leukocytes of several HIV-positive individuals cultivated ex vivo in the presence of interleukin-2 but not of interleukin-7. Thus, the constitutively activated STAT5 Delta present in the leukocytes of most HIV-positive individuals acts as a negative regulator of HIV expression.

HIV and other lentiviral infections cause defects in neutrophil chemotaxis, recruitment, and cell structure: immunorestorative effects of granulocyte-macrophage colony-stimulating factor

Patients with HIV infection exhibit deficits in bacterial and fungal clearance, and possibly depressed innate immunity. In this study, we observed that neutrophils from HIV-infected patients have a profound defect in chemotaxis in response to endogenous (IL-8) and bacterial (fMLP) chemoattractants, which was directly correlated with peripheral CD4(+) lymphocyte levels but not plasma viral load. A similar chemotactic defect was observed in the feline immunodeficiency virus (FIV) model of HIV infection. Intravital microscopy of FIV-infected animals revealed marked impairment in the in vivo recruitment of leukocytes; specifically integrin-dependent neutrophil adhesion and emigration induced by bacterial products. Treatment of FIV-infected animals with GM-CSF re-established both neutrophil recruitment (rolling, adhesion, and emigration) and in vitro chemotaxis to the levels seen in uninfected animals. This restoration of neutrophil responses was not due to GM-CSF-mediated priming. Rather, HIV and FIV infections resulted in defective neutrophil development, with an ensuing reduction in neutrophil granularity and chemotactic receptor expression. GM-CSF therapy restored neutrophil granularity, implying restoration of normal neutrophil development. Together, our findings underscore the fundamental defects in innate immunity caused by lentivirus infections, while also indicating that GM-CSF may be a potential immunorestorative therapy for HIV-infected patients.

Functional heterogeneity of colony-stimulating factor-induced human monocyte-derived macrophages

OBJECTIVES

Macrophages (Mphis) have various functions and play a critical role in host defense and the maintenance of homeostasis. Mphis exist in every tissue in the body, but Mphis from different tissues exhibit a wide range of phenotypes with regard to their morphology, cell surface antigen expression and function, and are called by different names. However, the precise mechanism of the generation of macrophage heterogeneity is not known. In the present study, the authors examined the functional heterogeneity of Mphis generated from human monocytes under the influence of granulocyte-macrophage colony-stimulating factor (GM-CSF) and macrophage-CSF (M-CSF).

METHODOLOGY

CD14 positive human monocytes (Mos) were incubated with M-CSF and GM-CSF for 6-7 days to stimulate the generation of M-CSF-induced monocyte-derived Mphis (M-Mphis) and GM-CSF-induced monocyte-derived Mphis (GM-Mphis), respectively. The expression of cell surface antigens and several functions such as antigen presenting cell activity, susceptibility to oxidant stress, and the susceptibility to HIV-1 and mycobacterium tuberculosis infection were examined.

RESULTS

GM-Mphis and M-Mphis are distinct in their morphology, cell surface antigen expression, and functions examined. The phenotype of GM-Mphis closely resembles that of human Alveolar-Mphis (A-Mphis), indicating that CSF-induced human monocyte-derived Mphis are useful to clarify the molecular mechanism of heterogeneity of human Mphis, and GM-Mphis will become a model of human A-Mphis.

Inhibition of microglia multinucleated giant cell formation and induction of differentiation by GM-CSF using a porcine in vitro model

Multinucleated giant cell (MNGC) formation is an important histopathologic feature of AIDS dementia complex and tuberculous meningitis. We investigated the effect of several cytokines (GM-CSF, IFN-gamma, TNF-alpha, IL-3) and other stimuli (vaso-I, LPS, PMA) on MNGC formation in vitro by microglia from porcine neonatal brain. GM-CSF dose-dependently inhibited giant cell formation at physiological conditions (10 ng/ml) up till 4 days in culture. When confronted with a high concentration (1 microg/ml) they were 5.5 times less likely to form MNGC and 3.3 times more likely to develop a ramified morphology. In contrast, interferon-gamma (6 ng/ml) doubled the formation of MNGC. GM-CSF primed (4 days) microglia also produced significantly higher amounts of superoxide after PMA-stimulation. We conclude that GM-CSF leads microglia to a specific activation other than MNGC formation. Comparison of the present results with earlier reports on rodents reveals important inter-species differences.

Identification of granulocyte-macrophage colony-stimulating factor and lipopolysaccharide-induced signal transduction pathways that synergize to stimulate HIV type 1 production by monocytes from HIV type 1 transgenic mice

HIV-1-infected monocyte/macrophages located in lymph nodes and tissues are highly productive sources of HIV-1 and may function as a persistent reservoir contributing to the rebound viremia observed after highly active antiretroviral therapy is stopped. Mechanisms activating latently infected, primary monocyte/macrophages to produce HIV-1 were investigated using monocytes isolated from a transgenic mouse line carrying a full-length proviral clone of a monocyte-tropic HIV-1 isolate, HIV-1(JR-CSF), regulated by the endogenous long terminal repeat (LTR) (JR-CSF mice). Granulocyte-macrophage colony-stimulating factor (GM-CSF) combined with lipopolysaccharide (LPS) induced infectious HIV-1 production by JR-CSF mouse monocytes over 10-fold and 100-fold higher than that stimulated by GM-CSF or LPS alone, respectively. We examined mechanisms of GM-CSF synergy with LPS and demonstrated that GM-CSF up-regulated the LPS receptor, TLR-4, and also synergized with LPS to activate mitogen-activated protein (MAP) kinase/ERK kinase and the Sp1 transcription factor. Inhibitors of either MAP kinase/ERK kinase or p38 kinase but not PI 3-kinase potently suppressed GM-CSF and LPS-induced HIV-1 production by JR-CSF mouse monocytes. Because Sp1 is activated by both the MAP kinase/ERK kinase and p38 kinase pathways, we postulate that synergistic activation of these pathways by GM-CSF and LPS induced sufficient levels of Sp1 to activate the HIV-1 LTR in a Tat-independent manner and induced HIV-1 production by JR-CSF mouse monocytes. Thus, our study delineated the pathway of HIV-1 LTR activation by GM-CSF and LPS and indicated that JR-CSF transgenic mice may provide a new in vitro and in vivo system for investigating the mechanism by which inflammatory and infectious stimuli activate HIV-1 production from latently infected monocytes.

The use of growth factors and cytokines to treat opportunistic infections in HIV-1 disease

The success of highly active antiretroviral therapy (HAART) in reducing AIDS-related mortality means that in regions where HAART is available, HIV infection may now be regarded as a chronic disease. However the inability of HAART to eliminate HIV-1 from various anatomical and cellular reservoirs within the body means that HIV-infected individuals require life-long treatment with therapy that can have significant side effects. Management of HIV disease is therefore increasingly focused on drug-related toxicities and the improvement of current HAART regimens. Here we review the potential use of immunomodulatory cytokines to directly or indirectly stimulate the mononuclear phagocyte system as adjuncts to current HIV treatment as well as their use in the management of opportunistic infections in individuals who develop immunodeficiency. We argue that cytokines, which stimulate mononuclear phagocyte activity against opportunistic pathogens, may be useful for the treatment of individuals who develop recurrent opportunistic infections. Cytokines may act synergistically with antimicrobial agents to improve outcomes, which is of particular importance since recurrent infections frequently result in resistance to standard antimicrobial treatments. Before their use can be advocated however, given their toxicity and significant cost, the potential benefits of cytokines must be demonstrated in larger clinical trials.

CSF-induced and HIV-1-mediated distinct regulation of Hck and C/EBPbeta represent a heterogeneous susceptibility of monocyte-derived macrophages to M-tropic HIV-1 infection

Granulocyte/macrophage colony-stimulating factor (GM-CSF)-induced monocyte-derived macrophages (GM-MPhi) are permissive to M-tropic HIV-1 entry, but inhibit viral replication at posttranscriptional and translational levels, whereas M-CSF-induced macrophages (M-MPhi) produce a large amount of HIV-1. M-MPhi express a high level of Hck and a large isoform of C/EBPbeta, and HIV-1 infection increases the expression of Hck but not of C/EBPbeta. GM-MPhi express a high level of C/EBPbeta and a low level of Hck, and HIV-1 infection drastically increases the expression of a short isoform of C/EBPbeta but decreases that of Hck. Treatment of M-MPhi with antisense oligonucleotide for Hck (AS-Hck) not only suppresses the expression of Hck, but also stimulates the induction of the short isoform of C/EBPbeta and inhibits the viral replication. Treatment of GM-MPhi with a moderate amount of AS-C/EBPbeta not only inhibits the expression of the small isoform of C/EBPbeta preferentially, but also stimulates the induction of Hck and stimulates the virus production at a high rate. These results suggest that CSF-induced and HIV-1-mediated distinct regulation of Hck and small isoform of C/EBPbeta represent the heterogeneous susceptibility of tissue MPhi to HIV-1 infection, and the regulation of Hck and C/EBPbeta are closely related and these two molecules affect one another.

A controlled trial of granulocyte macrophage-colony stimulating factor during interruption of HAART

OBJECTIVES

To explore the effect of granulocyte macrophage colony stimulating factor (GM-CSF) on viral load and CD4 cell count during interruption of highly active antiretroviral therapy (HAART).

METHODS

Patients on effective HAART (CD4 cell count > 400 x 10(6)/l; viral load < 50 HIV RNA copies/ml) were randomized to one of two groups: 12 weeks' treatment interruption plus, during the first 4 weeks, 300 microg GM-CSF (Leucomax-Novartis) by subcutaneous injection three times weekly (GM-CSF group); 12 weeks' scheduled treatment interruption (STI-only group). Viral load, CD4 cell count, clinical events and side effects of treatment were monitored.

RESULTS

Thirty-three patients, 15 in the GM-CSF group and 18 in the STI-only group, were evaluated according to the intention-to-treat principle. The two groups were well matched with regard to pre-HAART viral loads and CD4 cell counts. During STI, viraemia was approximately two to three times lower in the group receiving GM-CSF (max 4.97 versus 5.45 in STI-only group; P = 0.03). Fifteen out of 17 patients in the STI-only group showed a decrease in their CD4 cell count between weeks 0 and 4 (median decrease 231 x 10(6) cells/l; P < 0.001); there was no such tendency in the GM-CSF group (P = non-significant when comparing CD4 cell counts at weeks 0 and 4). The median CD4 cell AUC (area under the curve) from week 0 to week 12 was higher in the GM-CSF group (9166 cells.week) than in patients without GM-CSF (7257), P = 0.02. GM-CSF produced local reactions in 88% of patients, and generalized symptoms such as fever, back pain or headache in 82% of patients. Seventy-six percent of patients completed the planned course of 12 injections.

CONCLUSIONS

The administration of GM-CSF blunted the viral rebound following interruption of HAART, and largely prevented a decrease of CD4 cell counts during a 12-weeks-treatment interruption. A better understanding of the underlying mechanism(s) may help to identify synergistic treatment targets and improved administration protocols to enhance control of chronic HIV infection.

The influence of cytokines, chemokines and their receptors on HIV-1 replication in monocytes and macrophages

Monocytes, macrophages and dendritic cells play an important role in the initial infection and contribute to its pathogenesis throughout the course of infection. Myeloid cells express CD4 and chemokine receptors known for HIV-1 fusion and entry. The beta-chemokine receptor, CCR5, is the major co-receptor in conjunction with CD4 for macrophage (M)-tropic or (R5) isolates of HIV-1, whereas the alpha-chemokine receptor, CXCR4, facilitates entry of T-tropic or (X4) HIV-1 strains. Cells of myeloid lineage may be infected predominantly with R5- strains, although infection with dual-tropic isolates of HIV-1 (exhibiting the capacity to use CCR-5 and/or CXCR-4 for entry) or some strains of X4- isolates has also been reported. The expression of chemokine receptors, HIV-1 infection and replication is under continuous regulation by a complex cytokine network produced by a variety of cells. The effects of cytokines/chemokines on HIV-1 replication in cells of myeloid lineage can be inhibitory (IFN-alpha, IFN-beta, IFN-gamma, GM-CSF, IL-10, IL-13 and IL-16 and beta-chemokines), stimulatory (M-CSF, TNF-alpha, TNF-beta, IL-1, IL-6) or bifunction al, that is both inhibitory and stimulatory (IL-4). This review focuses on the overall expression of chemokine receptors on cells of myeloid lineage and considers the mechanisms of entry of R5-, X4- and dual-tropic strains of HIV-1 into these cells. The effects of cytokines/chemokines on viral entry and productive HIV-1 infection are also reviewed.

Granulocyte macrophage colony stimulating factor is elevated in alveolar macrophages from sheep naturally infected with maedi-visna virus and stimulates maedi-visna virus replication in macrophages in vitro

Infection by maedi-visna virus, a lentivirus of sheep, leads to chronic inflammatory reactions of various tissues. In this report we have analysed the role of specific cytokines in the disease process. A significant increase in expression of interleukin-6, interleukin-10, granulocyte macrophage-colony stimulating factor (GM-CSF) and transforming growth factor-beta1 mRNA was observed in alveolar macrophages isolated from the lungs of naturally infected animals when compared with lungs of seronegative controls. Levels of GM-CSF mRNA expression in alveolar macrophages correlated with the presence of lung lesions, but there was no correlation of interleukin-10, interleukin-6, tumour necrosis factor-alpha and transforming growth factor-beta1 mRNA levels in alveolar macrophages from animals with pulmonary lesions. In vitro investigation showed that GM-CSF in the range 0.1-10 ng/ml induced a significant increase in viral p25 production after 7 days in acutely infected blood monocyte-derived macrophages. The production of p25 peaked between 7 and 14 days exposure to 10 ng/ml of GM-CSF. Quantitative polymerase chain reaction showed that the level of viral DNA in monocyte-derived macrophages was dose-dependent following GM-CSF treatment in the range 0.1-100 ng/ml after 7 days. Viral mRNA expression was also enhanced. These findings indicate a role for GM-CSF in the pathogenesis of lymphoid interstitial pneumonia in infected animals.

Human GM-CSF induces HIV-1 LTR by multiple signalling pathways

Human immunodeficiency virus type-1 (HIV-1) gene expression is known to be affected by numerous cytokines or growth factors. However, the effect of granulocyte-macrophage colony-stimulating factor (GM-CSF) on long terminal repeat (LTR)-mediated transcription of HIV-1 still remains unknown. By transient transfection experiments with HIV-1 LTR reporter constructs, we showed that strong LTR-mediated activation was induced by GM-CSF in mouse Ba/F3 cells expressing human GM-CSF receptors (GM-CSFR). Mutational analysis of the HIV-1 LTR reporters revealed that both NF-kappaB and Sp1 binding sites play important roles as positive regulatory elements. Analysis of various mutants of the cytoplasmic region of GM-CSFR indicated that both the conserved membrane proximal region and tyrosine residues located in the distal part of the beta subunit were required for HIV-1 LTR activation. Possible involvement of MAPK and PI3-K signalling pathways was suggested by the partial inhibition by wortmannin, a specific inhibitor of the PI3-K pathway, and enhancement by constitutively active MEK1, of HIV-1 LTR activation. However, the MEK1 pathway is not essential since MEK1 inhibitor PD98059 did not suppress GM-CSF-induced HIV-1-LTR activation. Further analyses of GM-CSFR mutants suggested that some other unknown signalling pathway also participates in GM-CSF-induced HIV-1 LTR activation. Taken together, the data suggest that GM-CSF could upregulate the LTR-driven transcription of HIV-1 through modulation of NF-kappaB and SP1 by multiple signalling pathways.

Functional heterogeneity of colony-stimulating factor-induced human monocyte-derived macrophages

Macrophages have various functions and play a critical role in host defense and the maintenance of homeostasis. However, macrophages are heterogeneous and exhibit a wide range of phenotypes with regard to their morphology, cell surface antigen expression, and function. When blood monocytes are cultured in medium alone in vitro, monocytes die, and colony-stimulating factors (CSFs) such as macrophage (M)-CSF or granulocyte-macrophage (GM)-CSF are necessary for their survival and differentiation into macrophages. However, M-CSF-induced monocyte-derived macrophages (M-Mphi) and GM-CSF-induced monocyte-derived macrophages (GM-Mphi) are distinct in their morphology, cell surface antigen expression, and functions, including Fcgamma receptor mediated-phagocytosis, H2O2 production, H2O2 sensitivity, catalase activity, susceptibility to human immunodeficiency virus type 1 and Mycobacterium tuberculosis, and suppressor activity. The characteristics of GM-Mphi resemble those of human alveolar macrophages.

Active cellular infection of myeloid cells is required for HIV-1-mediated suppression of interleukin-12 p40 expression

Immunodeficiency during HIV infection is associated with impaired production of interleukin-12 (IL-12). Here we examine the requirement for active cellular infection, the role of other cytokines, and the molecular target of HIV-mediated suppression of IL-12. The reduction in LPS-induced IL-12 p40 protein and mRNA following acute in vitro HIV infection of THP-1 cells and monocytes was not attributed to IL-10 or TGF-beta activity and was not restored by priming with IL-4, IL-13, or IFN-gamma. Suppression of IL-12 was dependent upon active cellular infection and replication and not due to any soluble host or viral factors in HIV-infected cultures. Significant reduction in transcription of IL-12 p40 was observed following acute HIV infection. These results suggest that impaired IL-12 production in HIV-infected myeloid cells occurs, in part, via disruption of IL-12 p40 gene expression in a manner that requires cellular infection, highlighting the need to study myeloid cells in isolation during acute HIV-1 infection.

Interleukin-10 contributes development of macrophage suppressor activities by macrophage colony-stimulating factor, but not by granulocyte-macrophage colony-stimulating factor

Macrophages are known to possess suppressor activities in immune responses. To determine the effects of GM-CSF and M-CSF on the expression of macrophage suppressor activities, monocyte-derived macrophages cultured with GM-CSF (GM-Mphis) were compared with those cultured with M-CSF (M-Mphis) for antigen-specific proliferation and interferon-gamma (IFN-gamma) production by lymphocytes. Both GM-Mphis and M-Mphis equally suppressed lymphocyte proliferation, but only M-Mphis suppressed IFN-gamma production in response to purified protein derivative (PPD). M-Mphis, but not GM-Mphis, released IL-10 not only in the course of macrophage differentiation but also in response to PPD after maturation to macrophages. From the results that (i) exogenous IL-10 suppressed IFN-gamma production, but not proliferation of lymphocytes, and that (ii) neutralizing antibody to IL-10 reversed suppressor activities of M-Mphis on IFN-gamma production, but not lymphocyte proliferation, it appeared that IL-10 was the major factor responsible for suppression of IFN-gamma production. Thus, these results suggest that only M-CSF augments IL-10-dependent suppressor activity of macrophages on IFN-gamma production and that both GM-CSF and M-CSF induce IL-10-independent macrophage suppressor activity on lymphocyte proliferation.

Human alveolar macrophages and granulocyte-macrophage colony-stimulating factor-induced monocyte-derived macrophages are resistant to H2O2 via their high basal and inducible levels of catalase activity

Human alveolar macrophages (A-MPhi) and macrophages (MPhi) generated from human monocytes under the influence of granulocyte-macrophage colony-stimulating factors (GM-MPhi) express high levels of catalase activity and are highly resistant to H(2)O(2). In contrast, MPhi generated from monocytes by macrophage colony-stimulating factors (M-MPhi) express low catalase activity and are about 50-fold more sensitive to H(2)O(2) than GM-MPhi or A-MPhi. Both A-MPhi and GM-MPhi but not M-MPhi can induce catalase expression in both protein and mRNA levels when stimulated with H(2)O(2) or zymosan. M-MPhi but not GM-MPhi produce a large amount of H(2)O(2) in response to zymosan or heat-killed Staphylococcus aureus. These findings indicate that GM-MPhi and A-MPhi but not M-MPhi are strong scavengers of H(2)O(2) via the high basal level of catalase activity and a marked ability of catalase induction and that catalase activity of MPhi is regulated by colony-stimulating factors during differentiation.

Cytokines and HIV-1: interactions and clinical implications

Cytokines play an important role in controlling the homoeostasis of the immune system. Infection with HIV results in dysregulation of the cytokine profile in vivo and in vitro. During the course of HIV-1 infection secretion of T-helper type 1 (Th1) cytokines, such as interleukin (IL)-2, and antiviral interferon (IFN)-gamma, is generally decreased, whereas production of T helper type 2 (Th2) cytokines, IL-4, IL-10, proinflammatory cytokines (IL-1, IL-6, IL-8) and tumour necrosis factor (TNF)-alpha, is increased. Such abnormal cytokine production contributes to the pathogenesis of the disease by impairing cell-mediated immunity. A number of cytokines have been shown to modulate in vitro HIV-1 infection and replication in both CD4 T lymphocytes and cells of macrophage lineage. HIV-inductive cytokines include: TNF-alpha, TNF-beta, IL-1 and IL-6, which stimulate HIV-1 replication in T cells and monocyte-derived macrophages (MDM), IL-2, IL-7 and IL-15, which upregulate HIV-1 in T cells, and macrophage-colony stimulating factor, which stimulates HIV-1 in MDM. HIV-suppressive cytokines include: IFN-alpha, IFN-beta and IL-16, which inhibit HIV-1 replication in T cells and MDM, and IL-10 and IL-13, which inhibit HIV-1 in MDM. Bifunctional cytokines such as IFN-gamma, IL-4 and granulocyte-macrophage colony-stimulating factor have been shown to have both inhibitory and stimulatory effects on HIV-1. The beta-chemokines, macrophage-inflammatory protein (MIP)-1alpha, MIP-1beta and RANTES are important inhibitors of macrophage-tropic strains of HIV-1, whereas the alpha-chemokine stromal-derived factor-1 suppresses infection of T-tropic strains of HIV-1. This review outlines the interactions between cytokines and HIV-1, and presents clinical applications of cytokine therapy combined with highly active antiretroviral therapy or vaccines.

Use of serial analysis of gene expression (SAGE) technology

Serial analysis of gene expression, or SAGE, is an experimental technique designed to gain a direct and quantitative measure of gene expression. The SAGE method is based on the isolation of unique sequence tags (9-10 bp in length) from individual mRNAs and concatenation of tags serially into long DNA molecules for a lump-sum sequencing. The SAGE method can be applied to the studies exploring virtually any kinds of biological phenomena in which the changes in cellular transcription are responsible. SAGE is a highly competent technology that can not only give a global gene expression profile of a particular type of cell or tissue, but also help us identify a set of specific genes to the cellular conditions by comparing the profiles constructed for a pair of cells that are kept at different conditions. In this review, we present an outline of the original method, several studies achieved by using the method as a major strategic tool, technological difficulties and intrinsic problems that emerged, and improvements and modifications of the method to cope with these drawbacks. We then present our modified SAGE procedure that generates longer sequence tags (14 bp) rather in detail, and the profile (80K profile) derived from HeLa cells that is composed of 80000 tags obtained from a single library. In addition, a series of smaller profiles (2, 4, 10, 20 and 40K) was made by dividing the 80K profile. When we compared these smaller profiles with respect to tag counts for a number of genes, it became apparent that counts of most gene tags increase stably and constantly as the size of profiles increase, while several genes do not. This may be another problem we have to keep in mind, when the profiles are compared for the identification of 'specific genes'.

Use of cytokines in human immunodeficiency virus-infected patients: colony-stimulating factors, erythropoietin, and interleukin-2

The recombinant human cytokines granulocyte colony-stimulating factor (G-CSF), granulocyte-macrophage colony-stimulating factor (GM-CSF), erythropoietin, and interleukin-2 (IL-2) have been manufactured and licensed. Studies have been carried out that investigate the use of G-CSF and GM-CSF to reverse leukopenia, as adjunctive therapy for HIV-associated infections and for novel approaches to treat HIV infection, including stem cell mobilization. In addition, studies that identified the role of erythropoietin in the management of anemia have been performed. Furthermore, the abilities of G-CSF and erythropoietin to permit the continued use of marrow suppressive agents that are key in managing HIV infection have been assessed. The aim of this review is to summarize these studies and to describe the reports that evaluate the use of IL-2 to enhance elevation of CD4 cell counts mediated by highly active antiretroviral therapy. This summary is important to the treating clinician in that it identifies the optimal use of these cytokines in current clinical practice as well as their potential future roles.

Granulocyte-macrophage colony-stimulating factor inhibits HIV-1 replication in monocyte-derived macrophages

BACKGROUND

Previous studies of the effect of granulocyte-macrophage colony-stimulating factor (GM-CSF) on HIV-1 replication in macrophages have had inconsistent results, variously reporting no effect, augmentation or inhibition of viral replication.

OBJECTIVE

To investigate the regulation of HIV-1 in monocyte-derived macrophages (MDM) by GM-CSF in vitro.

METHODS

The role of GM-CSF on HIV-1 replication was assessed as supernatant and intracellular p24 antigen concentrations and by HIV-1 DNA and mRNA production under different culture conditions. Expression of CD4 and CCR5 receptors was examined. The effect of GM-CSF with an E21R mutation, which binds only to the alpha-chain of GM-CSF receptor, was used as an additional control.

RESULTS

GM-CSF consistently suppressed HIV-1 replication in human MDM in vitro, as assessed by supernatant and intracellular p24 antigen concentrations and HIV-1 gag mRNA expression. The inhibitory effect of GM-CSF on HIV-1 replication was observed regardless of HIV-1 strain, source of GM-CSF, stage of MDM maturation or timing of GM-CSF exposure in relation to HIV-1 infection. The effect was dose dependent and reversed by addition of a neutralizing monoclonal antibody (4D4). Flow cytometric analysis of surface expression of CD4 and CCR5 indicates that GM-CSF does not affect HIV-1 entry into MDM. Analysis of intracellular HIV-1 DNA and mRNA suggests that HIV-1 replication is inhibited at or before transcription. E21R GM-CSF had no effect on HIV-1 replication in MDM.

CONCLUSIONS

GM-CSF regulates HIV-1 replication in MDM, inhibiting HIV-1 replication through binding to the beta-chain of the GM-CSF receptor.

Chemokine receptor-usage of clinical HIV-1 isolates obtained from patients with HIV-1 infection in late clinical stages using PHA-blast

In the present sudy, chemokine receptor-usage of primary HIV-1 isolates was examined using U87-CD4 cells expressing chemokine receptors CCR3, CCR5 and CXCR4. HIV-1 was isolated from the peripheral blood mononuclear cells (PBMC) and/or plasma of eight HIV-1-infected individuals in late CDC-II and CDC-IV clinical stages using PHA-blast prepared from the PBMC of healthy blood donors. The primary HIV-1 isolates from patients in late CDC-II stage rarely infected monocyte-derived macrophages in the present study, whereas most isolates from patients in the CDC-IV stage infected the macrophages. In the experiments using U87-CD4 cells expressing chemokine receptors, the isolates from patients in the late CDC-II stage infected U87-CD4 cells expressing CXCR4, but not U87-CD4 cells expressing CCR5. In contrast, most isolates from patients in the CDC-IV stage infected both U87-CD4 cells expressing CXCR4 or CCR5. The isolates which infected both U87-CD4 cells were supposed to contain dual tropic HIV-1 or a mixture of CXCR4-tropic and CCR5-tropic HIV-1s. Analysis of the deduced amino acid sequence of the V3 region in proviral env gene showed that the V3 region in U87-CD4 cells infected with CXCR4-tropic HIV-1 isolates was largely different from that in the cells infected with CCR5-tropic isolates, but were highly similar to that in cells infected with dual tropic isolates. These results suggest that PHA-blasts may preferentially support the replication of the CXCR4-tropic and dual tropic HIV-1s, and that CXCR4-tropic and dual tropic HIV-1s are also present in peripheral blood from patients in the late stage of the asymptomatic phase.

Simple chemicals can induce maturation and apoptosis of dendritic cells

As is well known in the case of Langerhans cells, dendritic cells (DCs) play a crucial role in the initiation of immunity to simple chemicals such as noted in the contact hypersensitivity. Because DCs are scattered in non-lymphoid organs as immature cells, they must be activated to initiate primary antigen-specific immune reactions. Therefore, we hypothesized that some simple chemicals must affect the function of DCs. In this paper, we first demonstrated that human monocyte-derived DCs responded to such simple chemicals as 2, 4-dinitrochlorobenzene (DNCB), 2,4,6-trinitrochlorobenzene (TNCB), 2, 4-dinitrofluorobenzene (DNFB), NiCl2, MnCl2, CoCl2, SnCl2, and CdSO4 by augmenting their expression of CD86 or human leucocyte antigen-DR (HLA-DR), down-regulating c-Fms expression or increasing their production of tumour necrosis factor-alpha (TNF-alpha). In addition, the DCs stimulated with the chemicals demonstrated increased allogeneic T-cell stimulatory function. Next, we found that, among these chemicals, only NiCl2 and CoCl2 induced apoptosis in them. Finally, we examined the effects of these chemicals on CD86 expression by three different macrophage subsets and DCs induced from the cultures of human peripheral blood monocytes in the presence of macrophage colony-stimulating factor (M-CSF), M-CSF + interleukin-4 (IL-4), granulocyte-macrophage colony-stimulating factor (GM-CSF), and GM-CSF + IL-4, respectively. Among them, only DCs dramatically augmented their expression of CD86. These observations have revealed unique characteristics of DCs, which convert chemical stimuli to augmentation of their antigen presenting function, although their responses to different chemicals were not necessarily uniform in the phenotypic changes, cytokine production or in the induction of apoptosis.

Role of naturally occurring basic amino acid substitutions in the human immunodeficiency virus type 1 subtype E envelope V3 loop on viral coreceptor usage and cell tropism

To assess the role of naturally occurring basic amino acid substitutions in the V3 loop of human immunodeficiency virus type 1 (HIV-1) subtype E on viral coreceptor usage and cell tropism, we have constructed a panel of chimeric viruses with mutant V3 loops of HIV-1 subtype E in the genetic background of HIV-1LAI. The arginine substitutions naturally occurring at positions 8, 11, and 18 of the V3 loop in an HIV-1 subtype E X4 strain were systematically introduced into that of an R5 strain to generate a series of V3 loop mutant chimera. These chimeric viruses were employed in virus infectivity assays using HOS-CD4 cells expressing either CCR5 or CXCR4, peripheral blood mononuclear cells, T-cell lines, or macrophages. The arginine substitution at position 11 of the V3 loop uniformly caused the loss of infectivity in HOS-CD4-CCR5 cells, indicating that position 11 is critical for utilization of CCR5. CXCR4 usage was conferred by a minimum of two arginine substitutions, regardless of combination, whereas arginine substitutions at position 8 and 11 were required for T-cell line tropism. Nonetheless, macrophage tropism was not conferred by the V3 loop of subtype E R5 strain per se. We found that the specific combinations of amino acid changes in HIV-1 subtype E env V3 loop are critical for determining viral coreceptor usage and cell tropism. However, the ability to infect HOS-CD4 cells through either CXCR4 or CCR5 is not necessarily correlated with T-cell or macrophage tropism, suggesting that cellular tropism is not dictated solely by viral coreceptor utilization.

CD8+ T cell-mediated enhancement of tumour necrosis factor-alpha (TNF-alpha) production and HIV-1 LTR-driven gene expression in human monocytic cells is pertussis toxin-sensitive

HIV replication and LTR-mediated gene expression can be modulated by CD8+ T cells in a cell type-dependent manner. We have previously shown that supernatants of activated CD8+ T cells of HIV-infected individuals greatly enhanced p24 levels in human macrophages infected with NSI or SI primary isolates of HIV-1. Here we have examined the effect of culture with CD8+ T cell supernatants on HIV-1 LTR-mediated gene expression in monocytic cells. CD8+ T cell supernatants enhanced LTR-mediated gene expression in U38 cells activated with Tat in the absence or presence of phorbol myristate acetate (PMA) and ionomycin or TNF-alpha. Further, enhancement of LTR-mediated gene expression and virus replication in U38 cells and U1 cells, respectively, was pertussis toxin-sensitive. The enhancement of gene expression and virus replication was associated with increased levels of TNF-alpha and was significantly abrogated by antibody to TNF-alpha. In contrast, the suppression of LTR-mediated gene expression by CD8+ T cell supernatants in Jurkat T cells was not pertussis toxin-sensitive and TNF-alpha levels were not affected. These results demonstrate that factors produced by CD8+ T cells utilize different cellular pathways to mediate their effects on HIV transcription and replication in different cell types.

The inhibitory effect of RANTES on the infection of primary macrophages by R5 human immunodeficiency virus type-1 depends on the macrophage activation state

We investigated whether culture conditions could affect the RANTES antiviral effect on human immunodeficiency virus type 1 (HIV-1) infection of primary macrophages. Monocyte-derived macrophages (MDM) were obtained either as (1) the adherent cells of 5-day cultures of blood mononuclear cells (PBMC), followed by 2 days without nonadherent PBMC or added cytokines (MDM-5d), or (2) as the adherent cells recovered from 1-h incubation of PBMC, which were cultured for 7 days with macrophage colony-stimulating factor (M-CSF; MDM-MCSF). Infection of MDM-5d from different donors with HIV-1 R5 strains was reproducibly inhibited by RANTES (IC50 < or = 10 nM), but infection of MDM-MCSF was not inhibited by > or = 100 nM RANTES, even when added at initiation of cultures, although it was still inhibited by a CD4 antibody. RANTES had no antiviral effect when MDM-5d were treated with physiological concentrations of M-CSF or GM-CSF before infection. CCR5 and CXCR4 expression as well as that of other cell surface molecules, including adhesion molecules, was not affected by the cytokines. MDM-MCSF from delta 32CCR5 homozygous individuals did not render them permissive to HIV-1, suggesting that it is unlikely that the virus uses another coreceptor. RANTES binding to MDM was chondroitin sulfate, but not heparan sulfate, dependent, and RANTES bound more efficiently to MDM-5d than to MDM-MCSF. Chondroitin sulfate removal partially offset the RANTES antiviral effect for MDM-5d. Thus RANTES anti-HIV-1 activity for primary macrophages depends on culture conditions and their consequent activation status, which may lead to differences in proteoglycan surface expression. These data may be relevant for the development of chemokine-based therapy for HIV-1 infection.

Restricted HIV type 1 replication under serum-free culture conditions in human monocyte-derived macrophages

Monocytes (MOs) and macrophages (MACs) are well-known targets for HIV-1 infection. Even though the virus load is contributed mainly to lymphocytes during the asymptomatic phase of infection, the expression of HIV-1 in MO/MACs seems to be important for the course of the disease. To establish a model for restricted HIV-1 expression in MACs in vitro, we cultured MO-derived MACs under different culture conditions and analyzed their susceptibility to HIV-1 infection as well as their capacity for virus replication in vitro. MACs cultured under serum-free conditions with M-CSF (M-MACs) remain viable and functionally active as assessed by the analysis of cytokine production. In addition, the levels of CD4, CD14, CCR5, and HLA-DR expression are comparable to those of serum-derived MACs (SER-MACs). However, serum-free MACs were less susceptible to HIV-1 infection, with only 9.5+/-4.5% (mean+/-SEM) of all cells being p24 antigen positive on day 22 as compared with 51+/-9% under serum conditions (p < 0.005). Reverse transcriptase (RT) activity in the culture supernatant of M-MACs was always about 100-fold lower than that of SER-MACs even when comparable amounts of cells were infected. The addition of serum to serum-free cultures increased the percentage of HIV-1 p24 antigen-positive cells (21+/-8% positive cells on day 22) and increased the RT activity, indicating that serum factors could be important for HIV-1 replication in MACs. Therefore we also switched SER-MACs to serum-free culture conditions and found a sharp decrease in RT activity. However, the RT level could always be rescued by the addition of serum, even after a long serum-free culture period. This effect was dependent on the serum concentration added, with as little as 0.1% serum being effective in reestablishing viral production as measured by RT activity. In conclusion, we show that serum has an important role in the replication of HIV-1 in MACs. Our results suggest that besides the role of CD4 and CCR5 other microenvironmental factors, e.g., growth factors, cytokines, or hormones, which are not provided by the target cell itself, are involved in the regulation of MAC infection and of replication by HIV-1.

Cytokine regulation of human immunodeficiency virus type 1 entry and replication in human monocytes/macrophages through modulation of CCR5 expression

Human macrophages express chemokine receptors that act as coreceptors for human immunodeficiency virus type 1 (HIV-1) and are major targets for HIV-1 infection in vivo. The effects of cytokines on HIV-1 infection of macrophages and on the expression of CCR5, the principal coreceptor for macrophage-tropic viruses, have now been investigated. Expression of CCR5 on the surface of freshly isolated human monocytes was virtually undetectable by flow cytometry with the monoclonal antibody 5C7. However, after culture of monocytes for 48 h in serum-free medium, approximately 30% of the resulting macrophages expressed CCR5 and the cells were susceptible to infection by macrophage-tropic HIV-1. Addition of either macrophage colony-stimulating factor (M-CSF) or granulocyte-macrophage colony-stimulating factor (GM-CSF) to the cultures markedly increased both the extent of HIV-1 entry and replication as well as surface expression of CCR5. In contrast, addition of the T-helper 2 (Th2) cell-derived cytokine interleukin-4 (IL-4) or IL-13 prevented the expression of CCR5 induced by culture in medium alone, and IL-4 inhibited virus entry, replication, and cytopathicity under these conditions. IL-4 or IL-13 also prevented the stimulatory effects of M-CSF or GM-CSF on CCR5 expression as well as HIV-1 entry and replication. In addition, IL-4 reversed the increase in CCR5 expression induced by pretreatment of cells with M-CSF. Although IL-10 also inhibits HIV-1 replication in macrophages, it did not suppress surface CCR5 expression induced by colony-stimulating factors. These results indicate that the cytokine environment determines the susceptibility of macrophages to HIV-1 infection by various mechanisms, one of which is the regulation of HIV-1 coreceptor expression.

A New Cytokine-Dependent Monoblastic Cell Line With t(9;11)(p22;q23) Differentiates to Macrophages With Macrophage Colony-Stimulating Factor (M-CSF) and to Osteoclast-Like Cells With M-CSF and Interleukin-4

Monocytes/macrophages exert a series of important functions in vivo. To facilitate detailed investigation of their functional capacity and the mechanism leading to their differentiation, several cell lines have been established from primary material. We present here a new human monoblastic cell line, designated UG3. UG3 cells are characterized by the following features. (1) UG3 cells harbor the t(9;11)(p22;q23) translocation that results in fusion of the MLL and the AF9 genes and produce the corresponding AF9-MLL and MLL-AF9 fusion transcripts. (2) UG3 cells rely on the presence of exogenous growth factors for viability and proliferation, such as interleukin-3 (IL-3), granulocyte-macrophage colony-stimulating factor (GM-CSF), granulocyte colony-stimulating factor (G-CSF), or macrophage colony-stimulating factor (M-CSF). (3) When cultured in the presence of G-CSF, UG3 cells differentiate along the granulocytic lineage, as evidenced by segmentation of nuclei and positive staining for neutrophilic alkaline phosphatase and peroxidase. (4) When cultured in the presence of GM-CSF or M-CSF, UG3 cells differentiate into mature macrophages while preserving surface expression of CD14 and CD68 and also start to release cytokines into cell-culture supernatants. Under these culture conditions, UG3 cells also take up acetylated LDL. (5) When cultured in the presence of M-CSF and IL-4, UG3 cells differentiate into osteoclast-like multinucleated giant cells capable of bone resorption and display tartrate-resistant acid phosphatase (TRAP) activity. UG3 cells thus provide features to qualify them as a useful model to further investigate the mechanism underlying these processes and also to further elucidate the functional role of mature monocytes/macrophages or osteoclasts.

A New Cytokine-Dependent Monoblastic Cell Line With t(9;11)(p22;q23) Differentiates to Macrophages With Macrophage Colony-Stimulating Factor (M-CSF) and to Osteoclast-Like Cells With M-CSF and Interleukin-4

Monocytes/macrophages exert a series of important functions in vivo. To facilitate detailed investigation of their functional capacity and the mechanism leading to their differentiation, several cell lines have been established from primary material. We present here a new human monoblastic cell line, designated UG3. UG3 cells are characterized by the following features. (1) UG3 cells harbor the t(9;11)(p22;q23) translocation that results in fusion of the MLL and the AF9 genes and produce the corresponding AF9-MLL and MLL-AF9 fusion transcripts. (2) UG3 cells rely on the presence of exogenous growth factors for viability and proliferation, such as interleukin-3 (IL-3), granulocyte-macrophage colony-stimulating factor (GM-CSF), granulocyte colony-stimulating factor (G-CSF), or macrophage colony-stimulating factor (M-CSF). (3) When cultured in the presence of G-CSF, UG3 cells differentiate along the granulocytic lineage, as evidenced by segmentation of nuclei and positive staining for neutrophilic alkaline phosphatase and peroxidase. (4) When cultured in the presence of GM-CSF or M-CSF, UG3 cells differentiate into mature macrophages while preserving surface expression of CD14 and CD68 and also start to release cytokines into cell-culture supernatants. Under these culture conditions, UG3 cells also take up acetylated LDL. (5) When cultured in the presence of M-CSF and IL-4, UG3 cells differentiate into osteoclast-like multinucleated giant cells capable of bone resorption and display tartrate-resistant acid phosphatase (TRAP) activity. UG3 cells thus provide features to qualify them as a useful model to further investigate the mechanism underlying these processes and also to further elucidate the functional role of mature monocytes/macrophages or osteoclasts.

Effect of GM-CSF on HIV-1 replication in monocytes/macrophages in vivo and in vitro: a review

Cells of macrophage lineage constitute the main cellular target of Human Immunodeficiency Virus type 1 (HIV-1). Replication of HIV-1 in monocyte/macrophages is generally augmented by factors promoting their differentiation. Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a key regular of the differentiation of cells of macrophage lineage. The effects of GM-CSF on HIV-1 replication in vitro are still controversial. Most of the published studies suggest that GM-CSF upregulates HIV-1 expression in both primary cultured macrophages and promonocytic cell lines. There have also been reports demonstrating that GM-CSF does not affect HIV-1 replication in cells of macrophage lineage or that GM-CSF can actually suppress HIV-1 expression. In vivo, GM-CSF administrated to HIV-positive patients at any stage of disease, without any antiretroviral therapy, appears to increase HIV-1 activity. The possible mechanism by which GM-CSF might affect HIV-1 replication in macrophages remains unclear.

Chemokine receptor regulation and HIV type 1 tropism in monocyte-macrophages

Monocyte-macrophages can be productively infected by CCR5-specific, but not CXCR4-specific, HIV-1. This could be due either to the absence of this chemokine receptor in this cell lineage or to other, yet undefined cellular cofactors that modulate the coreceptor activity of the CXCR4 in these cells. To investigate the basis of macrophage tropism, we studied the expression of CCR5 and CXCR4, as well as several of the other CC chemokine receptors, on monocyte-macrophages at different stages of differentiation. We found that on fresh monocytes, CXCR4 was relatively abundant, but it fell to barely detectable levels in culture over 24 hr and maintained this low level of expression during differentiation in vitro. Some donor macrophages appeared to express CXCR4 at levels comparable to CCR5. In contrast, CCR5 expression was low on fresh monocytes but increased on in vitro differentiation. Taken together, the results show that monocyte-macrophage differentiation is associated with a differential expression of chemokine receptors that may contribute to, but does not fully account for, the selectivity of these cells to HIV entry. GM-CSF, a cytokine that induces macrophage differentiation, caused a rapid decrease in CXCR4 and CCR5 mRNA and was correlated with decreased ability to support HIV entry.