Interleukin 13 inhibits human immunodeficiency virus type 1 production in primary blood-derived human macrophages in vitro

A review of immune modulators and immunotherapy in infectious diseases

The human immune system responds to harmful foreign invaders frequently encountered by the body and employs defense mechanisms to counteract such assaults. Various exogenous and endogenous factors play a prominent role in maintaining the balanced functioning of the immune system, which can result in immune suppression or immune stimulation. With the advent of different immune-modulatory agents, immune responses can be modulated or regulated to control infections and other health effects. Literature provides evidence on various immunomodulators from different sources and their role in modulating immune responses. Due to the limited efficacy of current drugs and the rise in drug resistance, there is a growing need for new therapies for infectious diseases. In this review, we aim to provide a comprehensive overview of different immune-modulating agents and immune therapies specifically focused on viral infectious diseases.

CD8+ Lymphocytes from Healthy Blood Donors Secrete Antiviral Levels of Interferon-Alpha

The adaptive immune response to viral infections features the antigen-driven expansion of CD8+ T cells. These cells are widely recognized for their cytolytic activity that is mediated through the secretion of cytokines such as perforin and granzymes. Less appreciated is their ability to secrete soluble factors that restrict virus replication without killing the infected cells. In this study we measured the ability of primary anti-CD3/28-stimulated CD8+ T cells from healthy blood donors to secrete interferon-alpha. Supernatants collected from CD8+ T cell cultures were screened for their ability to suppress HIV-1 replication in vitro and their interferon-alpha concentrations were measured by ELISA. Interferon-alpha concentrations in the CD8+ T cell culture supernatants ranged from undetectable to 28.6 pg/mL. The anti-HIV-1 activity of the cell culture supernatants was observed to be dependent on the presence of interferon-alpha. Appreciable increases in the expression levels of type 1 interferon transcripts were observed following T cell receptor stimulation, suggesting that the secretion of interferon-alpha by CD8+ T cells is an antigen-driven response. In 42-plex cytokine assays, the cultures containing interferon-alpha were also found to contain elevated levels of GM-CSF, IL-10, IL-13, and TNF-alpha. Together, these results demonstrate that the secretion of anti-viral levels of interferon-alpha is a common function of CD8+ T cells. Furthermore, this CD8+ T cell function likely plays broader roles in health and disease.

Anti-HIV potency of T-cell responses elicited by dendritic cell therapeutic vaccination

Identification and characterization of CD8+ and CD4+ T-cell epitopes elicited by HIV therapeutic vaccination is key for elucidating the nature of protective cellular responses and mechanism of the immune evasion of HIV. Here, we report the characterization of HIV-specific T-cell responses in cART (combination antiretroviral therapy) treated HIV-1 infected patients after vaccination with ex vivo-generated IFNα Dendritic Cells (DCs) loaded with LIPO-5 (HIV-1 Nef 66-97, Nef 116-145, Gag 17-35, Gag 253-284 and Pol 325-355 lipopeptides). Vaccination induced and/or expanded HIV-specific CD8+ T cells producing IFNγ, perforin, granzyme A and granzyme B, and also CD4+ T cells secreting IFNγ, IL-2 and IL-13. These responses were directed against dominant and subdominant epitopes representing all vaccine regions; Gag, Pol and Nef. Interestingly, IL-2 and IL-13 produced by CD4+ T cells were negatively correlated with the peak of viral replication following analytic treatment interruption (ATI). Epitope mapping confirmed that vaccination elicited responses against predicted T-cell epitopes, but also allowed to identify a set of 8 new HIV-1 HLA-DR-restricted CD4+ T-cell epitopes. These results may help to better design future DC therapeutic vaccines and underscore the role of vaccine-elicited CD4+ T-cell responses to achieve control of HIV replication.

Dexamethasone Modulates IL-13 and IL-10 Expression

Interleukin (IL-)-10 and IL-13 are Th2-cell-associated cytokines with a variety of biologic activities in immune and inflammatory responses. It is known that glucocorticoids (GCs) modulate inflammatory and immune functions. In fact, GCs are involved to regulate the transcription of cytokines which are relevant in chronic inflammation and cell-mediated immune response.

In the present study we analyzed, in vitro, the effects of DEX on the expression of the IL-10 and IL-13 lymphokines in murine spleen and thymus cells. DEX-stimulation induced down-regulation of the expression of IL-10 and IL-13 mRNA.

This effect was already evident 0.5 hr after treatment and persisted in time, in both resting and activated lymphocytes. These results suggest that GCs could have inhibitory effect on Th2 cytokine production.

Evaluation of somatic embryos of alfalfa for recombinant protein expression

Somatic embryos of alfalfa can accumulate higher levels of recombinant proteins comparing to vegetative organs. Somatic embryos may be explored as a new system for new protein production for plants. Plants have been explored via genetic engineering as an inexpensive system for recombinant protein production. However, protein expression levels in vegetative tissues have been low, which limits the commercial utilization of plant expression systems. Somatic embryos resemble zygotic embryos in many aspects and may accumulate higher levels of proteins as true seed. In this study, somatic embryo of alfalfa (Medicago sativa L.) was investigated for the expression of recombinant proteins. Three heterologous genes, including the standard scientific reporter uid that codes for β-glucuronidase and two genes of interest: ctb coding for cholera toxin B subunit (CTB), and hIL-13 coding for human interleukin 13, were independently introduced into alfalfa via Agrobacterium-mediated transformation. Somatic embryos were subsequently induced from transgenic plants carrying these genes. Somatic embryos accumulated approximately twofold more recombinant proteins than vegetative organs including roots, stems, and leaves. The recombinant proteins of CTB and hIL-13 accumulated up to 0.15 and 0.18 % of total soluble protein in alfalfa somatic embryos, respectively. The recombinant proteins expressed in somatic embryos also exhibited biological activities. As somatic embryos can be induced in many plant species and their production can be scaled up via different avenues, somatic embryos may be developed as an efficient expression system for recombinant protein production.

Modulation of gut-specific mechanisms by chronic δ(9)-tetrahydrocannabinol administration in male rhesus macaques infected with simian immunodeficiency virus: a systems biology analysis

Our studies have demonstrated that chronic Δ(9)-tetrahydrocannabinol (THC) administration results in a generalized attenuation of viral load and tissue inflammation in simian immunodeficiency virus (SIV)-infected male rhesus macaques. Gut-associated lymphoid tissue is an important site for HIV replication and inflammation that can impact disease progression. We used a systems approach to examine the duodenal immune environment in 4- to 6-year-old male rhesus monkeys inoculated intravenously with SIVMAC251 after 17 months of chronic THC administration (0.18-0.32 mg/kg, intramuscularly, twice daily). Duodenal tissue samples excised from chronic THC- (N=4) and vehicle (VEH)-treated (N=4) subjects at ∼5 months postinoculation showed lower viral load, increased duodenal integrin beta 7(+)(β7) CD4(+) and CD8(+) central memory T cells, and a significant preferential increase in Th2 cytokine expression. Gene array analysis identified six genes that were differentially expressed in intestinal samples of the THC/SIV animals when compared to those differentially expressed between VEH/SIV and uninfected controls. These genes were identified as having significant participation in (1) apoptosis, (2) cell survival, proliferation, and morphogenesis, and (3) energy and substrate metabolic processes. Additional analysis comparing the duodenal gene expression in THC/SIV vs. VEH/SIV animals identified 93 differentially expressed genes that participate in processes involved in muscle contraction, protein folding, cytoskeleton remodeling, cell adhesion, and cell signaling. Immunohistochemical staining showed attenuated apoptosis in epithelial crypt cells of THC/SIV subjects. Our results indicate that chronic THC administration modulated duodenal T cell populations, favored a pro-Th2 cytokine balance, and decreased intestinal apoptosis. These findings reveal novel mechanisms that may potentially contribute to cannabinoid-mediated disease modulation.

Effect of helminth-induced immunity on infections with microbial pathogens

Helminth infections are ubiquitous worldwide and can trigger potent immune responses that differ from and potentially antagonize host protective responses to microbial pathogens. In this Review we focus on the three main killers in infectious disease-AIDS, tuberculosis and malaria-and critically assesses whether helminths adversely influence host control of these diseases. We also discuss emerging concepts for how M2 macrophages and helminth-modulated dendritic cells can potentially influence the protective immune response to concurrent infections. Finally, we present evidence advocating for more efforts to determine how and to what extent helminths interfere with the successful control of specific concurrent coinfections.

Mucosal and peripheral Lin- HLA-DR+ CD11c/123- CD13+ CD14- mononuclear cells are preferentially infected during acute simian immunodeficiency virus infection

Massive infection of memory CD4 T cells is a hallmark of early simian immunodeficiency virus (SIV) infection, with viral infection peaking at day 10 postinfection (p.i.), when a majority of memory CD4 T cells in mucosal and peripheral tissues are infected. It is not clear if mononuclear cells from the monocyte and macrophage lineages are similarly infected during this early phase of explosive HIV and SIV infections. Here we show that, at day 10 p.i., Lin(-) HLA-DR(+) CD11c/123(-) CD13(+) CD14(-) macrophages in the jejunal mucosa were infected, albeit at lower levels than CD4 memory T cells. Interestingly, Lin(-) HLA-DR(+) CD11c/123(-) CD13(+) CD14(-) macrophages in peripheral blood, like their mucosal counterparts, were preferentially infected compared to Lin(-) HLA-DR(+) CD11c/123(-) CD13(+) CD14(+) monocytes, suggesting that differentiated macrophages were selectively infected by SIV. CD13(+) CD14(-) macrophages expressed low levels of CD4 compared to CD4 T cells but expressed similar levels of CCR5 as lymphocytes. Interestingly, CD13(+) CD14(-) macrophages expressed Apobec3G at lower levels than CD13(+) CD14(+) monocytes, suggesting that intracellular restriction may contribute to the differential infection of mononuclear subsets. Taken together, our results suggest that CD13(+) CD14(-) macrophages in mucosal and peripheral tissues are preferentially infected very early during the course of SIV infection.

Responsiveness of HIV-specific CD4 T cells to PD-1 blockade

Defining the T helper functions impaired by programmed death-1 (PD-1) is crucial for understanding its role in defective HIV control and determining the therapeutic potential of targeting this inhibitory pathway. We describe here the relationships among disease stage, levels of PD-1 expression, and reversibility of CD4 T-cell impairment. PD-L1 blockade in vitro enhanced HIV-specific production of Th0 (IL-2), Th1 (IFN-γ), Th2 (IL-13), and TFH (IL-21) cytokines by CD4 T cells. PD-L1 blockade caused an early increase in cytokine transcription and translation that preceded cell proliferation. Although the impact of PD-L1 blockade on cytokine expression and, to a lesser extent, cell proliferation was associated with markers of disease progression, restoration of cytokine secretion was also observed in most subjects with undetectable viremia. PD-L1 blockade restored cytokine secretion in both PD-1intermediate and PD-1high sorted CD4 T-cell subsets. Compared with PD-1high HIV-specific CD8 T cells, PD-1high HIV-specific CD4 T cells showed lower expression of the inhibitory molecules CD160 and 2B4, demonstrating marked differences in expression of inhibitory receptors between T-cell subsets. These data show that PD-1 impairs HIV-specific T helper responses both by limiting expansion of these cells and by inhibiting effector functions of multiple differentiated CD4 T-cell subsets.

The macrophage in HIV-1 infection: from activation to deactivation?

Macrophages play a crucial role in innate and adaptative immunity in response to microorganisms and are an important cellular target during HIV-1 infection. Recently, the heterogeneity of the macrophage population has been highlighted. Classically activated or type 1 macrophages (M1) induced in particular by IFN-γ display a pro-inflammatory profile. The alternatively activated or type 2 macrophages (M2) induced by Th-2 cytokines, such as IL-4 and IL-13 express anti-inflammatory and tissue repair properties. Finally IL-10 has been described as the prototypic cytokine involved in the deactivation of macrophages (dM). Since the capacity of macrophages to support productive HIV-1 infection is known to be modulated by cytokines, this review shows how modulation of macrophage activation by cytokines impacts the capacity to support productive HIV-1 infection. Based on the activation status of macrophages we propose a model starting with M1 classically activated macrophages with accelerated formation of viral reservoirs in a context of Th1 and proinflammatory cytokines. Then IL-4/IL-13 alternatively activated M2 macrophages will enter into the game that will stop the expansion of the HIV-1 reservoir. Finally IL-10 deactivation of macrophages will lead to immune failure observed at the very late stages of the HIV-1 disease.

A novel platform for biologically active recombinant human interleukin-13 production

Interleukin-13 (IL-13) is a pleiotropic regulatory cytokine with the potential for treating several human diseases, including type-1 diabetes. Thus far, conventional expression systems for recombinant IL-13 production have proven difficult and are limited by efficiency. In this study, transgenic plants were used as a novel expression platform for the production of human IL-13 (hIL-13). DNA constructs containing hIL-13 cDNA were introduced into tobacco plants. Transcriptional expression of the hIL-13 gene in transgenic plants was confirmed by reverse transcriptase-polymerase chain reaction and Northern blotting. Western blot analysis showed that the hIL-13 protein was efficiently accumulated in transgenic plants and present in multiple molecular forms, with an expression level as high as 0.15% of total soluble protein in leaves. The multiple forms of plant-derived recombinant hIL-13 (rhIL-13) are a result of differential N-linked glycosylation, as revealed by enzymatic and chemical deglycosylation, but not of disulphide-linked oligomerization. In vitro trypsin digestion indicated that plant rhIL-13 was more resistant than unglycosylated control rhIL-13 to proteolysis. The stability of plant rhIL-13 to digestion was further supported with simulated gastric and intestinal fluid digestion. In vitro bioassays using a factor-dependent human erythroleukaemic cell line (TF-1 cells) showed that plant rhIL-13 retained the biological functions of the authentic hIL-13 protein. These results demonstrate that transgenic plants are superior to conventional cell-based expression systems for the production of rhIL-13. Moreover, transgenic plants synthesizing high levels of rhIL-13 may prove to be an attractive delivery system for direct oral administration of IL-13 in the treatment of clinical diseases such as type-1 diabetes.

IL-13 is associated with reduced illness and replication in primary respiratory syncytial virus infection in the mouse

The role of IL-13 in respiratory syncytial virus (RSV) immunopathogenesis is incompletely described. To assess the effect of IL-13 on primary RSV infection, transgenic mice which either overexpress IL-13 in the lung (IL-13 OE) or non-transgenic littermates (IL-13 NT) were challenged intranasally with RSV. IL-13 OE mice had significantly decreased peak viral titers four days after infection compared to non-transgenic littermates. In addition, IL-13 OE mice had significantly lower RSV-induced weight loss and reduced lung IFN-γ protein expression compared with IL-13 NT mice. In contrast, primary RSV challenge of IL-13 deficient mice resulted in a small, but statistically significant increase in viral titers on day four after infection, no difference in RSV-induced weight loss compared to wild type mice, and augmented IFN-γ production on day 6 after infection. In STAT1-deficient (STAT1 KO) mice, where primary RSV challenge produced high levels of IL-13 production in the lungs, treatment with an IL-13 neutralizing protein resulted in greater peak viral titers both four and six days after RSV and greater RSV-induced weight loss compared to mice treated with a control protein. These results suggest that IL-13 modulates illness from RSV-infection.

A cell-based high-throughput assay for screening inhibitors of human papillomavirus-16 long control region activity

Cervical carcinomas express human papillomavirus (HPV) E6 and E7 oncoproteins, which are required to maintain the proliferative state of cancer cells. Repression of E6 and E7 expression results in acquisition of senescent phenotype and in the rescue of functional p53 and p105(Rb) pathways; therefore, therapies directed against either viral protein may be beneficial. However, the systems to study HPV in vitro are technically difficult and not convenient for screening of antiviral compounds. This has hampered the discovery of drugs against HPV. Here we describe the generation and use of a high-throughput screening system based on keratinocytes stably transfected with a reporter construct containing the regulatory sequence of E6 and E7 gene transcription (LCR) that allows easy detection of inhibitors of E6 and E7 expression in libraries of synthetic or biological compounds. The assay was used to screen a wide panel of cytokines: among them, IL-4, IL-13, TGF-beta1, TGF-beta2, TGF-beta3, TNF-alpha, IFN-alpha, and IFN-beta were found to induce a strong inhibition of the LCR activity. Our assay provides a validated tool in the search for drugs against HPV-associated cervical carcinomas and allowed the first systematic analysis of the effect of cytokines on the HPV-16 LCR transcriptional activity.

IL-13 Acutely Augments HIV-Specific and Recall Responses from HIV-1-Infected Subjects In Vitro by Modulating Monocytes

We show in this study that acute exposure of PBMCs derived from HIV-infected subjects to IL-13 results in increased recall T cell lymphoproliferative responses against HIV-1 p24 (n = 30, p < 0.0001) and other recall Ags (influenza, n = 43, p < 0.0001; purified protein derivative tuberculin, n = 6, p = 0.0299). This effect is due to a mechanism that acutely targets APC function in the adherent monocyte subset, as shown by the expansion of CD4(+) T cell responses following coculture of IL-13-treated enriched CD14(+) monocytes with donor-matched enriched CD4(+) T cells and Ag. Exposure to IL-13 over 18-72 h resulted in a significant enhancement of monocyte endocytosis (n = 11, p = 0.0005), CD86 expression (n = 12, p = 0.001), and a significant decrease in spontaneous apoptosis (n = 8, p = 0.008). Moreover, IL-13 exposure induced a significant decrease of significantly elevated constitutive levels of PBMC-secreted TNF-alpha (n = 14, p < 0.001) and IL-10 (n = 29, p < 0.001) within 18 h of exposure ex vivo, also reflected by decreased gene expression in the adherent cell population. Our data show that IL-13 is able to acutely enhance the function of the CD14(+) cell subset toward supporting Ag-specific cell-mediated responses in chronic HIV-1 infection.

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.

Lack of persistent drug-resistant mutations evaluated within and between treatment interruptions in chronically HIV-1-infected patients

OBJECTIVE

To determine the effect of treatment interruptions (TI) on the evolution and persistence of drug-resistant viruses in chronically HIV-1-infected suppressed patients.

METHODS

The emergence of viral resistance to combination antiretroviral therapy was monitored in 11 suppressed chronically HIV-1-infected patients undergoing from one up to four sequential TI (a total of 25 TI), by genotyping of the virus for known mutations in the genes for protease and reverse transcriptase. Resistance assays were performed at the first viral rebound > 100 copies/ml.

RESULTS

All subjects achieved resuppression of HIV-1 under the same antiretroviral therapy, regardless of the number of TI. Five of eleven patients showed no development of resistance. In the remaining six patients, the following patterns of mutations associated with viral resistance were found: one mutation (K70R), which was observed in one patient during the 1st TI and persisted during follow-up; two mutations (L90M, M184V), which were observed in four patients during the 1st TI and were intermittently present or lost following extended TI, treatment reinitiation and/or during subsequent TI; and evolution of two mutations (M184V, K219E) observed in two patients. These two mutations were not present during the 1st TI and were subsequently lost following therapy reinitiation or during the next TI.

CONCLUSIONS

Detection of drug resistance during TI by virus genotyping assays does not predict failure to resuppress after antiretroviral therapy reinitiation nor persistence of a resistant viral population during extended interruptions or subsequent TI.

Fcgamma receptor-mediated suppression of human immunodeficiency virus type 1 replication in primary human macrophages

Permissiveness of monocytes and macrophages to human immunodeficiency virus (HIV) infection is modulated by various stimuli. In this study we demonstrate that stimulation of primary monocytes and monocyte-derived macrophages (MDM) through the receptors for the Fc portion of immunoglobulin G (IgG) (FcgammaR) inhibits HIV type 1 (HIV-1) replication. Viral p24 production was decreased by 1.5 to 3 log units in MDM infected with both R5 and X4 HIV-1 strains upon stimulation by immobilized IgG but not upon stimulation by soluble IgG or by F(ab')(2) IgG fragments. Although MDM activation by immobilized IgG induced high levels of macrophage-derived chemokine secretion as well as a sustained down-regulation of CD4 and a transient decrease in CCR5 expression, these factors did not appear to play a major role in the suppression of HIV-1 replication. Single-cycle infection of FcgammaR-stimulated MDM with HIV-1 virions pseudotyped with either HIV-1 R5 or vesicular stomatitis virus G envelopes was inhibited, suggesting a postentry restriction of viral replication. PCR analyses of HIV-1 DNA intermediate replication forms suggested that reverse transcription is not affected by stimulation with immobilized human IgG, at least during the first replication cycle. The accumulation of PCR products corresponding to nuclear unintegrated two-long-terminal-repeat circles and the relative decrease of integrated HIV-1 DNA signals suggest an inhibition of proviral integration. Our data, showing that FcgammaR-mediated activation of MDM is a potent mechanism of HIV-1 suppression, raise the possibility that FcgammaR cross-linking by immune complexes may contribute to the control of viral replication in macrophages.

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.

Interleukin (IL)-4 inhibits phorbol-ester induced HIV-1 expression in chronically infected U1 cells independently from the autocrine effect of endogenous tumour necrosis factor-alpha, IL-1beta, and IL-1 receptor antagonist

The anti-inflammatory cytokine interleukin 4 (IL-4) has shown both inductive and inhibitory effects on the replication of the human immunodeficiency virus type 1 (HIV-1) in primary CD4+ T cells and mononuclear phagocytes. In this study, IL-4 did not induce virus production, but inhibited phorbol esters (PMA)-stimulated HIV expression in chronically infected promonocytic U1 cells. This effect, however, was not accounted for by a decreased secretion of endogenous TNF-alpha induced by phorbol myristate acetate (PMA). We also observed that PMA upregulated the production of both IL-1beta and of IL-1 receptor antagonist (IL-1ra). IL-4 inhibited the secretion of IL-1beta and strongly increased that of IL-1ra; however, these effects were not responsible of IL-4-mediated inhibition of PMA-induced HIV expression since anti-IL-1ra antibodies did not revert IL-4 mediated suppression. U1 cells were transiently transfected with both wild-type (WT) long terminal repeat (LTR) constructs, or with LTR plasmids containing deletions of either the NF-kappaB or the Sp-1 binding sites. IL-4 inhibited LTR-driven transcription triggered by PMA stimulation of U1 cells, and this effect was dependent upon intact NF-kappaB but not Sp-1 binding sites. Thus, IL-4 may favour a state of microbiological quiescence in infected monocytic cells bypassing the induction of HIV expression mediated by pro-inflammatory cytokines.

Activation by 9-(R)-[2-(phosphonomethoxy)propyl]adenine of chemokine (RANTES, macrophage inflammatory protein 1alpha) and cytokine (tumor necrosis factor alpha, interleukin-10 [IL-10], IL-1beta) production

Development of a novel group of antiviral agents, acyclic nucleoside phosphonates, has provided a new perspective for treating human immunodeficiency virus (HIV) infection. One of the compounds, 9-(R)-[2-(phosphonomethoxy)propyl]adenine (PMPA) (tenofovir), has been shown to confer complete protection against AIDS in a simian model of the infection. The aim of our study was to investigate whether the antiviral efficacy of PMPA, which depends mainly on inhibition of virus-induced DNA polymerase or of reverse transcriptase, could be contributed by immunomodulatory potential of this drug. We screened for its ability to activate production of cytokines and chemokines that are known to interfere with the replication and/or the entry of HIV in cells. Using the in vitro test system of mouse macrophages and lymphocytes, it has been found that PMPA stimulates macrophage secretion of interleukin-1beta (IL-1beta), IL-10, and tumor necrosis factor alpha. Production of the chemokines RANTES and macrophage inflammatory protein 1alpha was activated in both macrophages and lymphocytes, and also in human cell line U937. Other cytokines--i.e., IL-2, IL-12, IL-13, and gamma interferon-remained uninfluenced by PMPA. The cytokines were stimulated in a dose-dependent fashion, with rapid onset, and peak concentrations were achieved within 5 to 24 h. The findings contribute to a more complex understanding of mechanisms of antiviral effectiveness of PMPA and support the view that this drug could become a promising candidate for therapeutic exploitation in anti-HIV preventive medicine.

CCR5 and CXCR4 expression correlated with X4 and R5 HIV-1 infection yet not sustained replication in Th1 and Th2 cells

OBJECTIVE

To investigate the infectivity of T-helper (Th)1 and Th2 cells (derived from ccr5 wild-type and homozygous ccr5 Delta 32) to R5 and X4 HIV-1.

DESIGN

It remains unclear whether infection of Th1 and Th2 CD4 cells by R5 and X4 viruses mirrors their co-receptor expression profile as no direct quantitation of coreceptor levels and infection has been performed. In addition, it is unknown whether the lack of CCR5 expression affects the degree of Th1/Th2 polarization.

METHODS

Surface expression of CCR5 and CXCR4 was determined by quantitative fluorescence activated cell sorter analysis on in vitro differentiated Th1 and Th2 cells. R5 (Ba-L) and X4 (IIIB) HIV-1 isolates were used for infection studies and the efficiency of viral entry was determined by quantitative real time polymerase chain reaction detection of reverse transcribed proviral DNA.

RESULTS

Cell surface density of CCR5 molecules was eight-fold higher in Th1 versus Th2 subsets (P = 0.005) whereas CXCR4 surface density was four-fold higher in Th2 versus Th1 subsets (P = 0.006). Preferential infection and entry of Th1 cells by R5 HIV-1 was not associated with preferential replication, as eventually the R5-virus replicated to a higher level in Th2 cells in spite of lower initial viral infection/entry. By contrast, Th2 cells preferentially supported X4-virus infection and replication. High beta chemokine secretion by Th1 cells was associated with a lower R5 replication rate.

CONCLUSIONS

Th1 and Th2 cells differ in their infection efficiency for R5 and X4 HIV-1. ccr5 Delta 32-homozygous individuals maintain the ability for Th1/Th2 polarization, i.e., the expression of CCR5 is not required for Th1/Th2 polarization.

Noncytolytic inhibition of X4 virus by bulk CD8(+) cells from human immunodeficiency virus type 1 (HIV-1)-infected persons and HIV-1-specific cytotoxic T lymphocytes is not mediated by beta-chemokines

Human immunodeficiency virus (HIV)-specific cytotoxic T lymphocytes (CTL) mediate immunologic selection pressure by both cytolytic and noncytolytic mechanisms. Non cytolytic mechanisms include the release of beta-chemokines blocking entry of R5 HIV-1 strains. In addition, CD8(+) cells inhibit X4 virus isolates via release of as yet poorly characterized soluble factors. To further characterize these factors, we performed detailed analysis of CTL as well as bulk CD8(+) T lymphocytes from six HIV-1-infected individuals and from six HIV-1-seronegative individuals. Kinetic studies revealed that secreted suppressive activities of HIV-1-specific CTL and bulk CD8(+) T lymphocytes from all HIV-1-infected persons are significantly higher than that of supernatants from seronegative controls. The suppressive activity could be blocked by monensin and brefeldin A, was heat labile, and appeared in a pattern different from that of secretion of chemokines (MDC, I-309, MIP-1alpha, MIP-1beta, and RANTES), cytokines (gamma interferon, tumor necrosis factor alpha, and granulocyte-macrophage colony-stimulating factor), and interleukins (interleukin-13 and interleukin-16). This suppression activity was characterized by molecular size exclusion centrifugation and involves a suppressive activity of >50 kDa which could be bound to heparin and a nonbinding inhibitory activity of <50 kDa. Our data provide a functional link between CD8(+) cells and CTL in the noncytolytic inhibition of HIV-1 and suggest that suppression of X4 virus is mediated through proteins. The sizes of the proteins, their affinity for heparin, and the pattern of release indicate that these molecules are not chemokines.

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.

Interleukin-13 fusion cytotoxin as a potent targeted agent for AIDS-Kaposi's sarcoma xenograft

Clinically advanced and rapidly progressive AIDS-associated Kaposi sarcoma (AIDS-KS) tumors require an aggressive tumor-directed therapy. We have observed that AIDS-KS cells express high levels of receptors for immune regulatory cytokine, interleukin-13 (IL-13). Two tumorigenic AIDS-KS cell lines, KS Y-1 and KS-imm, expressed 4560 and 9480 IL-13 binding sites per cell with an affinity (kd) of ∼0.9 and 3.7 nmol/L, respectively. IL-13 cytotoxin IL13-PE38QQR, consisting of human IL-13 and a derivative of Pseudomonas exotoxin, is specifically cytotoxic to KS tumor cells. Systemic and loco regional administration of IL13-PE38QQR in immunodeficient mice with established human KS tumors produced remarkable antitumor activity. Three intratumoral (IT) injections of IL-13 toxin (250 μg/kg per dose) on alternate days (qod) or 5 daily (qd) IT injections with lower doses (50 or 100 μg/kg per dose) resulted in a complete regression of established subcutaneous tumors in most animals. Daily IT treatment with 250 μg/kg of IL-13 toxin in another KS-derived cell line also produced complete responses. Twice daily intraperitoneal injections of IL13-PE38QQR (25 or 50 μg/kg per dose) for 10 days (total injections = 20) also completely eradicated KS Y-1 tumors. Intravenous administration of IL13-PE38QQR also suppressed tumor growth; however, complete responses were not observed. All animals tolerated the therapeutic doses of IL-13 toxin without any visible signs of toxicity. The efficacy of receptor-directed IL13-PE38QQR therapy in mice warrants further exploration of this drug for AIDS-KS treatment.

Interleukin-13 fusion cytotoxin as a potent targeted agent for AIDS-Kaposi's sarcoma xenograft

Clinically advanced and rapidly progressive AIDS-associated Kaposi sarcoma (AIDS-KS) tumors require an aggressive tumor-directed therapy. We have observed that AIDS-KS cells express high levels of receptors for immune regulatory cytokine, interleukin-13 (IL-13). Two tumorigenic AIDS-KS cell lines, KS Y-1 and KS-imm, expressed 4560 and 9480 IL-13 binding sites per cell with an affinity (kd) of ∼0.9 and 3.7 nmol/L, respectively. IL-13 cytotoxin IL13-PE38QQR, consisting of human IL-13 and a derivative of Pseudomonas exotoxin, is specifically cytotoxic to KS tumor cells. Systemic and loco regional administration of IL13-PE38QQR in immunodeficient mice with established human KS tumors produced remarkable antitumor activity. Three intratumoral (IT) injections of IL-13 toxin (250 μg/kg per dose) on alternate days (qod) or 5 daily (qd) IT injections with lower doses (50 or 100 μg/kg per dose) resulted in a complete regression of established subcutaneous tumors in most animals. Daily IT treatment with 250 μg/kg of IL-13 toxin in another KS-derived cell line also produced complete responses. Twice daily intraperitoneal injections of IL13-PE38QQR (25 or 50 μg/kg per dose) for 10 days (total injections = 20) also completely eradicated KS Y-1 tumors. Intravenous administration of IL13-PE38QQR also suppressed tumor growth; however, complete responses were not observed. All animals tolerated the therapeutic doses of IL-13 toxin without any visible signs of toxicity. The efficacy of receptor-directed IL13-PE38QQR therapy in mice warrants further exploration of this drug for AIDS-KS treatment.

Laureate ESCI award for excellence in clinical science 1999. Cytokines and the human immunodeficiency virus: from bench to bedside. European Society for Clinical Investigation

Replication of the human immunodeficiency virus (HIV), the causative agent of the acquired immunodeficiency syndrome (AIDS), is under the control of both viral and host factors. Among the latter, the regulatory network of cytokines has been shown to affect virtually every step of the virus life cycle, from cell entry to budding of new progeny virions. Proinflammatory cytokines, such as tumour necrosis factor alpha, can either trigger or potentiate HIV expression via activation of the cellular transcription factor NF-kappaB. Other molecules, including interleukin 6 (IL-6) and the interferons, can up-regulate HIV expression by acting predominantly at post-transcriptional and/or post-translational levels. Anti-inflammatory cytokines, including transforming growth factor beta, IL-4 and IL-10, counteract these effects but can also potentiate viral replication under different experimental conditions. Chemotactic cytokines (chemokines) have recently entered the arena of host factors controlling viral spreading as potent inhibitors competing with the virus for cell-surface 7-transmembrane domain receptors also acting, together with CD4, as entry co-receptors for HIV. The cytokine network is constitutively activated in most HIV-infected individuals, as demonstrated by recent analysis of intracellular signalling molecules such as the Janus kinase/signal transducer and activator of transcription pathway. Finally, cytokines have already shown their potential use as pharmacological agents able to restore at least some of the compromised immune functions in infected individuals, as exemplified by the potent enhancing effect of IL-2 on the number of circulating CD4+ T lymphocytes.

IL-13 and IFN-γ Secretion by Activated T Cells in HIV-1 Infection Associated with Viral Suppression and a Lack of Disease Progression

The immunopathology of HIV-1 infection includes immune defects in T cell cytokine secretion, resulting in decreased Ag-specific responses. In this report, IL-13 and IFN-γ were analyzed in progressive HIV-1 disease. Both cytokines exert positive effects on Ag presentation and inhibit HIV-1 infection of macrophages. Anti-CD3/anti-CD28-activated PBMC from HIV-1-infected individuals (n = 74) compared with uninfected subjects (n = 30) secreted significantly less IL-13 (median, 0.64 ng/ml vs 2.07 ng/ml; p &lt; 0.001) and IFN-γ (median, 40.96 ng/ml vs 129.5 ng/ml; p &lt; 0.005). Decreased IL-13 and IFN-γ secretion in HIV infection was present in sorted CD4+ and CD8+ T cell subsets, and additional analysis determined concurrent deficiency at the protein and transcriptional level. Longitudinal analysis showed that cytokine secretion levels correlated positively with CD4 count and negatively with plasma HIV-1 viral load. Patients changing to suppressive antiretroviral therapy during the study showed increases in IL-13 and IFN-γ secretion. Overall, results show a decline in IL-13 and IFN-γ secretion in progressive HIV-1 infection and suggest a role for both cytokines as part of T cell adaptive responses associated with a lack of disease progression.

Type 1 and Type 2 Cytokine Regulation of Macrophage Endocytosis: Differential Activation by IL-4/IL-13 as Opposed to IFN-γ or IL-10

Cytokine regulation of endocytic activity in primary human macrophages was studied to define ultrastructural changes and mechanisms of pinocytic regulation associated with cytokines secreted by activated T cells. The effects of IFN-γ (type 1) and IL-4/IL-13 and IL-10 (type 2) cytokines on fluid phase and mannose receptor-mediated endocytosis were assessed by horseradish peroxidase and colloidal gold-BSA uptake and computer-assisted morphometric analysis. IL-4 and IL-13 enhanced fluid phase pinocytosis and mannose receptor-mediated uptake by activation of phosphatidylinositol 3-kinase. Inhibition of actin assembly showed that both cytokines exerted actin-dependent and -independent effects. Ultrastructurally, IL-4 and IL-13 increased tubular vesicle formation underneath the plasma membrane and at pericentriolar sites, concurrent with decreased particle sorting to lysosomes. By contrast, IL-10 or IFN-γ decreased both fluid phase pinocytosis and mannose receptor-mediated uptake. IFN-γ stimulated increased particle sorting to perinuclear lysosomes, while IL-10 decreased this activity. In summary, our data document differential effects on macrophage endocytic functions by type 1 or type 2 cytokines associated with induction and effector pathways in immunity.

Interleukin-4 and interleukin-13: their similarities and discrepancies

Interleukin-4 (IL-4) and the closely related cytokine, interleukin-13 (IL-13) share many biological and immunoregulatory functions on B lymphocytes, monocytes, dendritic cells and fibroblasts. Both IL-4 and IL-13 genes are located in the same vicinity on chromosome 5 and display identical major regulatory sequences in their respective promoters, thus explaining their restricted secretion pattern to activated T cells and mast cells. The IL-4 and IL-13 receptors are multimeric and share at least one common chain called IL-4R alpha. Recent progress made in the description of IL-4 and IL-13 receptor complex have demonstrated the existence of two types of IL-4 receptors: one constituted by the IL-4R alpha and the gamma c chain, and a second constituted by the IL-4 R alpha and the IL-13R alpha 1 and able to transduce both IL-4 and IL-13 signals. Specific IL-13 receptors are results from the association between the IL-4R alpha and the IL-13R alpha 2 or between two IL-13R alpha. Furthermore, similarities in IL-4 and IL-13 signal transduction have been also described, thus explaining the striking overlapping of IL-4- and IL-13-induced biological activities such as regulation of antibody production and inflammation. However, the restricted expression of IL-4 to type 2 helper T lymphocytes as well as the inability of IL-13 to regulate T cell differentiation due to a lack of IL-13 receptors on T lymphocytes represent the major differences between these cytokines. This would indicate that although IL-4 and IL-13 share a large number of properties, precise mechanisms of regulation are also present to guarantee their distinct functions.

Mouse IL-13 Enhances Antibody Production In Vivo and Acts Directly on B Cells In Vitro to Increase Survival and Hence Antibody Production

IL-13, a Th2 cytokine, exhibits similar functions to IL-4 in stimulating proliferation and class switching of human B cells. Although mouse B cells were reported to be unresponsive to IL-13, we now show that IL-13 directly stimulates mouse B cells, causing extended survival and higher Ab levels. Recombinant mouse IL-13 was administered via osmotic pump during immunization of BALB/c mice with chicken RBCs. IL-13 treatment enhanced not only the plasma levels of total IgG1, IgG2a, and IgG2b but also Ag-specific Ig levels. To examine whether IL-13 acted directly on mouse B cells, B220+ B cells were cultured with fixed, anti-CD3-activated Th2 clones. Production of IgM and IgG1 was enhanced moderately by IL-13 and strongly by IL-4. Anti-CD40-stimulated sIgD+ mouse B cells also responded to IL-13 by producing increased levels of IgM, and to a lesser extent IgG1, IgG2a, IgG2b, and IgG3. No evidence was found for IL-13-induced class switching. Mouse B cells were stimulated directly rather than indirectly via contaminating cells, as IL-13 increased the numbers of both total and Ab-secreting B cells in aliquots of 100 sIgD+ B cells (&gt;99.5% pure) stimulated with anti-CD40 Ab. Stimulation of B cells by IL-13 was unaffected by the addition of anti-IL-4 to the cultures. In contrast to IL-4, IL-13 did not increase CD23 expression or B cell proliferation as measured by dilution of an intracellular fluorescence label. Collectively, these data indicate that IL-13 can enhance mouse B cell Ab production by increasing survival of the B cells.

IL-13 Suppresses TNF-Induced Activation of Nuclear Factor-κB, Activation Protein-1, and Apoptosis

IL-13 is known to suppress the production of inflammatory cytokines such as TNF. Whether IL-13 also modulates the biologic effects of TNF is not known. In the present report we examined the effect of IL-13 on TNF-induced activation of nuclear transcription factors NF-κB and activation protein-1 (AP-1) and apoptosis. Pretreatment of cells with IL-13 blocked TNF-induced NF-κB activation, nuclear translocation of p65 subunit, and degradation of IκBα. IL-13 also inhibited NF-κB activation by LPS, okadaic acid, H2O2, and ceramide. TNF-induced NF-κB-dependent gene transcription was also blocked by IL-13. TNF-induced activation of another nuclear transcription factor, AP-1, was suppressed by IL-13. The activation of N-terminal c-Jun kinase and mitogen-activated protein kinase kinase, implicated in the regulation of AP-1 and NF-κB, was also down-regulated by IL-13. TNF-mediated cytotoxicity and activation of caspase-3 were abolished by IL-13. The inhibitory effects of IL-13 on TNF were sensitive to H-7, neomycin, and wortmannin, suggesting that the pathway consisting of protein kinase C, phosphatidylinositol 3-kinase, and phospholipase C must be involved in IL-13 signaling. Thus, overall, these results demonstrate that IL-13 is a potent inhibitor of TNF-mediated activation of NF-κB, AP-1, and apoptosis, which may contribute to its previously described immunosuppressive and anti-inflammatory effects.

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.

Activated lymphocytes from breast cancer patients express the characteristics of type 2 helper cells--a possible role for breast cancer-associated p43

P43, a breast cancer-associated antigen, has been repeatedly described as an immunosuppressive factor. The objective of the present study was to investigate whether immune dysregulation induced by p43 affects the profile of cytokines secreted by mitogen-stimulated lymphocytes in breast cancer patients as compared with stimulated lymphocytes in women with benign tumors. The study consisted of 32 women undergoing surgical excision for a suspicious lesion in their breast. Histology revealed malignant breast disease in 20 patients and benign lesions in 10 patients. Lymphocytes isolated from peripheral blood were activated by Conconavalin A (Con A) with and without the addition of p43 and the concentrations of cytokines (IL-2, TNF-alpha, IFN-gamma, IL-4, IL-10 and IL-6) secreted into the culture medium were determined. Lymphocytes of patients with malignant breast disease stimulated with Con A secreted a significantly higher concentration of IL-10 compared with lymphocytes of patients with benign tumors. No significant differences were found between the two groups regarding the levels of IL-2, TNF-alpha, IFN-gamma and IL-4. Cytokine concentrations were analyzed according to the type 1/type 2 cytokine profile (IL-2, TNF and IFN-gamma and IL-4, IL-6 and IL-10, respectively). This analysis revealed no significant differences in IL-2, TNF or IFN-gamma between benign and malignant tumors. However, in the type 2 cytokines, lymphocytes from cancer patients secreted significantly higher levels of IL-4 (27.3 +/- 7.2 U/ml) and IL-10 (44.1 +/- 22.3 U/ml) than did the lymphocytes from patients with benign disease (21.4 +/- 7.3 and 1.8 +/- 0.3 U/ml, respectively). The addition of p43 to the culture medium significantly enhanced the levels of IL-4 secreted by lymphocytes in both groups of patients (malignant disease, from 27.3 +/- 9.2 to 40.7 +/- 6.3 U/ml; benign disease, from 21.4 +/- 7.3 to 28.4 +/- 2.1 U/ml). P43 antigen significantly enhanced the low levels of IL-10 in the benign lymphocytes (from 1.8 +/- 0.4 to 8.4 +/- 1.5 U/ml) while the high levels of IL-10 secreted by the PBL in patients with malignant tumors were not significantly increased (44.1 +/- 22.3 versus 50.1 +/- 12.6 U/ml). The study showed a difference in the immune response of lymphocytes between malignant and benign tumors. When the current results were analyzed according to the type of response, i.e. in terms of whether at least two cytokines of either type 1 or type 2 were elevated, a significant type 2 response was observed in the PBL of patients with malignant breast cancer (IL-10 and IL-4). These results may explain why antitumor response is impaired in patients with breast cancer.

Immunomodulatory properties of antiviral acyclic nucleotide analogues: cytokine stimulatory and nitric oxide costimulatory effects

Acyclic nucleotide analogues exhibit strong activity against a broad range of viruses, including HIV-1 and -2. We have investigated their effects on in vitro secretion of cytokines and production of nitric oxide (NO) by murine peritoneal macrophages, factors known to play a role in virus replication. Included in the study were the most prominent compounds of the series: 9-(2-phosphonomethoxyethyl)adenine, 9-(2-phosphonomethoxyethyl)-2,6-diaminopurine, the (R)- and (S)-enantiomers of 9-(2-phosphonomethoxypropyl) adenine [(R)- or (S)-PMPA], (R)- and (S)-enantiomers of 9-(2-phosphonomethoxypropyl)-2,6-diaminopurine [(R)- or (S)-PMPDAP], 9-(2-phosphonomethoxyethyl)guanine (PMEG), and (S)-enantiomer of 1-(3-hydroxy-2-phosphonomethoxypropyl)cytosine [(S)-HPMPC]. PMEG, (R)-PMPA, and (S)-PMPA greatly enhanced the secretion of both tumour necrosis factor-alpha (TNF-alpha) and interleukin-10 (IL-10), (R)-PMPDAP stimulated only TNF-alpha, other test compounds were ineffective. None of them influenced the secretion of IL-2 or interferon-gamma (IFN-gamma). Both TNF-alpha and IL-10 have been found to be major factors determining enhancing effects of PMEG, (R)-PMPA, and (S)-PMPA on production of NO generated by exogenous IFN-gamma. The study points to a possible implication of immunomodulatory properties in the antiviral effects of some acyclic nucleotide analogues. In addition, our data support the view that endogenous IL-10 can stimulate certain macrophage functions.

Antiretroviral agent (R)-9-(2-phosphonomethoxypropyl)adenine stimulates cytokine and nitric oxide production

The immunomodulatory properties of (R)-enantiomer of 9-(2-phoshonomethoxypropyl)adenine ((R)-PMPA), one of the most potent acyclic nucleotide analogs effective against human immunodeficiency virus (HIV), were investigated under in vitro conditions using murine peritoneal macrophages. Remaining without influence on interferon-gamma and interleukin-2 expression, (R)-PMPA dramatically stimulated in a concentration- and time-dependent manner the secretion of tumor necrosis factor alpha (TNF-alpha) and interleukin-10. It also substantially augmented the production of nitric oxide (NO) induced by exogenous interferon-gamma. Inhibitory experiments using neutralizing antibodies against TNF-alpha and/or interleukin-10 demonstrated that these two cytokines are major factors responsible for triggering the underlying mechanism(s) leading to enhanced NO production. The novel findings on the immunomodulatory potential of acyclic nucleotide analogs are discussed in the context of their possible implication in antiviral therapeutic efficacy.

Differential Effects of Interleukin-13 on Cytomegalovirus and Human Immunodeficiency Virus Infection in Human Alveolar Macrophages

Alveolar macrophages, which form a principal line of defense against a variety of pulmonary pathogens, may themselves be infected by viruses like human immunodeficiency virus-1 (HIV-1), which impair their defensive functions. Interleukin-13 (IL-13), a multifunctional cytokine, has been considered for therapeutic use based on its potent inhibition of HIV-1 in these cells. We have further examined the effects of IL-13 on alveolar macrophages under conditions that reflect those seen in acquired immune deficiency syndrome, where this cell type is often infected by the opportunistic pathogen human cytomegalovirus (HCMV). Alveolar macrophages exposed to both HCMV and HIV-1 consistently exhibited higher levels of HIV-1 replication than cells exposed to HIV-1 alone. HIV-1 production was strongly suppressed in alveolar macrophages treated with IL-13 regardless of whether or not the cultures were coinfected with HCMV. However, IL-13 treatment markedly enhanced the expression of HCMV in otherwise latently infected macrophages in a dose dependent manner. These unexpected differential effects of IL-13 on host-virus interactions are important considerations in guiding its potential therapeutic applications.

55- and 75-kilodalton tumor necrosis factor receptors mediate distinct actions in regard to human immunodeficiency virus type 1 replication in primary human macrophages

We report in this study that repeated tumor necrosis factor alpha (TNF-alpha) pretreatment, starting before and continued after infection by human immunodeficiency virus type 1 (HIV-1), inhibits replication of the monocytotropic Ada strain in primary tissue culture-differentiated macrophages (TCDM), as assessed by sixfold lower levels of reverse transcriptase (RT) activity than that in untreated cells and absence of syncytium formation in TCDM cultures. In order to determine the pathways involved in inhibition of HIV-1 replication in primary TCDM pretreated with TNF-alpha, we tested TNF-alpha mutants T55 and T75, which recognize either the 55-kDa (TNF-R1) or the 75-kDa (TNF-R2) TNF receptor, respectively. Pretreatment of TCDM with the T75 mutant decreased the RT activity compared with that in untreated infected control cells fivefold and almost totally inhibited syncytium formation. In contrast, when TCDM were pretreated with the T55 mutant alone, syncytia were observed and RT activity was decreased about one-half. These results suggest that the inhibition of HIV-1 replication in TCDM pretreated with TNF-alpha might be mediated mainly through the 75-kDa TNF receptor (TNF-R2) rather than through the 55-kDa receptor (TNF-R1). Inhibition of HIV-1 replication in TCDM was observed with both T75 mutant pretreatment and posttreatment, starting at 1 h or 3 days after infection, whereas posttreatment with the T55 mutant, but not pretreatment, stimulated HIV-1 growth in primary TCDM. Both pre- and posttreatment with TNF-alpha inhibited HIV-1 replication in primary TCDM. The stimulation of HIV-1 replication by TNF-alpha in a chronically infected promonocytic cell line, U1, which contains two copies of integrated provirus, was mediated through the 55-kDa TNF-R1 alone and not through the 75-kDa TNF-R2. These results demonstrate that the 55-kDa TNF-R1 is involved in postintegration stimulation of HIV-1 while the 75-kDa TNF-R2 is involved in the inhibition of an early step of the viral life cycle in primary human TCDM.

Interleukin (IL) 1beta, IL-1 receptor antagonist, IL-10, and IL-13 gene expression in the central nervous system and anterior pituitary during systemic inflammation: pathophysiological implications

The pathophysiology of systemic inflammation and sepsis involves peripheral organs, causing gastrointestinal, renal, and cardiovascular alterations, as well as the central nervous system (CNS), affecting sleep, temperature regulation, behavior, and neuroendocrine function. The molecular basis of the CNS effects of systemic inflammation are not fully elucidated. Here we show that the CNS responds to systemic inflammation with pronounced IL-1beta gene expression and limited IL-1 receptor antagonist (IL-1ra), IL-10, and IL-13 gene expression. This pattern occurs throughout the CNS, including areas such as the subfornical organ, pineal gland, neurohypophysis, and hypothalamus. In contrast, in the anterior pituitary, we found limited IL-1beta gene expression but marked induction of the mRNA encoding for the secreted isoform of IL-1ra, secreted IL-1ra. We conclude that the central manifestations of peripheral inflammation are mediated by endogenous brain IL-1beta synthesized during systemic inflammation in the context of limited central cytokine counter regulation of IL-1. As IL-1beta is a potent stimulus for inducible nitric oxide synthase expression and activity, these findings explain our previous observation that systemic inflammation promotes inducible nitric oxide synthase gene expression in the brain and the spillover of NO metabolites into cerebrospinal fluid. The CNS transcription of the HIV-1 replication factor IL-1beta in the context of limited transcription of the IL-1 replication inhibitors IL-1ra, IL-10, and IL-13 might help explain the negative impact of systemic inflammation on the clinical course of AIDS. In addition, we propose that IL-1ra may be secreted by the anterior pituitary as a systemic anti-inflammatory hormone that is released in response to IL-1beta originated from multiple sources.

Escape of human immunodeficiency virus from immune control

Cytotoxic T lymphocytes (CTL) play a crucial role in the attempt to control infection with human immunodeficiency virus (HIV). Variation in epitopes recognized by CTL is common and frequently offers potential escape routes for mutant virus. Proof of escape, however, requires demonstration of increased frequency of virus particles or provirus that carry the escape sequence. There are now several recorded examples of virus variants that escape from CTL and are then selected. Most dramatic are those in which the CTL response has been dominated by CTL recognizing a single epitope that has suddenly changed, resulting in escape to fixation. This has been seen both early and late in the infection, leaving no doubt that escape occurs. Such escape is likely to be favored when the antiviral CTL response is oligoclonal and focused on a small number of immunodominant epitopes. The heterogeneous CTL response seen in many HIV-infected patients may result from successive waves of virus escape followed by new CTL responses specific for subdominant epitopes. Mutant virus can escape by several different routes, including failure of the mutated peptide to bind to the presenting HLA molecule and altered interactions with T cell receptors (TCR), including antagonism.

CD8+ T-cell-derived soluble factor(s), but not beta-chemokines RANTES, MIP-1 alpha, and MIP-1 beta, suppress HIV-1 replication in monocyte/macrophages

It has been demonstrated that CD8+ T cells produce a soluble factor(s) that suppresses human immuno-deficiency virus (HIV) replication in CD4+ T cells. The role of soluble factors in the suppression of HIV replication in monocyte/macrophages (M/M) has not been fully delineated. To investigate whether a CD8+ T-cell-derived soluble factor(s) can also suppress HIV infection in the M/M system, primary macrophages were infected with the macrophage tropic HIV-1 strain Ba-L. CD8+ T-cell-depleted peripheral blood mononuclear cells were also infected with HIV-1 IIIB or Ba-L. HIV expression from the chronically infected macrophage cell line U1 was also determined in the presence of CD8+ T-cell supernatants or beta-chemokines. We demonstrate that: (i) CD8+ T-cell supernatants did, but beta-chemokines did not, suppress HIV replication in the M/M system; (ii) antibodies to regulated on activation normal T-cell expressed and Secreted (RANTES), macrophage inflammatory protein 1 alpha (MIP-1 alpha) and MIP-1 beta did not, whereas antibodies to interleukin 10, interleukin 13, interferon alpha, or interferon gamma modestly reduced anti-HIV activity of the CD8+ T-cell supernatants; and (iii) the CD8+ T-cell supernatants did, but beta-chemokines did not, suppress HIV-1 IIIB replication in peripheral blood mononuclear cells as well as HIV expression in U1 cells. These results suggest that HIV-suppressor activity of CD8+ T cells is a multifactorial phenomenon, and that RANTES, MIP-1 alpha, and MIP-1 beta do not account for the entire scope of CD8+ T-cell-derived HIV-suppressor factors.

Immunohistochemical identification of type II alternatively activated dendritic macrophages (RM 3/1+3, MS-1+/-, 25F9-) in psoriatic dermis

Immunological mechanisms play an important role in the pathogenesis of psoriasis. Lesional psoriatic skin-derived T-cell clones have been shown to stimulate keratinocyte proliferation and to predominantly express a T-helper type 1 cytokine pattern. However, T-helper type 2-like cytokines have also been identified in some psoriatic T-cell clones. In parallel to the T-helper type 1/type 2 dichotomy, a distinction between interferon-gamma-induced (classically activated) macrophages and interleukin-4/glucocorticoid-induced (alternatively activated) macrophages has been put forward as a conceptual framework for a better understanding of immunopathological processes. In the present study, the phenotype of mononuclear phagocytes in psoriatic skin lesions (n = 21), allergic contact dermatitis (n = 4) and normal skin (n = 2) was investigated using a panel of monoclonal antibodies (mAb) against monocytes/macrophages and dendritic cells (mAb MS-1, RM 3/1, and 25F9 against subsets of in vitro alternatively activated macrophages, and mAb against myeloid antigens CD1a, CD11b, CD11c, CD34, CD36, and CD68). With regard to mononuclear phagocytes, psoriatic skin was found to be compartmentalized into epidermis, subepidermal space, and upper and lower dermis. RM 3/1++ +, MS-1+/-, 25F9- dendritic macrophages previously classified as type II alternatively activated macrophages were the dominant dermal macrophage population in psoriatic skin, while intraepidermal and epithelium-lining macrophages expressed a different, presumably classically activated, macrophage phenotype (RM 3/1-, MS-1-, 25F9-, CD68+2, CD11b+2). In allergic contact dermatitis, a classical T-helper type 1 disease, RM 3/1++ + macrophages were less prominent. Since MS-1 high molecular weight protein is much more sensitive to interferon-gamma-induced suppression than RM 3/1 antigen, a predominance of T-helper type 1 cytokines in psoriasis could explain why dermal dendritic macrophages do not express the fully induced MS-1++ +, RM 3/1++ +, 25F9+/- phenotype of type I alternatively activated macrophages.

Cytokines at the research-clinical interface: potential applications

Developments in the characterization of growth factors and the recognition of their potential for clinical use has advanced through a number of stages. The development of clonogenic haemopoietic colony assays in the 1960s led to the discovery of colony-stimulating activity in the conditioned medium produced by certain cell lines. This activity was then purified and the colony-stimulating factors were identified. With rapid progress in molecular biology techniques in the 1980s, many further growth factors were cloned and produced on an industrial scale. Although erythropoietin, interferons, G-CSF, GM-CSF and IL-2 were all introduced into clinical practice as single agents, cytokines have more recently been investigated for use either in combination, or sequentially. Clinical trials are currently in progress to examine the optimum combinations and timing of administration. Current clinical applications include optimization of methods for mobilization of peripheral blood progenitor cells and amelioration of cytopenias following chemotherapy and bone-marrow transplantation. In the future, cytokines will be employed to expand stem and progenitor cells ex vivo, to improve gene transduction strategies, possibly to protect the gastrointestinal epithelium and as immunomodulators, both in vivo and in vitro. This review will focus on recently characterized growth factors including c-kit ligand/stem cell factor, flt3 ligand, c-mpl ligand/thrombopoietin and interleukins-11, 4, 7, 10, 12 and 13.

Lipopolysaccharide (LPS) down-regulates CD4 expression in primary human macrophages through induction of endogenous tumour necrosis factor (TNF) and IL-1 beta

The regulation of CD4 expression on macrophages and its role in immune cell interactions remain obscure. In contrast with primary lymphocytes, primary macrophages express only low amounts of surface CD4, which is regulated differentially for example by adherence in vitro. We report that addition of LPS for 1-5 days to human blood monocyte tissue culture-derived macrophages (TCDM) down-regulates both surface CD4 expression and total cellular CD4 antigen content as measured by flow cytometry and Western blot analysis. TNF-alpha and IL-1 beta, proinflammatory cytokines which are both induced by LPS, also down-regulate surface and total CD4 expression in TCDM. This down-regulation of CD4 expression by LPS, TNF-alpha, and IL-1 beta occurs at the level of transcription. The decreased macrophage CD4 expression induced by LPS was blocked by MoAbs directed against human TNF-alpha and IL-1 beta, demonstrating that LPS acts on CD4 expression through induction of endogenous TNF-alpha and IL-1 beta. Conversely, neither LPS nor TNF-alpha and IL-1 beta were able to modulate surface CD4 expression on quiescent or phytohaemagglutinin (PHA)-activated lymphocytes. Of other cytokines and growth factors tested, Th2 cytokines (IL-4, IL-10, IL-13), chemokines (MCP-1, MIP-1 alpha, RANTES), and macrophage colony-stimulating factor did not alter CD4 expression in primary macrophages; granulocyte-monocyte colony-stimulating factor and the prototypal Th1 cytokine interferon-gamma (IFN-gamma) modulated surface CD4 expression only after prolonged treatment (5 days). Our results show that LPS, TNF-alpha and IL-1 beta selectively down-regulate CD4 expression in primary human macrophages, and that decreased CD4 expression induced by LPS results from endogenous secretion of TNF-alpha and IL-1 beta by the macrophages.