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

Monocyte-derived macrophages and myeloid cell lines as targets of HIV-1 replication and persistence

HIV infection of mononuclear phagocytes (MP), mostly as tissue macrophages, is a dominant feature in the pathogenesis of HIV disease and its progression to AIDS. Although the general mechanism of infection is not dissimilar to that of CD4+ T lymphocytes occurring via interaction of the viral envelope with CD4 and a chemokine receptor (usually CCR5), other features are peculiar to MP infection. Among others, the long-term persistence of productive infection, sustained by the absence of substantial cell death, and the capacity of the virions to bud and accumulate in intracellular multivesicular bodies (MVB), has conferred to MP the role of "Trojan horses" perpetuating the chronic state of infection. Because the investigation of tissue macrophages is often very difficult for both ethical and practical reasons of accessibility, most studies of in vitro infection rely upon monocyte-derived macrophages (MDM), a methodology hampered by inter-patient variability and lack of uniformity of experimental protocols. A number of cell lines, mostly Mono Mac, THP-1, U937, HL-60, and their derivative chronically infected counterparts (such as U1 and OM-10.1 cell lines) have complemented the MDM system of infection providing useful information on the features of HIV replication in MP. This article describes and compares the most salient features of these different cellular models of MP infection by HIV.

SerpinB2 Is an Inducible Host Factor Involved in Enhancing HIV-1 Transcription and Replication

The serine protease inhibitor SerpinB2 (plasminogen activator inhibitor-2) is a major product of activated monocytes and macrophages and is substantially induced during most inflammatory processes. Distinct from its widely described extracellular role as an inhibitor of urokinase plasminogen activator, SerpinB2 has recently been shown to have an intracellular role as a retinoblastoma protein (Rb)-binding protein that inhibits Rb degradation. Here we show that HIV-1 infection and gp120 treatment of human peripheral blood mononuclear cells resulted in induction of SerpinB2. Furthermore, SerpinB2 expression in THP-1 monocyte/macrophage, Jurkat T, and HeLa cell lines increased replication of HIV-1 and enhanced transcription from the HIV-1 long terminal repeat (LTR) promoter by 3-10-fold. Increased HIV-1 gene expression and transcription was also observed in activated macrophages from SerpinB2+/+ mice compared with macrophages from SerpinB2-/- mice. The SerpinB2-mediated elevation of Rb protein levels appeared to be responsible for enhancing transcription from the core promoter region of the LTR by relieving HDM2-mediated inhibition of Sp1 and/or by increasing the Sp1/Sp3 expression ratios. This is the first report associating HIV-1 replication with SerpinB2 expression and illustrates that SerpinB2 is a potentially important inducible host factor that significantly promotes HIV-1 replication.

Interleukin-10 inhibits HIV-1 LTR-directed gene expression in human macrophages through the induction of cyclin T1 proteolysis

Regulation of HIV-1 replication in human monocytes/macrophages occurs at multiple levels including transcription of the proviral genome, which depends on virally encoded Tat protein. Interleukin-10 (IL-10), an anti-inflammatory cytokine which is up-regulated during disease progression of AIDS, has been reported to suppress HIV-1 replication in macrophages at a post-entry stage of the virus life cycle. Our previous studies have demonstrated that Tat function is regulated during the differentiation of monocyte-derived macrophages (MDMs) in a manner that correlates with the early induction and subsequent shut-off of its cellular cofactor cyclin T1. Here, we report that IL-10 down-regulates cyclin T1 expression through the induction of proteasome-mediated proteolysis in human macrophages. Using a reporter virus that is deficient in Tat function, we also demonstrate that IL-10 inhibits HIV-1 gene expression in a Tat-dependent manner. Together, these results suggest that the down-regulation of cyclin T1, and consequently Tat function, contributes to the suppressive effect of IL-10 on HIV-1 replication in human macrophages.

Therapy of "SHIV" infected macaques with liposomes delivering antisense interleukin-4 DNA

BACKGROUND/OBJECTIVES

To explore the effects of antisense (AS) interleukin (IL)-4 on virus replication and CD8+ T-cell responses in lymph nodes and blood of macaques infected with simian human immunodeficiency virus, SHIV(89.6)P.

METHODS

Six macaques were inoculated with simian human immunodeficiency virus (SHIV(89.6)P). Seven days later, four of the animals were given 1 mg AS IL-4 plasmid complexed with Megafectin liposome, intravenously, and two of these received a second injection of the same material on day 9. All six macaques were killed at 2 weeks post infection (pi) and monitored for viral RNA and CD8+ T cells in blood and lymph nodes by real-time reverse transcriptase-polymerase chain reaction, flow cytometry and immunohistochemistry.

RESULTS

In contrast to the lymph nodes from virus control animals, the lymph nodes of AS IL-4-treated animals had a significant reduction in viral loads and reduced depletion of cells from the nodes. There was an increase in CD8+ T cells in the nodes, and many of the cells expressed granzyme B, suggesting functional activation. This trend of virus reduction and increased CD8+ T cell numbers was also reflected in blood.

CONCLUSIONS

The therapeutic effect of the AS IL-4 suggests indirectly that the acute immunosuppressive disease caused by SHIVs is mediated, in part, by IL-4 that causes enhanced virus replication by suppressing anti-viral CD8+ T-cell responses, and that this effect was reduced by treatment of the animals with AS IL-4.

Macrophage activation and human immunodeficiency virus infection: HIV replication directs macrophages towards a pro-inflammatory phenotype while previous activation modulates macrophage susceptibility to infection and viral production

Macrophages are pivotal for the regulation of immune and inflammatory responses, but whether their role in HIV infection is protective or deleterious remains unclear. In this study, we investigated the effect of pro- and anti-inflammatory stimuli on macrophage sensitivity to two different aspects of HIV infection: their susceptibility to infection stricto sensu, which we measured by endpoint titration method, and their ability to support virus spread, which we measured by using an RT activity assay in infection kinetics. We show a partially protective role for pro-inflammatory agents as well as for IL-4. We also illustrate that various different stimuli display differential effects on macrophage susceptibility to HIV and on virus replication that occurs thereafter. On the other hand, HIV replication strongly repressed CD206 and CD163 expression, thus clearly orientating macrophages towards a pro-inflammatory phenotype, but independently of TNF. Taken together, our results emphasize that HIV infection of macrophages sets up inflammation at the cell level but through unexpected mechanisms. This may limit target susceptibility and participate in virus clearance but may also result in tissue damage.

Targeting melanocortin receptors as potential novel therapeutics

Adrenocorticotrophic hormone (ACTH(1-39)) and the melanocortins (alpha, beta and gamma-melanocyte-stimulating hormone [MSH]) are derived from a larger precursor molecule known as the pro-opiomelanocortin (POMC) protein. They exert their numerous biological effects by activating 7 transmembrane G-protein coupled receptors (GPCR), leading to adenylyl cyclase activation and subsequent cAMP accumulation within the target cell. To date, 5 melanocortin receptors (MCR) have been identified and termed MC1R to MC5R, they have been shown to have a wide and varied distribution throughout the body, being found in the central nervous system (CNS), periphery and immune cells. Melanocortins have a multitude of actions including: (i) modulating disease pathologies including arthritis, asthma, obesity; (ii) affecting functions, for example erectile dysfunction, skin tanning; and (iii) organ systems, for example cardiovascular system. Recently a mechanistic approach has been identified with alpha-MSH preventing NF-kappaB activation via the preservation and expression of IkappaBalphaprotein. This leads to a reduction of pro-inflammatory mediators including cytokines and inhibition of adhesion molecule expression, with subsequent reduction in leukocyte emigration. Development of selective ligands with an appropriate pharmacokinetic profile will enable a pharmacological evaluation of the potential beneficial effects of the melanocortins. In this review I have discussed the potential mechanistic action for the melanocortins and some of the disease pathologies shown to be modulated. This review proposes targeting the MCR with the ultimate aim of controlling many of the diseases that we face today.

Cell reservoirs in lymph nodes infected with HIV-1 subtype E differ from subtype B: identification by combined in situ polymerase chain reaction and immunohistochemistry

In Thailand, the predominant HIV subtype is E, rather than subtype B as in North America and Europe. Subtype E has the ability to replicate in vitro in Langerhans cells. We hypothesized that this cell type might constitute a reservoir for the HIV virus in infected lymph nodes. We examined lymph nodes from 25 HIV-1 subtype E-infected patients to determine the immunophenotype of HIV-1-infected cells, their numbers and their distribution. The presence of HIV was detected either by in situ reverse transcriptase-polymerase chain reaction or immunoperoxidase. Cell identity was determined by double labelling using alkaline phosphatase-based immunohistochemistry. The majority of HIV-infected cells in the lymph nodes were Langerhans cells (CD1a+S100+) and Langerhans-related dendritic cells (p55+S100+). These cells were located in the paracortical areas of lymph nodes, with a few cells scattered at the edges of germinal centers, but were absent from germinal centers themselves, in contrast to the reported distribution of subtype B virus. In addition, multinucleated giant cells were significantly more common in HIV-infected nodes (64%) compared to controls (4%) (P=0.00002). In conclusion, Langerhans histiocytes and related cells are reservoirs for HIV subtype E in lymph nodes. Disrupting the pathway of infection of Langerhans cells and related cells may be a viable strategy to interfere with transmission of HIV subtype E.

HIV-1 infection initiates changes in the expression of a wide array of genes in U937 promonocytes and HUT78 T cells

Human monocytes/macrophages (M/M) are the major targets for human immunodeficiency virus type 1 (HIV-1) infection. To characterize the global effects of acute HIV-1 infection on gene expression in M/M, the expression levels of 550 host cell RNA transcripts in U937 human promonocytes at 2-3 days after HIV-1 infection were assessed using cDNA microarray analysis and were compared to those in the infected HUT78, a CD4+ T cell line. Confirmed by semiquantitative RT-PCR, our results showed that 12 genes were up-regulated and 26 genes were down-regulated in the infected U937 cells at 2-3 days post-infection, whereas 8 genes were up-regulated and 20 genes were down-regulated in the infected HUT78 cells at 2-3 days post-infection. These genes encode a host of proteins with divergent functions in a variety of cellular processes including apoptosis (FAS, Fas ligand, PIN, HSP90beta, bcl-2, bcl-x), cell signal transduction (Ras, RGS1, IRF-1, STAT3), receptor-mediated signaling transduction (CD71, CD69, CD3delta), cell cycle and growth (c-myc, cytokines, kinase), transcriptional regulation (EWS, CREB-2), and chemotaxis (beta-chemokines, RANTES), supporting the general effects of HIV-1 infection on cells of different origin. Although most identified genes were regulated similarly in both infected cell lines, differences in gene regulation, such as c-myc, CD71, CD69, and beta-chemokines, between the two infected cell lines were also identified in this study. These differences may further our understanding of the pathogenicity of HIV and enable the discovery of novel therapeutic approach for AIDS.

Stage-specific effects of Plasmodium falciparum-derived hemozoin on blood mononuclear cell TNF-alpha regulation and viral replication

BACKGROUND

The molecular immunological interactions between HIV and malaria are largely undefined. Since tumor necrosis factor (TNF)-alpha is elevated during acute malaria and increases with HIV-1 disease progression, TNF-alpha production may be an important mediator for interactions between malaria and HIV-1.

METHODS

To examine the stage-specific immunological interactions between HIV and malaria, peripheral blood mononuclear cells (PBMC) and CD14 cells were isolated and cultured from rhesus macaques at different stages of SIV infection. Cultures were stimulated with lipopolysaccharide (LPS) and interferon (IFN)-gamma in the presence of Plasmodium falciparum-derived hemozoin (Hz) or synthetic Hz (sHz). TNF-alpha transcripts and soluble protein were examined by real time reverse transcription-PCR and ELISA, respectively. The effects of Hz on viral replication were determined by measurement of p27 antigen with varying concentrations of TNF-alpha neutralizing antibodies.

RESULTS

Hz and sHz significantly increased LPS- and IFN-gamma-induced TNF-alpha protein and transcripts in PBMC from animals with late stage SIV infection (i.e., AIDS). Hz and sHz also induced high levels of sustained TNF-alpha transcripts in PBMC from the AIDS group. During the late stage of disease, CD14 cells were the primary source of TNF-alpha production. Stimulation of PBMC with Hz and sHz significantly increased viral replication that was dose-dependently reduced by the addition of TNF-alpha neutralizing antibodies.

CONCLUSIONS

Hz promotes high levels of TNF-alpha production from PBMC during AIDS and increases viral replication in SIV-infected animals.

Uncoupling coreceptor usage of human immunodeficiency virus type 1 (HIV-1) from macrophage tropism reveals biological properties of CCR5-restricted HIV-1 isolates from patients with acquired immunodeficiency syndrome

The mechanisms underlying the pathogenicity of CCR5-restricted (R5) human immunodeficiency virus type-1 (HIV-1) strains are incompletely understood. Acquisition or enhancement of macrophage (M)-tropism by R5 viruses contributes to R5 HIV-1 pathogenesis. In this study, we show that M-tropic R5 viruses isolated from individuals with acquired immunodeficiency syndrome (late R5 viruses) require lower levels of CD4/CCR5 expression for entry, have decreased sensitivity to inhibition by the entry inhibitors TAK-779 and T-20, and have increased sensitivity to neutralization by the Env MAb IgG1b12 compared with non-M-tropic R5 viruses isolated from asymptomatic, immunocompetent individuals (early R5 viruses). Augmenting CCR5 expression levels on monocyte-derived macrophages via retroviral transduction led to a complete or marginal restoration of M-tropism by early R5 viruses, depending on the viral strain. Thus, reduced CD4/CCR5 dependence is a phenotype of R5 HIV-1 associated with M-tropism and late stage infection, which may affect the efficacy of HIV-1 entry inhibitors.

Involvement of IL-6 in the anti-human immunodeficiency virus activity of IFN-tau in human macrophages

IFN-tau is a non-cytotoxic type I IFN responsible for maternal recognition of the foetus in ruminants. IFN-tau has been found to inhibit HIV replication more strongly than human IFN-alpha, particularly in human monocyte-derived macrophages, without associated toxicity. Ovine IFN-tau uses the same anti-viral cellular pathways as human IFN-alpha in human macrophages, principally inhibiting the early steps of the biological cycle of HIV, preventing the integration of HIV DNA into the host-cell genome. In this study, we investigated the immunomodulatory properties of IFN-tau in human macrophages. We found that IFN-tau increased the production of IL-10 and IL-6, but not of IL-1beta or tumour necrosis factor alpha, in unstimulated, LPS-stimulated and HIV-1/Ba-L-infected macrophages. We also found that treatment with IL-6 inhibited HIV replication. Moreover, the neutralization of IL-6 activity in the cell culture supernatants of IFN-tau-treated macrophages led to a decrease in the anti-retroviral effects of IFN-tau, suggesting that IL-6 was involved in the anti-viral activity induced by IFN-tau. By focusing on the very early steps of the biological cycle of HIV, we showed that IL-6 co-operated with IFN-tau to decrease intracellular HIV RNA levels 2 h after infection.

Induction of 15-lipoxygenase-1 impairs expression of HIV-1 receptors CD4 and CXCR4 in monocytic cells

The lipoxygenase pathway of immunocompetent cells has been related to HIV infection and interleukins-4 and -13 have been described as major regulators of this metabolic route. To explore whether 15-lipoxygenase1 expression might impact the responsiveness of monocytic cells for HIV we induced expression of this enzyme by two independent ways (stable transfection of U937 cells and culturing of blood monocytes in vitro in the presence of granulocyte/monocyte colony stimulating factor and interleukin 4) and assayed the cellular content of the two HIV-1 receptors CD4 and CXCR4 (CD184) by real time RT-PCR and fluorescence-activated cell sorting. Wild-type U937 cells express CD4 and CXCR4 at high levels and expression was not altered when the cells were transfected with control plasmids. In contrast, expression of these proteins was strongly reduced when the cells were stably transfected with 15-lipoxygenase1. Similar effects were observed when blood monocytes were cultured in the presence of granulocyte/monocyte colony stimulating factor and interleukin-4. Under these conditions strong overexpression of 15-lipoxygenase1 was paralleled by downregulation of CD4 and CXCR4. Since these surface proteins are essential for the binding of T-tropic HIV-1 strains expression of 15-lipoxygenase1 may confer resistance against HIV infection to monocytic cells.

HIV-1 induces IL-10 production in human monocytes via a CD4-independent pathway

In HIV-infected patients, increased levels of IL-10, mainly produced by virally infected monocytes, were reported to be associated with impaired cell-mediated immune responses. In this study, we investigated how HIV-1 induces IL-10 production in human monocytes. We found that CD14(+) monocytes infected by either HIV-1(213) (X4) or HIV-1(BaL) (R5) produced IL-10, IL-6, tumor necrosis factor-alpha (TNF-alpha), and to a lesser extent, IFN-gamma. However, the capacity of HIV-1 to induce these cytokines was not dependent on virus replication since UV-inactivated HIV-1 induced similar levels of these cytokines. In addition, soluble HIV-1 gp160 could induce CD14(+) monocytes to produce IL-10 but at lower levels. Cross-linking CD4 molecules (XLCD4) with anti-CD4 mAbs and goat anti-mouse IgG (GAM) resulted in high levels of IL-6, TNF-alpha and IFN-gamma but no IL-10 production by CD14(+) monocytes. Interestingly, neither anti-CD4 mAbs nor recombinant soluble CD4 (sCD4) receptor could block IL-10 secretion induced by HIV-1(213), HIV-1(BaL) or HIV-1 gp160 in CD14(+) monocytes, whereas anti-CD4 mAb or sCD4 almost completely blocked the secretion of the other cytokines. Furthermore, HIV-1(213) could induce IL-10 mRNA expression in CD14(+) monocytes while XLCD4 by anti-CD4 mAb and GAM failed to do so. As with IL-10 protein levels, HIV-1(213)-induced IL-10 mRNA expression in CD14(+) monocytes could not be inhibited by anti-CD4 mAb or sCD4. Taken together, HIV-1 binding to CD14(+) monocytes can induce CD4-independent IL-10 production at both mRNA and protein levels. This finding suggests that HIV induces the immunosuppressive IL-10 production in monocytes and is not dependent on CD4 molecules and that interference with HIV entry through CD4 molecules may have no impact on counteracting the effects of IL-10 during HIV infection.

Immunomodulatory effects of the HIV-1 gp120 protein on antigen presenting cells: implications for AIDS pathogenesis

Antigen presenting cell (APC) function is central to the development of an effective anti-viral immune response. Among APC, monocytes, macrophages and dendritic cells (DC) form the principal non-T cell compartment involved in in vivo HIV infection, and these cells play important and well-established roles in multiple aspects of viral pathogenesis. HIV infection may result in APC defects, which could ultimately contribute to the loss of CD4+ T cell responses observed early in HIV infection, when the CD4+ T cell number is still within the normal range. Extensive in vitro studies have demonstrated that the envelope glycoproteins of HIV-1 exert profound influences on various cell populations of the immune system, including hematopoietic progenitors, T and B lymphocytes, monocytes/ macrophages and DC, as well as on neuronal cells. The demonstration of the presence of envelope proteins both free in the circulation and bound to the surface of CD4+ cells suggests that gp120 interactions with non-infected cells can influence cellular functions in vivo, thus contributing to the immunopathogenesis of AIDS. This paper provides an overview of the present knowledge on gp120 binding, signal transduction triggering and interference with macrophage and DC functions and it highlights the importance of this interaction in the pathogenesis of AIDS.

Transforming growth factor-beta1 increases CXCR4 expression, stromal-derived factor-1alpha-stimulated signalling and human immunodeficiency virus-1 entry in human monocyte-derived macrophages

Stromal-derived factor-1 (SDF-1/CXCL12) and its receptor CXCR4 play crucial roles in leukocyte migration and activation, as well as embryogenesis, angiogenesis, cancer and viral pathogenesis. CXCR4 is one of the major human immunodeficiency virus-1 (HIV-1) coreceptors on macrophages. In many tissues macrophages are one of the predominant cell types infected by HIV-1 and act as a reservoir for persistent infection and viral dissemination. In patients infected by HIV-1, blood and tissue levels of transforming growth factor-beta1 (TGF-beta1) are increased. The purpose of this study was to evaluate the effects of TGF-beta1 on CXCR4 expression and function in primary human monocyte-derived macrophages (MDMs) and rat microglia. TGF-beta1 up-regulated CXCR4 and enhanced SDF-1alpha-stimulated ERK1,2 phosphorylation in these cells. The increased CXCR4 expression in human MDMs resulted in increased susceptibility of the cells to entry by dual-tropic CXCR4-using HIV-1 (D-X4). In contrast, TGF-beta1 failed to increase CCR5 expression or infection by a CCR5-using virus in MDMs. Our data demonstrate that TGF-beta1 enhances macrophage responsiveness to SDF-1alpha stimulation and susceptibility to HIV-1 by selectively increasing expression of CXCR4. The results suggest that increased expression of CXCR4 on macrophages may contribute to the emergence of dual-tropic X4 viral variants at later stages of HIV-1 infection.

Investigations on four host response factors whose expression is enhanced in X4 SHIV encephalitis

HIV encephalopathy, one of the major complications of HIV infection, involves productive virus replication in macrophages in the brain in association with heightened expression of several host response factors. One or more of these factors are thought to be the cause of the degenerative changes in neurons in the brain. Macaques infected with SIV and SHIV viruses have provided excellent working models for studying mechanisms of the human disease. Although HIV encephalopathy is primarily associated with CCR5-utilizing viruses, our findings have shown that CXCR4-utilizing SHIVs were also capable of causing the syndrome in rhesus macaques. In SHIV-infected macaques, approximately 30% of the animals developed encephalitis. In order to understand the factors leading to end-stage encephalitis, we performed microarray analyses on brains of encephalitic and non-encephalitic-infected macaques, and found pronounced enhancement of expression of interleukin-4, platelet-derived growth factor-B chain, monocyte chemoattractant protein-1 and CXCL10 in the brains of the encephalitic animals. This review discusses the role of each of these factors in mediating SHIV encephalitis.

Role of cytokines and chemokines in the regulation of innate immunity and HIV infection

The earliest defense against microbial infection is represented by the responses of the innate (or natural) immune system, that also profoundly regulates the adaptive (or acquired) T- and B-cell immune responses. Activation of the innate immune system is primed by microbial invasion in response to conserved structures present in large groups of microorganisms (LPS, peptidoglycan, double-stranded RNA), and is finely tuned by different cell types (including dendritic cells, macrophages, natural killer cells, natural killer T cells, and gammadelta T cells). In addition, several soluble factors (complement components, defensins, mannose-binding lectins, interferons, cytokines and chemokines) can play a major role in the regulation of both the innate and adaptive immunity. In this review, we will briefly overview the regulation of some cellular subsets of the innate immune system particularly involved in human immunodeficiency virus (HIV) infection and then focus our attention on those cytokines and chemokines whose levels of expression are more profoundly affected by HIV infection and that, conversely, can modulate virus infection and replication.

Macrophages and HIV-1: dangerous liaisons

HIV-1, like the other lentiviruses, has evolved the ability to infect nondividing cells including macrophages. HIV-1 replication in monocytes/macrophages entails peculiar features and differs in many respects from that in CD4 T lymphocytes. HIV-1 exhibits different tropism for CD4 T cells and macrophages. The virus can enter macrophages via several routes. Mitosis is not required for nuclear import of viral DNA or for its integration into the host cell genome. Specific cellular factors are required for HIV-1 transcription in macrophages. The assembly and budding of viral particles in macrophages take place in late endosomal compartments. Viral particles can use the exosome pathway to exit cells. Given their functions in host defence against pathogens and the regulation of the immune response plus their permissivity to HIV-1 infection, monocytes/macrophages exert a dual role in HIV infection. They contribute to the establishment and persistence of HIV-1 infection, and may activate surrounding T cells favouring their infection. Furthermore, monocytes/macrophages act as a Trojan horse to transmit HIV-1 to the central nervous system. They also exhibit antiviral activity and express many molecules that inhibit HIV-1 replication. Activated microglia and macrophages may also exert a neurotrophic and neuroprotective effect on infected brain regulating glutamate metabolism or by secretion of neurotrophins. This review will discuss specific aspects of viral replication in monocytes/macrophages and the role of their interactions with the cellular environment in HIV-1 infection swinging between protection and pathogenesis.

Plasma interleukin-18 is associated with viral load and disease progression in HIV-1-infected patients

Recent studies demonstrate persistent elevation of interleukin-18 (IL-18) concentration in human immunodeficiency virus type 1 (HIV-1)-infected patients. Due to pleiotropic action of IL-18 on the immune system, dysregulation of its synthesis may lead to inappropriate immune activation. The aim of this study was to determine possible correlation between IL-18 levels and the natural stages of HIV-1 infection. IL-18 plasma concentrations were determined in 42 patients in different stages of an HIV-1 infection and in 15 healthy controls. HIV infection resulted in a more than fourfold increase of plasma IL-18 concentration compared to healthy individuals (865 +/- 87 vs. 206 +/- 32 pg/ml, P < 0.001). Moreover, a positive correlation between plasma IL-18 concentration and HIV viral load was found (r = 0.44, P < 0.01). Further analysis showed marked elevation of IL-18 levels in late-stage symptomatic patients. Plasma IL-18 concentrations in patients receiving high-activity antiretroviral treatment (HAART) were significantly lower than in those not undergoing antiretroviral treatment. Individuals who did not reach viral suppression showed higher IL-18 plasma concentration than the group with achieved viral suppression. Excessive production of IL-18 observed in our study may promote viral replication and disease progression in advanced, especially late-stage HIV-infected patients. Furthermore, reduction of IL-18 concentration can be an important step in HAART-related immune restoration.

Establishment of an ex vivo model of monocytes-derived macrophages differentiated from peripheral blood mononuclear cells (PBMCs) from HIV-1 transgenic rats

It has been developed an HIV type 1 transgenic rat model (HIV-1 Tg Rat) which contains a gag-pol-deleted HIV-1 provirus regulated by the viral LTR promoter. Although it harbors a non infectious provirus, efficient viral expression occurs in different tissues and disease manifestations as well as immune-response alterations and pathologies similar to humans can be observed. Regulation of HIV-1 expression is influenced by various cellular factors and it is well known that macrophages are one of the major reservoir of HIV-1 infection and a vehicle for virus spread to other tissues. Purpose of our work was to establish an antigen presenting cells (monocyte-derived macrophages, MDM) ex vivo model from these HIV-1 transgenic rats. This model can be used to study function of HIV-infected MDM and their behavior like HIV-1 reservoir. Ultimately, these studies may be helpful in defining approaches to control HIV-1 spread.

Human immunodeficiency virus type 1 protease inhibitors block toll-like receptor 2 (TLR2)- and TLR4-Induced NF-kappaB activation

Coinfections with opportunistic and pathogenic bacteria induce human immunodeficiency virus (HIV) replication through microbial antigen activation of NF-kappaB. Here, we assessed whether HIV type 1 protease inhibitors (PI) block microbial antigen activation of NF-kappaB. Human microvessel endothelial cells were transiently transfected with either endothelial cell-leukocyte adhesion molecule NF-kappaB luciferase or interleukin 6 (IL-6) promoter luciferase constructs by using FuGENE 6, and they were treated with PI (nelfinavir, ritonavir, or saquinavir) prior to stimulation with the Toll-like receptor 4 (TLR4) and TLR2 ligands, with lipopolysaccharide (LPS), soluble Mycobacterium tuberculosis factor, or Staphylococcus epidermidis phenol-soluble modulin, respectively, or with tumor necrosis factor alpha (TNF-alpha). Luciferase activity was measured by using a Promega luciferase kit. TNF-alpha release from the supernatant was measured by enzyme-linked immunosorbent assay. Cell death was assessed by lactate dehydrogenase assay. We observed that PI pretreatment blocked the TLR2- and TLR4- as well as the TNF-alpha-mediated NF-kappaB activation, in a dose-dependent manner. PI pretreatment also blocked the LPS-induced IL-6 promoter transactivation and TNF-alpha secretion. These data suggest that PI block HIV replication not only by inhibiting the HIV protease but also by blocking the TLR- and TNF-alpha-mediated NF-kappaB activation and proinflammatory cytokine production. These findings may help explain the immunomodulatory effects of PI, and they suggest an advantage for PI-containing drug regimens in the treatment of HIV-infected patients who are coinfected with opportunistic and pathogenic bacteria.

Inhibition of the human chemokine receptor CCR5 by variecolin and variecolol and isolation of four new variecolin analogues, emericolins A-D, from Emericella aurantiobrunnea

An extract from the fungus Emericella aurantiobrunnea was found to compete with macrophage inflammatory protein (MIP)-1alpha for binding to human CCR5 in a scintillation proximity assay (SPA). Bioassay-guided fractionation led to the isolation of variecolin (1) and variecolol (2), which had IC50 values of 9 and 32 microM, respectively. An X-ray crystal structure of variecolin (1) was obtained for the first time. Also isolated were four new inactive analogues, emericolin A (3), B (4), C (5), and D (6), and the relative stereochemistry of these compounds was determined by NMR methods using ROESY spectra and 1H/1H coupling constants.

Down-regulation of CXCR-4 and CCR-5 expression by interferon-gamma is associated with inhibition of chemotaxis and human immunodeficiency virus (HIV) replication but not HIV entry into human monocytes

Alterations in the expression of CXCR4 and CCR5, the co-receptors for HIV entry, may be associated with susceptibility of monocytic cells to HIV infection. Interferon (IFN)-gamma has been shown to inhibit HIV replication in monocytic cells, but the molecular mechanism involved is not well understood. To determine if IFN-gamma regulates HIV replication by altering CXCR-4/CCR-5 expression and hence virus entry into monocytic cells, we investigated the effects of IFN-gamma on CXCR-4 and CCR-5 expression and its biological implications with respect to HIV entry, replication and chemotaxis towards the CXCR-4 and CCR-5 ligands SDF-1 and MIP-1alpha, respectively. IFN-gamma decreased CXCR-4 and CCR-5 expression on monocytes derived from HIV-negative adults, HIV-positive adults and HIV-negative cord blood. This down-regulation of chemokine receptor expression did not result in a corresponding change in mRNA expression but was associated with elevated levels of the endogenously produced chemokines SDF-1 and RANTES. Furthermore, IFN-gamma inhibited chemotaxis in response to SDF-1 and MIP-1alpha, inhibited HIV replication, but failed to inhibit virus entry in monocytic cells. These results suggest that although IFN-gamma-induced down-regulation of CXCR-4 and CCR-5 expression is associated with an inhibition of SDF-1-/MIP-1alpha-mediated chemotaxis, IFN-gamma-induced inhibition of HIV replication may be mediated at levels subsequent to the virus entry.

Endosomes, exosomes and Trojan viruses

Retroviruses are enveloped viruses that are generally assumed to bud at the plasma membrane of infected cells. Recently it has become apparent that some of these viruses use the endocytic pathway to coordinate their assembly and release. In addition, these and some other enveloped viruses exploit the machinery that generates the internal membranes of multivesicular bodies (MVB). These observations and others have led to the suggestion that retroviruses be regarded as "viral exosomes". Here we discuss this concept and the emerging evidence that compartments of the endocytic pathway play important roles in the biogenesis of both the internal vesicles of MVB and viruses.

Characterization of two populations of human coronary artery endothelial cells1

BACKGROUND

Heterogeneity of endothelial cells may affect angiogenesis, vascular healing, and cardiovascular disease formation. The objective of this study was to identify and characterize populations of human coronary artery endothelial cells (HCAECs), their gene expression levels, and response to TNF-alpha stimulation.

MATERIALS AND METHODS

Commercial HCAECs were cultured with EGM-2 complete medium. Cell population was determined by flow cytometry analysis based on size-scatter distribution. Gene expression for each population with or without TNF-alpha (1 ng/ml) stimulation for 16 h was also studied by flow cytometry analysis with proper gating and fluorescence labeling of antibodies.

RESULTS

Two distinguished populations, HCAEC-I (small) and HCAEC-II (large), were identified through all passages (from 2 to 10) during cultures. Both HCAEC-I and HCAEC-II showed more than 90% positive staining for both von Willebrand factor and CD31 and were negative for CD34 and CD4 (less than 2%). HCAEC-I had substantially higher expression of cadherin-5 (71.91% versus 51.07%) than HCAEC-II. HCAEC-I also expressed much higher levels of vascular endothelial growth factor receptor-2 (VEGF-R2) (17.35% versus 0.77%), endothelial nitric oxide synthase (eNOS) (44.64% versus 2.54%), VCAM-1 (6.08% versus 1.18%), E-selectin (18.68% versus 1.42%), CXCR4 (61.05% versus 7.98%), and CCR5 (48.66% versus 1.97%) than HCAEC-II. HCAEC-II, however, had substantially higher expression of P1H12 (93.07% versus 58.73%) and ICAM-1 (94.37% versus 58.62%) than HCAEC-I. Following TNF-alpha stimulation, both populations substantially increased the expression of ICAM-1, VCAM-1, and E-selectin. HCAEC-I, however, had much higher expressions of VEGFR-2, eNOS, CXCR4, and CCR-5 than HACEC-II after TNF-alpha stimulation.

CONCLUSIONS

These data demonstrate that commercial HCAECs have two distinguished populations with different gene expression patterns and different responses following TNF-alpha stimulation. This study indicates that the heterogeneity of HCAECs may have biologic or pathologic significances in coronary arteries.

Avances en la inmunopatología de la infección por el VIH

The progressive and irreversible destruction of the immune system represents the hallmark of HIV infection. Even though this process is directly related to the infection of CD4 lymphocytes, the destruction of this lymphocyte population observed along infection is not solely due to a direct cytopathic effect elicited by HIV replication. AIDS immune pathogenesis is an extremely complex phenomenon involving different mechanisms which are not fully understood yet. In this article the mechanisms involved in HIV infection and destruction of target cells and the immune response elicited by HIV are analysed. Finally, viral escape mechanisms to host immune response are considered.

HIV-1 transmission and cytokine-induced expression of DC-SIGN in human monocyte-derived macrophages

Dendritic cell-specific intercellular adhesion molecule-3-grabbing nonintegrin (DC-SIGN) has been described as an attachment molecule for human immunodeficiency virus type 1 (HIV-1) with the potential to mediate its transmission. We examined DC-SIGN expression in monocyte-derived macrophages (MDM) and its role in viral transmission when MDM were exposed to interleukin (IL)-13, IL-4, or interferon-gamma (IFN-gamma). We show that IL-13 and IL-4 increase transcripts, total protein, and cell-surface expression of DC-SIGN in all MDM tested, IFN-gamma results ranged from no change to up-regulation of surface expression, and message and total protein were, respectively, induced in all and 86% of donors tested. Transmission experiments of HIV-1 X4 between cytokine-treated MDM to Sup-T1 cells showed no association between total transmission and DC-SIGN up-regulation. IL-4 but not IL-13 resulted in a less than twofold increase in MDM viral transmission to CD4+ T cells in spite of a fourfold up-regulation in DC-SIGN expression by either cytokine. In contrast, IFN-gamma treatment induced a decrease in total transmission by at least two-thirds, despite its induction of DC-SIGN. Soluble mannan resulted in a greater inhibition of viral transmission to CD4+ T cells than neutralizing anti-DC-SIGN monoclonal antibody (67-75% vs. 39-48%), supporting the role of mannose-binding receptors in viral transmission. Taken together, results show that DC-SIGN regulation in MDM does not singly predict the transmission potential of this cell type.

Phenolic derivatives from Wigandia urens with weak activity against the chemokine receptor CCR5

Three compounds, 2,3-dihydroxy-4-methoxy-6,6,9-trimethyl-6H-dibenzo[b,d]pyran (1), 8-methoxy-2-methyl-2-(4-methyl-3-pentenyl)-2H-1-benzopyran-6-ol (2) and 4-methoxy-3-(3-methyl-2-butenyl)-benzoic acid (3), have been isolated from Wigandia urens. The structures of compounds 1, 2 and 3 were determined from spectroscopic data and showed activity in a CCR5 assay with IC(50) values of 33, 46 and 26 muM respectively.

Macrophage activation through CCR5- and CXCR4-mediated gp120-elicited signaling pathways

Macrophages are major targets for infection by human immunodeficiency virus type 1 (HIV-1). In addition to their role as productive viral reservoirs, inappropriate activation of infected and uninfected macrophages appears to contribute to pathogenesis. HIV-1 infection requires initial interactions between the viral envelope surface glycoprotein gp120, the cell-surface protein CD4, and a chemokine receptor CCR5 or CXCR4. Besides their role in HIV-1 entry, CCR5 and CXCR4 are G protein-coupled receptors that can activate multiple intracellular signaling pathways. HIV-1 gp120 has been shown to activate signaling pathways through the chemokine receptors in several cell types including lymphocytes, neurons, and astrocytes. In some cell types, these consequences may cause cellular injury. In this review, we highlight our data demonstrating diverse signaling events that occur in primary human macrophages in response to gp120/chemokine receptor interactions. These responses include K+, Cl-, and nonselective cation currents, intracellular Ca2+ increases, and activation of several kinases including the focal adhesion-related tyrosine kinase Pyk2, mitogen-activated protein kinases (MAPK), and phosphoinositol-3 kinase. Activation of the MAPK leads to gp120-induced expression of chemokines such as monocyte chemoattractant protein-1 and macrophage-inflammatory protein-1beta and the proinflammatory cytokine tumor necrosis factor alpha. These responses establish a complex cytokine network, which may enhance or suppress HIV-1 replication. In addition, dysregulation of macrophage function by gp120/chemokine receptor signaling may contribute to local inflammation and injury and further recruit additional inflammatory and/or target cells. Targeting these cellular signaling pathways may have benefit in controlling inflammatory sequelae of HIV infection such as in neurological disease.

Infectious HIV-1 assembles in late endosomes in primary macrophages

Although human immunodeficiency virus type 1 (HIV-1) is generally thought to assemble at the plasma membrane of infected cells, virions have been observed in intracellular compartments in macrophages. Here, we investigated virus assembly in HIV-1-infected primary human monocyte-derived macrophages (MDM). Electron microscopy of cryosections showed virus particles, identified by their morphology and positive labeling with antibodies to the viral p17, p24, and envelope proteins, in intracellular vacuoles. Immunolabeling demonstrated that these compartments contained the late endosomal marker CD63, which was enriched on vesicles within these structures and incorporated into the envelope of budding virions. The virus-containing vacuoles were also labeled with antibodies against LAMP-1, CD81, and CD82, which were also incorporated into the viral envelope. To assess the cellular source of infectious viruses derived from MDM, virus-containing media from infected cells were precipitated with specific antibodies. Only antibodies against antigens found in late endosomes precipitated infectious virus, whereas antibodies against proteins located primarily on the cell surface did not. Our data indicate that most of the infectious HIV produced by primary macrophages is assembled on late endocytic membranes and acquires antigens characteristic of this compartment. This notion has significant implications for understanding the biology of HIV and its cell-cell transmission.

Interleukin-4 and interferon-gamma production during HIV-1 infection and changes induced by antiretroviral therapy

Several lines of evidence indicate that a switch of the cytokine pattern from a predominant type 1 (antiviral and cell mediated response) to type 2 (polyclonal humoral immune response) occurs during the course of Human Immunodeficiency Virus-1 (HIV-1) infection, and represents a key event in the progression of immunodeficiency and dysregulated immune activation. We proposed to further investigate this immunological aspect of HIV-1 disease, in naive and in patients treated with Highly Active Antiretroviral Therapy (HAART). The prototypic cytokines chosen were Interleukin (IL)-4 and Interferon-gamma (IFN-gamma), whose in vitro production was determined in mononuclear cell cultures stimulated with different T lymphocyte mitogenic agents (anti-CD3, Phytohaemoagglutin-P -PHA-, E. coli B04/035 Lipopolysaccharide -LPS-). We classified all the patients on the basis of the number of CD4+ lymphocytes and we found a progressive, even if not significant decrease in the baseline production of IFN-gamma with the progression of the immunodeficiency. The mean value of baseline IFN-gamma in the group of patients with CD4+>500 cells/microL was 7.79 +/- 3.1 pg/mL while in the group with CD4+<200 cells/microL it was 4.66 +/- 2.22. We didn't find significant differences in the baseline production of IL-4 in these groups and in IFN-gamma and IL-4 production in LPS-stimulated cultures. We also re-assessed 12 patients after one year's follow-up. They presented a significant increase in IFN-gamma production compared to the first assessment in the LPS-stimulated cultures (baseline IFN-gamma 2.87 +/- 1.17 pg/mL, after 12 months 19.15 +/- 5.19 pg/mL; p= 0.03). In the 12 patients in follow-up IL-4 production showed a decreased in PHA-stimulated cultures with mean values of 16.65 +/- 14.32 pg/mL at baseline and 6.54 +/- 6.54 pg/mL after follow-up. These results highlight the immunorestoring effects of HAART. IL-4 production was lower in the treated subjects compared to the naive ones in PHA-stimulated cultures (mean values: IL-4=13.42 +/- 11.08 pg/mL in the naive patients and 9.75 +/- 65 pg/mL in the treated patients). The IFN-gamma values in anti-CD3 stimulated cultures were also higher in the treated patients, but this increase was not significant.

Interleukin-10 induces the upregulation of the inhibitory receptor ILT4 in monocytes from HIV positive individuals

A characteristic of human immunodeficiency virus infected individuals is an impairment of immune responses, which can result in opportunistic infections. Elevated levels of interleukin-10 (IL-10), produced by virally infected monocytes, are found in the sera of HIV infected individuals. Such elevated levels have been associated with the impaired function of CD4(+) and CD8(+) T cells, and antigen presenting cells (APC), such as monocytes. IL-10 has been reported to upregulate the cell surface expression of the inhibitory receptors ILT3 and ILT4 on monocytes and dendritic cells. This study demonstrates that the decreased antigen presenting ability of monocytes in HIV(+) individuals is in part due to the upregulation of ILT4 on the monocytes caused by the elevated serum IL-10 levels seen in these individuals.