Altered production of tumour necrosis factors alpha and beta and interferon gamma by HIV-infected individuals

Increased expression of IL-32 correlates with IFN-γ, Th1 and Tc1 in virologically suppressed HIV-1-infected patients

Following recent attention focused on IL-32 as an important component involved in the inflammatory cytokine network, we speculated that IL-32's action on IFN-γ and IFN-γ secreting T cell subsets may help sustain the immune activation and dysregulation found in patients with HIV-1 achieving viral suppression. To explore this hypothesis, transcript levels of IL-32 and IFN-γ were evaluated in PBMC from 139 virologically suppressed HIV-1-infected patients and from 63 healthy individuals by Real Time RT-PCR assays. IL-32 and IFN-γ mRNA levels were also analyzed in CD4+ T cells, CD14+ monocytes and lamina propria lymphocytes (LPL) of the gut district in a subgroup of HIV-1-infected subjects. IFN-γ secreting CD4+ (Th1) and CD8+ (Tc1) T cell subset frequencies were evaluated in LPL by multiparametric flow cytometry. Gene expression results revealed that IL-32 and IFN-γ levels in PBMC from HIV-1-positive patients were significantly elevated compared to those from healthy donors, correlated with each other and increased with patient age. Both IL-32 and IFN-γ genes were also more strongly expressed in CD4+ T cells than in CD14+ monocytes. By contrast, IL-32 levels in LPL were comparable to those measured in PBMC, while IFN-γ levels were higher in PBMC than those in LPL. Negative correlations were found between IL-32 levels and the frequencies of Th1 and Tc1 subsets in gut mucosa. Collectively, our results provide the first evidence that IL-32 levels remain elevated in treated HIV-1-infected patients and correlate with IFN-γ, Th1 and Tc1 subsets.

Type I interferon and HIV: Subtle balance between antiviral activity, immunopathogenesis and the microbiome

•

Induction and action of IFN during acute and chronic HIV-1 infection.

•

Host and viral factors influencing IFN response in HIV-1 infected patients.

•

Type I IFN and IFNα subtypes signatures and their antiviral activity during HIV-1 infection.

•

The microbiome and intestinal IFN responses relationship in HIV-1 infection and disease.

Type I interferon (IFN) response initially limits HIV-1 spread and may delay disease progression by stimulating several immune system components. Nonetheless, persistent exposure to type I IFN in the chronic phase of HIV-1 infection is associated with desensitization and/or detrimental immune activation, thereby hindering immune recovery and fostering viral persistence. This review provides a basis for understanding the complexity and function of IFN pleiotropic activity in HIV-1 infection. In particular, the dichotomous role of the IFN response in HIV-1 immunopathogenesis will be discussed, highlighting recent advances in the dynamic modulation of IFN production in acute versus chronic infection, expression signatures of IFN subtypes, and viral and host factors affecting the magnitude of IFN response during HIV-1 infection. Lastly, the review gives a forward-looking perspective on the interplay between microbiome compositions and IFN response.

Addition of maraviroc to antiretroviral therapy decreased interferon-γ mRNA in the CD4+ T cells of patients with suboptimal CD4+ T-cell recovery

The CCR5 antagonist, maraviroc (MVC), is associated with an enhanced CD4+ T-cell response independent of virological suppression; however, its mechanism of action has not been elucidated. In this study, we confirmed the effect of MVC on CD4+ T-cell count recovery in immunological non-responders, and compared the conventional combination antiretroviral therapy (cART) with MVC-intensified cART. We also investigated the effect of MVC on interferon-γ (IFN-γ) production in CD4+ T cells in vitro and in vivo, and evaluated the relationship between the mRNA level of IFN-γ and the degree of CD4+ T-cell count recovery. In vitro analysis indicated that MVC significantly decreased mRNA levels of IFN-γ in HIV-Tat stimulated CD4+ T cells from healthy donor peripheral blood mononuclear cells. Of the 18 HIV-infected patients treated with MVC-intensified cART, 12 had a significantly increased CD4+ T-cell count after 24 weeks of additional treatment with MVC. In patients exhibiting a response in CD4+ T-cell counts, mRNA levels of IFN-γ in CD4+ T cells were lower than those in patients showing a non-response at baseline and at week 24, while mRNA levels of IFN-γ decreased in both groups at 24 weeks. In conclusion, MVC decreased the mRNA level of IFN-γ in CD4+ T cells in vitro and in vivo, especially in patients whose CD4+ T-cell count increased significantly. We also found that the lower baseline IFN-γ mRNA level and the larger decreased rate of IFN-γ mRNA in CD4+ T cells were associated with a good response to MVC regarding CD4+ T-cell recovery.

Acquisition of host-derived CD40L by HIV-1 in vivo and its functional consequences in the B-cell compartment

Aberrant activation of the B-cell compartment and hypergammaglobulinemia were among the first recognized characteristics of HIV-1-infected patients in the early 1980s. It has been demonstrated previously that HIV-1 particles acquire the costimulatory molecule CD40L when budding from activated CD4(+) T cells. In this paper, we confirmed first that CD40L-bearing virions are detected in the plasma from untreated HIV-1-infected individuals. To define the biological functions of virus-associated CD40L and fully characterize its influence on the activation state of B cells, we conducted a large-scale gene expression analysis using microarray technology on B cells isolated from human tonsillar tissue. Comparative analyses of gene expression profiles revealed that CD40L-bearing virions induce a highly similar response to the one observed in samples treated with a CD40 agonist, indicating that virions bearing CD40L can efficiently activate B cells. Among modulated genes, many cytokines/chemokines (CCL17, CCL22), surface molecules (CD23, CD80, ICAM-1), members of the TNF superfamily (FAS, A20, TNIP1, CD40, lymphotoxin alpha, lymphotoxin beta), transcription factors and associated proteins (NFKB1, NFKBIA, NFKBIE), second messengers involved in CD40 signaling (TRAF1, TRAF3, MAP2K1, phosphatidylinositol 3-kinase), and the activation-induced cytidine deaminase (AID) were identified. Moreover, we show that soluble factors induced upon the exposure of B cells to CD40L-bearing virions can exert chemoattractant properties toward CD4(+) T cells. We thus propose that a positive feedback loop involving CD40L-bearing HIV-1 particles issued from CD4(+) T cells productively infected with HIV-1 play a role in the virus-induced dysfunction of humoral immunity by chronically activating B cells through sustained CD40 signaling.

HIV+ elite controllers have low HIV-specific T-cell activation yet maintain strong, polyfunctional T-cell responses

OBJECTIVE

HIV elite controllers are a unique group of rare individuals who maintain undetectable viral loads in the absence of antiretroviral therapy. We studied immune responses in these individuals to inform vaccine development, with the goal of identifying the immune correlates of protection from HIV.

METHODS

We compared markers of cellular activation, HIV-specific immune responses and regulatory T (Treg) cell frequencies in four groups of individuals: HIV-negative healthy controls, elite controllers (HIV RNA level <75 copies/ml), individuals on HAART and individuals with HIV RNA level more than 10,000 copies/ml (noncontrollers).

RESULTS

Elite controllers possessed significantly lower levels of activated HIV-specific CD8 T cells and of recently divided HIV-specific CD4 T cells than noncontrollers, whereas these differences were not seen in the respective cytomegalovirus-specific T-cell populations. Elite controllers also mounted a stronger and broader cytokine and chemokine response following HIV-specific stimulation than individuals on HAART and noncontrollers. Finally, we found that HAART-suppressed individuals had elevated Treg cell frequencies, whereas elite controllers and noncontrollers maintained normal percentages of Treg cells.

CONCLUSION

Elite controllers maintain high levels of HIV-specific immune responses with low levels of HIV-specific T-cell activation and do not have elevated Treg cell levels. Based on these data an ideal HIV vaccine would induce strong HIV-specific immune responses whereas minimizing HIV-specific T-cell activation.

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.

HIV infection and aging: enhanced Interferon- and Tumor Necrosis Factor-alpha production by the CD8+ CD28- T subset

BACKGROUND

T cells from HIV+ and aged individuals show parallels in terms of suppressed proliferative activity and interleukin-2 (I1-2) production and an increased number of CD8+ CD28- T cells. In order to compare cytokine production from T cells from these two states, CD4+ and CD8+ T cells from HIV+ aged, and normal young donors (controls) were monitored for cytokine production by flow cytometry, quantitative PCR and ELISA upon activation by PMA and anti-CD3. In addition, the CD8+ T cell subsets CD28+ and CD28- from the HIV+ and the aged groups were evaluated for cytokine production by flow cytometry, and compared with those from young controls.

RESULTS

Flow cytometric analysis indicated that CD8+ T cells from both HIV+ and aged donors showed an increase of approximately 2-3 fold over controls in percentage of cells producing inflammatory cytokines IFN-gamma and TNF-alpha. Similar analysis also revealed that the production of interleukins-4,6 and 10, production was very low (1-2% of cells) and unchanged in these cells. Quantitative PCR also showed a substantial increase (4-5 fold) in IFN-gamma and TNF-alpha mRNA from HIV+ and aged CD8+ T cells, as did ELISA for secreted IFN-gamma and TNF-alpha (2.3-4 fold). Flow cytometric analysis showed that the CD8+ CD28- T cell subset accounts for approximately 80-86% of the IFN-gamma and TNF-alpha production from the CD8+ subset in the aged and HIV+ states. The CD4+ T cell, while not significantly changed in the HIV+ or aged states in terms of IFN-gamma production, showed a small but significant increase in TNF-alpha production in both states.

CONCLUSIONS

Our data appear compatible with physiologic conditions existing in HIV+ and aged individuals, i.e. elevated serum levels and elevated CD8+ T cell production of IFN-gamma and TNF-alpha. Thus, the capacity for increased production of cytokines IFN-gamma and TNF-alpha in the aged individual by the dominant CD8+ CD28- subset may have a profound influence on the clinical state by aggravating inflammatory pathologies such as rheumatoid arthritis, and possibly Alzheimer's disease and Crohn's disease. In AIDS, these cytokines may contribute to wasting and cachexia. We theorize that the predominant phenotypic change to the cytotoxic CD8+ CD28- T cell subsets in both the HIV+ and the aged states may reflect a natural "endpoint" in CD8+ T cell differentiation induced after a lifetime of immune activity (toward viruses, etc) in the aged, and after a massive accelerated response to HIV in the HIV-positive individual.

Peripheral blood cell-specific cytokines in persons with untreated HIV infection in Malawi, Africa

Human immunodeficiency virus (HIV) infection is the primary cause of morbidity and mortality in Malawi, Africa, because of its many effects on the immune system. Immune cells communicate through cytokines; therefore, we examined the relationships between HIV serostatus and cell-specific cytokine production for 40 asymptomatic, employed adults and 312 acutely ill, hospitalized patients in Malawi. We also measured the plasma HIV-1 RNA levels of 13 asymptomatic persons and 83 patients found to be HIV(+). We incubated peripheral whole blood with brefeldin-A +/- phorbol 12-myristate 13-acetate and ionomycin and then permeabilized, fixed, fluorescently stained, and examined the mononuclear cells with four-color, six-parameter flow cytometry. The percentage of lymphocytes expressing CD4 did not differ significantly between the HIV(+) and HIV(-) healthy adults (medians, 35.2 vs. 40.8%, respectively), but a wide array of cytokine parameters were lower in the HIV(+) than in the HIV(-) asymptomatic persons, for example, median percentages of T cells producing induced interleukin 2 (IL-2) (8.7 vs. 16.5%, respectively) and spontaneously producing IL-6 (0.7 vs. 11.0%, respectively). Also, four T cell parameters reflecting type 2-to-type 1 cytokine balances (T2/T1) were higher in the HIV(+), versus HIV(-), asymptomatic persons. Unlike the healthy adults, for patients with mycobacteremia/fungemia or malaria, the HIV(+) patients had higher median percentages of T cells and CD8(+) T cells producing induced interferon gamma than did the HIV(-) PATIENTS: For both asymptomatic and acutely ill persons, HIV-1 plasma levels were positively correlated with T2/T1 parameters. Cell-specific cytokine effects of HIV infection may precede measurable effects on CD4 expression. Cytokine therapies, even beyond periodic administration of IL-2, may improve the responses of HIV-infected persons to both HIV and coinfections.

HIV associated thrombotic microangiopathy

Thrombotic microangiopathy (TMA) is a known complication of HIV infection. Endothelial cell injury appears to be the primary event causing platelet activation and deposition in the microvasculature. Direct cytopathic roles of HIV as well as other factors such as malignancy, drugs, and infectious agents have been implicated in the pathogenesis of HIV-TMA. Although the the majority of patients present in a more advanced stage of HIV disease, TMA can be the initial presenting symptom of HIV infection. Clinical features are those of idiopathic TMA, and the diagnosis should be suspected in any patient with new onset thrombocytopenia and microangiopathic haemolytic anaemia. Therapy with plasma exchange or infusion appears to be efficacious. A rapid diagnosis and institution of plasmapheresis is crucial for a favourable outcome. The long term prognosis of HIV-TMA is unfavourable and may depend on the stage of HIV infection. The recent data after the use of highly active retroviral treatment, however, are unavailable and current prognosis is therefore uncertain.

Supernatants of HIV-infected immune cells affect the barrier function of human HT-29/B6 intestinal epithelial cells

OBJECTIVES

Characterization of the diarrhoea-inducing effect of altered cytokine production in HIV infection.

METHODS

Monocyte-derived macrophages (MDM) were infected with macrophagetropic (SF162) and lymphocytotropic (IIIB) HIV-1 strains and cocultured with autologous peripheral blood mononuclear cells (PBMC). After 24 h the supernatants were collected and tested for their immunoreactive levels of cytokines by enzyme-linked immunosorbent assay. The effects of the supernatants and the respective recombinant human cytokines on barrier function of HT-29/B6 cells were determined.

RESULTS

Infection of MDM with HIV-1 SF162 or IIIB led to increased production of tumour necrosis factor-alpha (TNFalpha), interleukin-1-beta, interferon-alpha and interferon-gamma after cell-cell contact with PBMC. Supernatants of infected cells decreased transepithelial resistance (R(t)), with higher effects on R(t) in HIV IIIB infection, which was due to higher cytokine concentrations. The effect was not due to cytotoxicity (negative LDH assay) or epithelial monolayer disruption [zonula occludens protein-1 (ZO-1) immunofluorescence staining]. The effect of HIV-1 IIIB coculture supernatants could be mimicked by the respective recombinant human cytokines. TNFalpha is an effector cytokine, because inhibition of TNFalpha by its soluble receptor decreased the effect of the supernatants on transepithelial resistance. Conductance scanning indicated the cytokine-induced barrier defect to be due to both, induction of epithelial apoptoses and tight junction alterations.

CONCLUSIONS

Cell-cell interaction of HIV-infected macrophages with PBMC leads to a release of cytokines sufficient to alter intestinal epithelial barrier function. The main effect was mediated by TNFalpha inducing a leak-flux which may contribute to the diarrhoea by HIV per se (HIV-enteropathy).

Angiogenic effects of extracellular human immunodeficiency virus type 1 Tat protein and its role in the pathogenesis of AIDS-associated Kaposi's sarcoma

The Tat protein of human immunodeficiency virus (HIV) type 1 is a transactivator of viral gene expression that is required for virus replication and spread. Moreover, Tat is released by acutely HIV-infected cells via a leaderless secretory pathway and in a biologically active form that exerts effects on both HIV-infected and uninfected cells from different organs and systems. This review focuses on the activities of extracellular Tat protein on endothelial cells, on angiogenesis, and on the pathogenesis of AIDS-associated angioproliferative diseases such as Kaposi's sarcoma. In particular, we discuss results from different groups indicating that Tat mimics the proangiogenic activities of extracellular matrix molecules and that it enhances the effects of angiogenic factors.

Serum pepsinogen and gastrin levels in HIV-positive patients: relationship with CD4+ cell count and Helicobacter pylori infection

BACKGROUND

The relationship between serum parameters of gastric function and Helicobacter pylori infection in human immunodeficiency virus (HIV)-positive patients is almost unknown.

AIMS

To investigate in HIV-infected patients: (i) the relationship between serum gastrin and serum pepsinogens over the progressive phases of HIV-related disease; (ii) the impact of H. pylori infection on gastrin and pepsinogen serum levels and its relation to antral histology; (iii) the prevalence of parietal cell autoantibodies.

METHODS

Fifty-nine HIV-positive patients were studied by upper endoscopy plus gastric antral biopsy. Serum samples were tested for gastrin, pepsinogen A, pepsinogen C and parietal cell autoantibodies.

RESULTS

In patients without overt acquired immunodeficiency syndrome (AIDS), or with a CD4+ count of > 100 x 10(6) cells/L, mean serum levels of gastrin and pepsinogen C were higher than in subjects with AIDS or with a CD4+ count of < 100 x 10(6) cells/L (P < 0.01). Only one patient was found to be positive for parietal cell autoantibodies. H. pylori infection was associated with increased values of gastrin and pepsinogen C only in HIV-positive patients without AIDS or with a CD4+ count of > 100 x 10(6) cells/L. Atrophy was more frequent in patients with overt AIDS than in those without overt AIDS (57% vs. 33%, P=N.S.), and/or in patients with a CD4+ count of < 100 x 10(6) cells/L than in those with a CD4+ count of > 100 x 10(6) cells/L (62% vs. 26%, P < 0.05).

CONCLUSIONS

HIV-positive patients without overt AIDS have increased serum levels of gastrin and pepsinogen C compared with HIV-positive patients with overt AIDS.

Reactivation and role of HHV-8 in Kaposi's sarcoma initiation

Kaposi's sarcoma (KS) is an angioproliferative disease occurring in several clinical-epidemio-logic forms but all associated with infection by the human herpesvirus-8 (HHV-8). At least in early stages, KS is a reactive disease associated with a state of immune dysregulation characterized by CD8+ T-cell activation and production of Th1-type inflammatory cytokines (IC) that precedes lesion development. In fact, evidence indicates that IC can trigger lesion formation by inducing the activation of endothelial cells that leads to adhesion and tissue extravasation of lymphomonocytes, spindle cell formation, and angiogenesis, and HHV-8 reactivation that, in turn, leads to virus spread to all circulating cell types and virus dissemination into tissues. Due to virus escape mechanisms and deficient immune responses toward HHV-8, virus reactivation and spread are not controlled by the immune system but induce immune responses that may paradoxically exacerbate the reactive process. The virus is recruited into "activated" tissue sites where it finds an optimal environment for growth. In fact, viral load is very low in early lesions, whereas almost all spindle cells are infected in late-stage lesions. Although early KS is a reactive process of polyclonal nature that can regress, in time and in the presence of immunodeficiency, it can progress to a true sarcoma. This is likely due to the long-lasting expression of HHV-8 latency genes in spindle cells associated with the deregulated expression of oncogenes and oncosuppressor genes and, for AIDS-KS, with the effects of the HIV-1 Tat protein.

The effect of X4 and R5 HIV-1 on C, C-C, and C-X-C chemokines during the early stages of infection in human PBMCs

To better define a mechanism underlying the increase in expression of certain proinflammatory chemokines during HIV-1 infection, we analyzed the effect of X4 HIV-1 infection on C, C-C, and C-X-C chemokine mRNA levels. We demonstrate that X4 HIV-1 infection augments the expression of RANTES, IP-10, MCP-1, and Ltn in peripheral blood mononuclear cells (PBMCs). R5 HIV-1 also induces an increase in both IP-10 and MCP-1 production. Binding of UV-inactivated HIV-1 elevates MCP-1, RANTES, MIP-1alpha, MIP-1beta, and IL-8 expression, but fails to alter the production of IP-10, suggesting that the induction of IP-10 is dependent on downstream events following viral internalization. Indeed, recombinant gp120 alone was able to stimulate an eightfold increase in MCP-1 expression, but was unable to induce any detectable increase in IP-10 protein. HIV-induced modulation of chemokine expression suggests a mechanism by which HIV-infected monocytes and T cells might recruit target cells to sites of active viral replication, thus potentially aiding in the spread of the virus.

Mechanisms of epithelial barrier impairment in HIV infection

Diarrhea and malabsorption due to intestinal dysfunction are common symptoms in HIV infection. The pathophysiologic mechanisms of these alterations are often not known, and the role of HIV per se is still controversially discussed. We measured the epithelial transport and barrier function by means of a miniaturized Ussing chamber system in the duodenum of HIV-infected patients in different disease stages, determined by the CD4 cell count in the serum as well as symptoms in patients with and without diarrhea. We could show that diarrhea induced by HIV per se is caused by a leak flux mechanism due to impaired epithelial barrier function. Antisecretory therapy does not seem to be useful in these patients, because we did not find increased active ion secretion. Along the course of the HIV infection, the epithelial transport and barrier function varies with HIV disease stage (expressed by CD4 cell status). In addition, an in vitro model was studied to characterize the effect of HIV-infected human immune cells on the epithelial barrier function using the human colonic epithelial cell line HT-29/B6. HIV infection of human immune cells induced an increase in cytokine release--for example, TNF-alpha, IL-1 beta, IFN-alpha, and IFN-gamma--downregulating the epithelial barrier function of the human colonic epithelial cell line HT-29/B6. Taken together we postulate a specific stage-dependent cytokine pattern released from HIV-infected immune cells in the mucosa, which, corresponding to the HIV disease stage, is responsible for the variation in epithelial function.

The envelope glycoprotein of simian immunodeficiency virus contains an enterotoxin domain

By the use of a mouse model, the enteropathic effects of the simian immunodeficiency virus (SIV) surface unit (SU) envelope glycoprotein were explored. Purified SU (0.01-0.45 nmol) was administered intraperitoneally to 6- to 8-day-old mouse pups and induced a dose-dependent diarrheal response. Surgical introduction of SU into adult mouse intestinal loops revealed fluid accumulation without histological alterations and SU-treated unstripped intestinal mucosa induced chloride (Cl(-)) secretory currents in Ussing chambers. Similarly to rotavirus NSP4, the first described viral enterotoxin, SU induced a transient increase in intracellular calcium levels and increased inositol 1,4,5-triphosphate (IP(3)) levels in HT-29 cells. These data indicate the calcium response is mediated by IP(3). The presence of diarrhea and fluid accumulation within intestinal loops in the absence of histological alterations and induction of Cl(-) secretory currents demonstrate that SIV contains an enterotoxic domain localized within SU and is the second viral enterotoxin described.

Dysregulation of B7.2 (CD86) expression on monocytes of HIV-infected individuals is associated with altered production of IL-2

T helper (Th) responses are mediated in part by immunoregulatory cytokines and the signals delivered by the costimulatory CD28-B7 pathway. In this study, we have investigated the relationship between the regulation of B7 isoform expression on antigen-presenting cells from HIV+ individuals and the production of Th cytokines. The level of expression of both B7.1 and B7.2 isoforms as measured by mean channel fluorescence was significantly decreased on freshly isolated monocytes from HIV+ individuals compared with HIV- controls. However, the levels of expression of B7.1 and B7.2 on both B cells and monocytes increased significantly following culture in HIV+ individuals compared with HIV- controls. B7 expression is subject to regulation by immunoregulatory cytokines. Therefore, we analysed the regulation of B7 expression by cytokines, namely IL-10 and tumour necrosis factor-alpha (TNF-alpha), the production of which is enhanced in HIV infection and have similar inhibitory effects on B7 expression. Two groups of HIV+ individuals were distinguished on the basis of the inhibitory effect of IL-10 and TNF-alpha on monocyte B7.2 expression. IL-10 inhibited B7.2 expression on monocytes from some HIV+ individuals (termed responders) like the HIV- controls. However, in a subset of HIV+ individuals (non-responders) this inhibitory effect was lost. Loss of inhibition of B7.2 expression by IL-10 was associated with significantly reduced IL-2 production by phytohaemagglutinin (PHA)- stimulated peripheral blood mononuclear cells (PBMC). These observations showing an association of B7 dysregulation on monocytes and B cells with altered production of IL-2 may have implications in HIV immunopathogenesis.

IFN-γ Induces Endothelial Cells to Proliferate and to Invade the Extracellular Matrix in Response to the HIV-1 Tat Protein: Implications for AIDS-Kaposi’s Sarcoma Pathogenesis

Previous studies indicated that the Tat protein of HIV functions as a progression factor in Kaposi’s sarcoma (KS), an angioproliferative disease common and aggressive in HIV-1-infected individuals (AIDS-KS). In particular, Tat that is released by infected cells stimulates the growth and invasion of spindle cells of endothelial origin derived from KS lesions (KS cells). Other work suggested that inflammatory cytokines may act as initiating factors in KS since they induce normal endothelial cells to acquire the same phenotype and functional features of KS cells, including the responsiveness to Tat. In this study, we show that among the inflammatory cytokines increased in AIDS-KS lesions, IFN-γ alone is sufficient to induce endothelial cells to proliferate and to invade the extracellular matrix in response to Tat. This is because IFN-γ up-regulates the expression and activity of the receptors for Tat identified as the integrins α5β1 and αvβ3. These results suggest that, by triggering Tat effects, IFN-γ plays a major role in AIDS-KS pathogenesis.

Tumor necrosis factor-alpha (TNFalpha) regulates the epithelial barrier in the human intestinal cell line HT-29/B6

Cytokines are supposed to be mediators in diarrhoeal diseases. The aim of this study is to characterize the effect of tumor necrosis factor-alpha (TNFalpha) on epithelial barrier function in the colonic epithelial cell line HT-29/B6. Active ion transport and barrier function were measured as short-circuit current and transepithelial electrical resistance (Rt), respectively. In parallel, freeze-fracture electron microscopy (EM) of tight junctions (TJ) and immunofluorescence microscopy of the zonula occludens protein-1 (ZO-1) were performed. Serosal addition of TNF(alpha) (100 ng/ml) decreased Rt by 81%. This effect was dose-dependent and could be mimicked by antibodies against the p55 form of the TNF receptor. Cytotoxic effects were excluded by a negative lactate dehydrogenase (LDH) assay. Immunofluorescence localization with anti-ZO-1 antibodies revealed no evidence for disruption of the monolayer after TNFalpha treatment. In freeze-fracture EM, TJ complexity was decreased by TNFalpha, as indicated by a decrease in the number of strands from 4.7 to 3.4. The tyrosine kinase blocker genistein and the protein kinase A inhibitor H-8 reduced the effect of TNFalpha. A combination of TNFalpha with interferon-gamma acted synergistically on the epithelial barrier. In conclusion, TNFalpha impairs epithelial barrier function by altering structure and function of the tight junction, which could be of pathogenic relevance in intestinal inflammation.

Infection with human immunodeficiency virus type 1 upregulates DNA methyltransferase, resulting in de novo methylation of the gamma interferon (IFN-gamma) promoter and subsequent downregulation of IFN-gamma production

The immune response to pathogens is regulated by a delicate balance of cytokines. The dysregulation of cytokine gene expression, including interleukin-12, tumor necrosis factor alpha, and gamma interferon (IFN-gamma), following human retrovirus infection is well documented. One process by which such gene expression may be modulated is altered DNA methylation. In subsets of T-helper cells, the expression of IFN-gamma, a cytokine important to the immune response to viral infection, is regulated in part by DNA methylation such that mRNA expression inversely correlates with the methylation status of the promoter. Of the many possible genes whose methylation status could be affected by viral infection, we examined the IFN-gamma gene as a candidate. We show here that acute infection of cells with human immunodeficiency virus type 1 (HIV-1) results in (i) increased DNA methyltransferase expression and activity, (ii) an overall increase in methylation of DNA in infected cells, and (iii) the de novo methylation of a CpG dinucleotide in the IFN-gamma gene promoter, resulting in the subsequent downregulation of expression of this cytokine. The introduction of an antisense methyltransferase construct into lymphoid cells resulted in markedly decreased methyltransferase expression, hypomethylation throughout the IFN-gamma gene, and increased IFN-gamma production, demonstrating a direct link between methyltransferase and IFN-gamma gene expression. The ability of increased DNA methyltransferase activity to downregulate the expression of genes like the IFN-gamma gene may be one of the mechanisms for dysfunction of T cells in HIV-1-infected individuals.

Measurement of induced cytokines in AIDS clinical trials using whole blood: a preliminary report. ACTG Inducible Cytokines Focus Group. AIDS Clinical Trials Group

Measures of immune function have become increasingly important as endpoints in AIDS clinical trials, with respect to both modulation and reconstitution of immunity by experimental therapies. Measurement of immune function in this setting requires the development of robust analytic approaches suitable for the clinical laboratory. Experiments were performed to evaluate the suitability of using cultured heparinized ("whole") blood for induction of tumor necrosis factor alpha (TNF-alpha) and gamma interferon (IFN-gamma), two cytokines critical in AIDS pathogenesis. TNF-alpha expression ranged from 229 to 769 pg/ml in lipopolysaccharide (LPS)-stimulated cultures and was not detected in unstimulated cultures. IFN-gamma expression ranged from 0 to 112,000 pg/ml in phytohemagglutinin A (PHA)-stimulated cultures and from 0 to 789 pg/ml in antigen-stimulated cultures. The mean coefficient of variation observed in three weekly determinations was 0.47 for TNF-alpha and ranged from 0.12 to 1.73 for IFN-gamma. These values indicate that sample sizes of 8, 24, and 29 subjects would be sufficient to detect twofold changes in LPS-induced TNF-alpha and in PHA- and antigen-induced IFN-gamma respectively, if two baseline and two treatment determinations were obtained, and if the interpatient variability of changes in true levels from baseline to follow-up is negligible compared to the variability in the three weekly measurements. Measurement of LPS-induced TNF-alpha and mitogen- or antigen-induced IFN-gamma can be performed simply and reproducibly in human immunodeficiency virus-infected persons by the whole-blood culture method. Further studies are warranted to determine the effect of overnight shipping on assay reproducibility and to determine the extent to which responses can be reliably detected in subjects with low CD4 cell numbers.

Vascular endothelial growth factor and basic fibroblast growth factor present in Kaposi's sarcoma (KS) are induced by inflammatory cytokines and synergize to promote vascular permeability and KS lesion development

All forms of Kaposi's sarcoma (KS) are characterized by spindle cell proliferation, angiogenesis, inflammatory cell infiltration, and edema. We have previously reported that spindle cells of primary KS lesions and KS-derived spindle cell cultures express high levels of basic fibroblast growth factor (bFGF), which is promoted by the inflammatory cytokines identified in these lesions. These cytokines, namely, tumor necrosis factor, interleukin-1, and interferon-gamma, induce production and release of bFGF, which stimulates angiogenesis and spindle cell growth in an autocrine fashion. Here we show that both AIDS-KS and classical KS lesions co-express vascular endothelial growth factor (VEGF) and bFGF. VEGF production by KS cells is promoted synergistically by inflammatory cytokines present in conditioned media from activated T cells and in KS lesions. KS cells show synthesis of VEGF isoforms that are mitogenic to endothelial cells but not to KS spindle cells, suggesting a prevailing paracrine effect of this cytokine. This may be due to the level of expression of the flt-1-VEGF receptor that is down-regulated in KS cells as compared with endothelial cells. KS-derived bFGF and VEGF synergize in inducing endothelial cell growth as shown by studies using both neutralizing antibodies and antisense oligodeoxynucleotides directed against these cytokines. In addition, VEGF and bFGF synergize to induce angiogenic KS-like lesions in nude mice and vascular permeability and edema in guinea pigs. These results indicate that inflammatory cytokines present in KS lesions stimulate the production of bFGF and VEGF, which, in turn, cooperate to induce angiogenesis, edema, and KS lesion formation.

Differential Susceptibility to Activation-Induced Apoptosis Among Peripheral Th1 Subsets: Correlation with Bcl-2 Expression and Consequences for AIDS Pathogenesis

It has been proposed that HIV infection is associated with an imbalance in Th1 and Th2 subsets. Recent reports indicate that Th1 and Th2 effectors differ in their susceptibility to activation-induced apoptosis. To determine whether increased T cell apoptosis in HIV-infected patients contributes to alterations in cytokine synthesis, we performed single-cell analysis of type 1 and type 2 cytokine production by CD4 and CD8 T cells, simultaneously with detection of apoptosis. We demonstrate that a differential alteration in representation of Th1 subsets, rather than commitment of T cells to secrete Th2 cytokines, occurs throughout HIV infection. A significant decrease in the number of IL-2- or TNF-α-producing T cells was observed, whereas those producing IFN-γ remained preserved. Furthermore, there is a gradient of susceptibility to activation-induced apoptosis (IL-2 &lt; IFN-γ &lt; TNF-α) among the different Th1 subsets. This gradient was detected in both CD4 and CD8 subsets, as well as in control donors and HIV-infected patients, in whom the susceptibility to apoptosis of IL-2 and IFN-γ producers was increased compared with controls. This differential intrinsic apoptosis susceptibility of Th1 effectors was found to be tightly regulated by Bcl-2 expression. In HIV-infected persons, disappearance of IL-2-producing T cells was a good indicator of disease progression and was correlated with the progressive shrinkage of the CD4+CD45RA+ T cell compartment and a gradual increased susceptibility to activation-induced apoptosis of the IL-2-producing subset. This close relationship between the CD45RA/CD45R0 ratio, the level of type 1 cytokine production, and susceptibility to apoptosis should be considered in HIV-infected patients under antiviral or immune-based therapies.

Kaposi's sarcoma: a result of the interplay among inflammatory cytokines, angiogenic factors and viral agents

Kaposi's sarcoma (KS) is an angioproliferative disease occurring in 4 clinic-epidemiologic forms. Although the AIDS-associated KS (AIDS-KS) is the most aggressive, all forms of KS share the same immunological and histopathological features suggesting common etiological and pathogenic factors. Recent data indicate that at least in early stage KS is not a real sarcoma but an angiohyperplastic-inflammatory lesion mediated by inflammatory cytokines and angiogenic factors, that is triggered or amplified by infection with human herpesvirus-8. In addition, the human immunodeficiency virus type-1 Tat protein appears to be responsible for the higher grade of aggressiveness of AIDS-KS as compared to the other forms of KS. However, given time, reactive KS may progress to a sarcoma as suggested by evidence of monoclonality in late-nodular lesions.

In vitro production of cytokines in whole blood versus plasma concentrations of cytokines in AIDS

Reports on plasma concentrations of tumor necrosis factor alpha (TFN-alpha), interleukin 6 (IL-6), IL-10, and IFN-alpha in AIDS patients are contradictory. An alternative approach for the estimation of cytokine production is the measurement of lipopolysaccharide (LPS)-stimulated cytokine production in whole blood. We compared plasma concentrations of these cytokines, soluble TNF receptor (sTNFr) types I and II, and LPS-stimulated cytokine production in whole blood from clinically stable AIDS patients (n = 6) and healthy controls (n = 6). The plasma concentrations of TNF-alpha and sTNFr-II were higher in AIDS patients compared with controls (mean [95% CL]: TNF-alpha, 24 [17-31] and 8 [1-16] pg/ml, respectively, p < 0.01; sTNFr-II, 6.8 [4.6-9.0] and 3.2 [2.4-4.0] ng/ml, respectively, p < 0.01). The plasma concentrations of sTNFr-I and IL-10 were not different between AIDS patients and controls. Neither IL-6 nor IFN-alpha was detectable in any plasma sample. LPS-stimulated production in whole blood of TNF-alpha, IL-6, IL-10, and IFN-alpha was not different between AIDS patients and controls at any combination of LPS concentration (0, 0.1, 0.5, 1, 10, 100, and 1000 ng/ml) and duration of stimulation (0, 4, 8, and 24 hr). It is concluded that the plasma concentrations of TNF-alpha and sTNFr-II, but not of IL-6, IL-10, IFN-alpha, and sTNFr-I, are higher in AIDS patients compared with controls. The production of cytokines in LPS-stimulated whole blood does not provide information additional to the measurements of plasma concentrations.

Duodenal biopsies of HIV-infected patients with diarrhoea exhibit epithelial barrier defects but no active secretion

OBJECTIVES

To characterize diarrhoeal mechanisms in HIV-infected patients, epithelial transport and barrier function of the duodenal mucosa was investigated in vitro.

PATIENTS

Twenty-one HIV-seropositive patients (13 asymptomatic and eight with diarrhoea) and 12 controls from an urban referral-based tertiary care centre in Berlin who underwent duodenoscopy.

METHODS

A new miniaturized Ussing chamber allowed measurements on duodenal forceps biopsies. Epithelial barrier function was characterized by alternating current impedance analysis, which allows differentiation of epithelial and subepithelial resistance and by 3H-lactulose and 3H-mannitol flux measurements. Na+-glucose cotransport was quantified as phlorizin-sensitive short circuit current (Isc) and active ion secretion by baseline and bumetanide-sensitive Isc.

RESULTS

Duodenal biopsies from asymptomatic HIV-infected patients were no different from controls, whereas biopsies from HIV-infected patients with diarrhoea showed a decrease in epithelial resistance from 21.2+/-1.9 to 12.9+/-1.3 omega cm2 (P<0.01). Concomitantly, mucosal-to-serosal lactulose flux increased from 0.29+/-0.02 to 0.40+/-0.03 micromol (hcm2) (P<0.01). Phlorizin-sensitive Isc indicating Na+-glucose cotransport, as well as baseline and bumetanide-sensitive Isc indicating active electrogenic chloride secretion were not different between the three groups.

CONCLUSIONS

A miniaturized Ussing device was developed for electrophysiological investigations of duodenal forceps biopsies, which allowed characterization of active ion transport mechanisms and epithelial barrier function. Duodenum of HIV-infected patients with diarrhoea showed no evidence for active ion secretion or Na+-glucose malabsorption, but showed an impaired epithelial barrier function, which could contribute to diarrhoea by a leak flux mechanism.

In vitro transendothelial migration of blood T lymphocytes from HIV-infected individuals

OBJECTIVE

We hypothesized that differential extravasation of circulating CD4+ or CD8+ T lymphocytes contributes to HIV-associated CD8+ lymphocytic alveolitis. Differences in T-cell transendothelial migration may be intrinsic or emerge at sites where vascular endothelium is activated by overexpression of tumor necrosis factor (TNF)-alpha and interferon (IFN)-gamma.

DESIGN

We used an in vitro model of lymphocyte extravasation to assess transendothelial migration of peripheral blood mononuclear cells (PBMC) from HIV-positive individuals. We assayed bronchoalveolar lavage (BAL) fluid from HIV-positive and normal individuals to determine if increased levels of TNF-alpha and IFN-gamma were present in the lungs of HIV-infected individuals.

METHODS

Transendothelial migration was assessed by determining the number and flow cytometric phenotype of PBMC adherent to or migrating across unstimulated or TNF-alpha and IFN-gamma-activated endothelial cell monolayers. We measured BAL fluid cytokine concentrations using standard antigen-capture enzyme-linked immunosorbent assays for TNF-alpha and IFN-gamma.

RESULTS

T cells migrating across unactivated endothelial cells were significantly enriched for CD4+ T cells. Cytokine activation of endothelial cells allowed significantly greater transendothelial migration of CD8+ T cells compared to unactivated endothelial cells. TNF-alpha was increased in BAL fluid from HIV-positive individuals relative to controls.

CONCLUSIONS

These data suggest that, in HIV-positive individuals, CD4+ T cells are migration competent and blood CD8+ T cells do not have enhanced migration competence relative to CD4+ T cells. CD8+ T cell extravasation is aided by TNF-alpha and IFN-gamma-induced endothelial cells activation.

HIV infection alters the production of both type 1 and 2 cytokines but does not induce a polarized type 1 or 2 state

OBJECTIVE

To test the T-helper (TH)1/TH2 cytokine paradigm in HIV infection.

DESIGN AND METHODS

Cytokine profiles in two separate studies of HIV patients and controls are presented: (i) a longitudinal study of HIV patients with CD4 counts > 500 x 10(6)/l tested at three timepoints compared with controls; (ii) a blinded cross-sectional study of controls and patients with high (> 500 x 10(6)/l) and low (< 500 x 10(6)/l) CD4 counts. Peripheral blood mononuclear cells (PBMC) from patients and controls were tested for the production of two type 1 [interleukin (IL)-2, interferon (IFN)-gamma] and two type 2 (IL-4, IL-10) cytokines by enzyme-linked immunosorbent assay. Both spontaneous and mitogen-induced cytokine production was measured.

RESULTS

HIV infection was noted to have the following effects on cytokine production: (i) it led to the in vivo activation of type 2 cytokines in a small group of individuals with high CD4 numbers characterized by the spontaneous release of IL-4 and IL-10. Longitudinal data showed high spontaneous IL-4 and IL-10 to be a consistent feature of the patient group (at each timepoint some patients were high producers) but to be variable in a given individual; (ii) HIV infection impaired the ability of PBMC to respond to stimuli (selected for their ability to optimally induce each cytokine) in terms of IL-2, IL-4 and IL-10 production in patients with both high and low CD4 cell counts; and (iii) conversely, HIV infection led to an overproduction of IFN-gamma in patients with high CD4 counts; patients with low CD4 produced normal levels of IFN-gamma.

CONCLUSIONS

Our observations did not suggest polarization of the type 1/type 2 cytokine profile in HIV patients. Instead, the data suggested more complex changes to type 1/type 2 cytokine patterns in HIV infection than originally proposed by the TH1/TH2 dichotomy.

Host factors in the pathogenesis of HIV disease

Host factors play an important role in determining rates of disease progression in human immunodeficiency virus (HIV)-infected individuals. HIV is able to subvert the host immune system by infecting CD4+ T cells that normally orchestrate immune responses and by inducing the secretion of proinflammatory cytokines that the virus can utilize to its own replicative advantage. The recognition that certain chemokine receptors serve as necessary co-factors for HIV entry into its target cells as well as the fact that ligands for these receptors can modulate the efficiency of HIV infection has expanded the number and scope of host factors that may impact the pathogenesis of HIV disease. This area of investigation will no doubt yield novel therapeutic strategies for intervention in HIV disease; however, caution is warranted in light of the enormous complexity of the pleiotropic cytokine and chemokine networks and the uncertainty inherent in manipulating these systems. HIV-infected long-term non-progressors represent an excellent model to study potential host factors involved in HIV disease pathogenesis. Genetic factors certainly have a major impact on the immune responses mounted by the host. In this regard, a polymorphism in the gene for the HIV co-receptor CC chemokine receptor 5 (CCR5), which serves as a co-receptor for macrophage (M)-tropic strains of HIV, affords a high degree of protection against HIV infection in individuals homozygous for the genetic defect and some degree of protection against disease progression in HIV-infected heterozygotes. HIV-specific immune responses, including cytotoxic T-lymphocyte (CTL) responses and neutralizing antibody responses, also appear to play salutary roles in protecting against disease progression.

Low production of interferon gamma is related to disease progression in HIV infection: evidence from a cohort of 347 HIV-infected individuals

A total of 347 HIV-seropositive individuals attending the Department of Infectious Diseases at Rigshospitalet in Copenhagen and 110 age- and sex-matched healthy controls not at risk for HIV infection were included in this study. Interferon gamma (IFN-gamma) production was measured in whole blood of 223 HIV-seropositive individuals (68 had developed AIDS at enrollment) and 99 healthy sex- and age-matched controls 4.5 hr after challenge with phytohemagglutinin. HIV-infected individuals for whom IFN-gamma production was measured were followed with a median follow-up time of 2.89 years (range, 0.02-4.54 years) from the date of enrollment. Survival analysis was performed considering three different end points: (1) a CD4 count below 100 cells/mm3, (2) an AIDS diagnosis defined according to the 1993 Centers for Disease Control definition, and (3) death. The production of IFN-gamma was highly increased in the blood of HIV-infected individuals without AIDS, but decreased in the blood of AIDS patients (both compared to controls). In the HIV-infected individuals, the total production of IFN-gamma was positively correlated with the number of CD8+ T lymphocytes and with the number of CD16+/CD56+ natural killer cells and negatively correlated with serum levels of beta2-microglobulin. Low levels of IFN-gamma production were associated with an increased risk of experiencing a CD4 count below 100 cells/m3 and death, analyzed in both univariate analysis and in multivariate analysis adjusting for CD4 counts and age. Thus, changes in production of IFN-gamma seem to be truly related to the risk for disease progression in HIV infection.

Characterization of T cell subsets involved in the production of IFN-gamma in asymptomatic HIV-infected patients

Cells capable of interferon (IFN)-gamma synthesis following mitogenic stimulation can be detected and quantified by a recently developed immunofluorescence assay and flow cytometric analysis. The production of IFN-gamma was investigated in a cohort of 20 asymptomatic human immunodeficiency virus (HIV)-seropositive patients with normal numbers of CD4+ lymphocytes, and in 10 healthy subjects. About 60% of asymptomatic stage A1 patients had increased percentages of blood lymphocytes capable of IFN-gamma synthesis, as compared to healthy subjects. The difference reflected the relatively higher numbers of CD8+ cells, in particular the CD8+ T cell subset lacking CD28 antigen expression. The strong correlation between the CD4+/CD8+ ratio and the CD8+CD28+/CD8+CD28- ratio suggests either a role for CD4+ cells in controlling the CD28+ phenotype or a role for CD8+CD28- cells in the decline of CD4+ lymphocytes. The peculiar ability of CD8+CD28- cells to produce high amounts of IFN-gamma, as compared to CD8+CD28+ cells, supports the hypothesis that the CD8+CD28- lymphocytes constitute a population that is functionally distinct from their double-positive counterparts.

Tumor necrosis factor (TNF) induction from monocyte/macrophages by Candida species

Candida albicans was studied for its capacity to induce TNF production from mouse peritoneal macrophages (PM phi). TNF activities in the culture supernatants of Candida-stimulated PM phi and human peripheral blood monocytes were assessed by L 929 bioassay and ELISA respectively. C. albicans induced TNF production from PM phi and human peripheral blood monocytes in a dose-dependent manner. Although the capacity was lesser than live form, heat-killed C. albicans was also found to be capable of stimulating PM phi to induce TNF. The filtered supernatant of 24 h cultured live C. albicans had no effects on TNF production from PM phi. Saccharomyces cerevisiae-extracted mannan, a yeast cell wall antigen, induced TNF production from PM phi in a dose-dependent manner. Thus, the effect of C. albicans on TNF production from PM phi was seemed to be directly related to the presence of the yeast cell wall itself. Compatible with these data, when various candida species (C. albicans, C. tropicalis, C. pseudotropicalis. C. lusitaniae, C. krusei, C. parapsilosis, C. guilliermondii, C. stellatoidea, C. glabrata) and S. cerevisiae were compared to each other, at a concentration of 2 x 10(6) yeast cells/ml from each species, it was observed that TNF inducing capacities varied. Among the species used in this study, C. guilliermondii and C. glabrata, of which the yeast cell size were the smallest ones, were found to be less potent than that of others to induce TNF from PM phi.

Expression of IL-10, IL-4 and interferon-gamma in unstimulated and mitogen-stimulated peripheral blood lymphocytes from HIV-seropositive patients

Infection of immune cells with HIV induces dysregulation of cytokines which may play a vital role in HIV pathogenesis. We analysed the expression of T helper type 1 (Th1) (interferon-gamma (IFN-gamma)) and Th2 (IL-4, IL-10) type cytokines in peripheral blood lymphocytes (PBL) from HIV+ patients. The semiquantitative reverse transcriptase polymerase chain reaction (RT-PCR) analysis revealed that IFN-gamma mRNA in unstimulated PBL was significantly decreased and IL-10 mRNA was significantly upregulated in patients with < 400 CD4+ T cells/mm3 (n = 30) as compared to patients with > 400 CD4+ T cells/mm3 (n = 6) and normal controls (n = 16). In addition, IL-10 mRNA levels were inversely associated with IFN-gamma expression. Similar results were obtained by measuring IL-10 production in the supernatants of PBL cultured in vitro without stimulation by employing an enzyme immunosorbent assay (ELISA). However, the levels of IL-4 and IFN-gamma produced by unstimulated PBL were undetectable by ELISA. Mitogen stimulation of PBL revealed two groups of HIV+ individuals based on IL-10 production. PBL from one set of individuals produced low levels of IL-10 (low IL-10 producers) whereas the other group produced IL-10 comparable to that of normal controls (IL-10 producers). Production of IL-4 was significantly reduced in HIV+ individuals with < 400 CD4+ T cells/mm3 as compared to the normal controls. However, ability to produce IFN-gamma by mitogen-stimulated total PBL and CD4+ purified cells was not impaired in HIV+ individuals. These results suggest that unstimulated and mitogen-stimulated PBL of HIV+ individuals exhibit dysregulation of Th2 type cytokines which may play a role in HIV immunopathogenesis.

Functional discrepancies between tumor necrosis factor and lymphotoxin alpha explained by trimer stability and distinct receptor interactions

Tumor necrosis factor (TNF) and lymphotoxin alpha (LT alpha) are closely related cytokines which bind with nearly identical affinities to the same pair of cell surface receptors, p55 and p75TNFR. Therefore it is assumed that TNF and LT alpha are redundant cytokines. This study, however, demonstrates that TNF and LT alpha differ significantly with regard to their mitogenic and cytotoxic potentials. LT alpha's superior mitogenic effect could be explained by its formation of a more stable trimer. In contrast to the TNF trimer, which disintegrated under physiological conditions into biologically inactive monomers, the LT alpha trimer remained stable for several days. Accordingly, LT alpha more effectively induced fibroblast growth which demands long-term presence of the cytokine. TNF's superior cytotoxicity, which requires only short-term impact of the cytokine, could be attributed to a distinct interaction with the human p55TNFR. This was demonstrated in NIH 3T3 cells transfected with the human p55TNFR, where cytotoxicity is mediated exclusively by the transfected receptor. Although the p55ATNFR had virtually identical affinities for TNF and LT alpha, as defined by Scatchard analysis, it nevertheless discriminated between binding of each cytokine and showed a 200-fold enhanced cytotoxicity mediated by TNF.

Tumor necrosis factor-alpha responses are depressed and interleukin-6 responses unaltered in feline immunodeficiency virus infected cats

Feline immunodeficiency virus (FIV), a lentivirus similar to HIV, causes an acquired immunodeficiency syndrome in cats. Similar to human immunodeficiency virus (HIV), the pathogenesis of FIV is associated with dysregulation of the cytokine network. While alterations in tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) expression have been reported in HIV-infected patients, changes attributable to HIV and those caused by cofactors such as secondary infections cannot always be readily distinguished. This study evaluated the effect of FIV infection on TNF-alpha and IL-6 production in cats not exposed to other potential cofactors such as secondary infections. TNF-alpha and IL-6 activities were evaluated in bronchoalveolar lavage (BAL) cells from FIV-infected and uninfected specific pathogen free (SPF) cats. Supernatants from lipopolysaccharide (LPS)-stimulated BAL cells from uninfected SPF cats had high levels of TNF-alpha and IL-6 activity, while stimulated BAL cell supernatants from FIV-infected SPF cats had significantly lower levels of TNF-alpha but unaltered IL-6 activity. Similarly, Con A/phorbol myristate acetate (PMA) stimulated non-adherent (NA-) peripheral blood mononuclear cells (PBMC) from FIV infected cats synthesized less TNF-alpha than similarly treated NA-PBMC from uninfected cats. Feline immunodeficiency virus could be recovered from the culture supernatants of BAL cells from infected cats by co-cultivation with susceptible lymphocytes. In situ hybridization identified FIV mRNA in a small fraction of alveolar macrophages in the BAL cell cultures.(ABSTRACT TRUNCATED AT 250 WORDS)

Cytokines from activated T cells induce normal endothelial cells to acquire the phenotypic and functional features of AIDS-Kaposi's sarcoma spindle cells

Kaposi's sarcoma (KS) is a proliferative disease of vascular origin particularly frequent in HIV-1-infected homosexual men (AIDS-KS) and characterized by proliferating spindle-shaped cells, angiogenesis, and inflammatory cell infiltration. Previous work has suggested that KS spindle cells are of endothelial cell origin and that chronic immune activation via the release of inflammatory cytokines may cooperate with basic fibroblast growth factor (bFGF) and the HIV-1 Tat protein in the induction and progression of AIDS-KS. Here we show that KS spindle cells have features of activated endothelial cells, and that conditioned media from activated T cells, rich in the same inflammatory cytokines increased in HIV-1-infected individuals, induce normal endothelial cells to acquire the phenotypic and functional features of KS cells. These include (a) acquisition of a similar pattern of cell surface antigen expression; (b) similar proliferative response to bFGF; (c) induction of the responsiveness to the mitogenic effect of extracellular HIV-1 Tat protein that is now able to promote the G1-S transition of endothelial cell cycle; and (d) induction in nude mice of vascular lesions closely resembling early KS as well as the lesions induced by inoculation of KS cells. These results suggest that chronic immune activation, via release of inflammatory cytokines, may play a role in the induction of KS.

Cerebellar granule neurons develop elevated calcium responses when treated with interleukin-6 in culture

In humans, elevated levels of cytokines are associated with several diseases (including HIV infection and Down Syndrome) that result in developmental abnormalities. Overexpression of interleukin-6 (IL-6) in the central nervous system has been shown to cause extensive neuronal abnormality in mice that becomes more evident with maturation. However, it is difficult to separate direct effects of IL-6 on the developing neurons of an intact animal from indirect effects involving effects on other cell types that possess cytokine receptors, such as microglia and astrocytes. We have found that IL-6 treatment of rat cerebellar granule neurons developing in the absence of other cell types in culture results in the persistence of large, depolarization or neurotransmitter-induced calcium transients, that are normally observed only in immature neurons. The cause of this appears to be the persistence of a calcium-induced calcium release (CICR) component of the calcium response to stimulation. This basic abnormality in neuronal development may contribute to the developmental abnormalities associated with human syndromes that involve elevated cytokine levels.

Growth hormone deficiency coupled with hypogonadism in AIDS

Both growth hormone and sex steroid deficiencies are known to affect quality of life adversely. Hypogonadism is not infrequent in patients with AIDS and due mostly to hypothalamic or end-organ failure. The prevalence of GH deficiency is unknown. We report two cases of GH deficiency in AIDS, one of which was associated with gonadotroph failure. The significance of GH deficiency in HIV infection in terms of its potential effects on disease progression is discussed. Further studies are required to assess the prevalence of GH deficiency and to clarify its role in the immunopathogenesis of AIDS.

Increased level of serum HLA class I antigens in HIV infection. Correlation with disease progression

Analysis of (sHLA-I) antigens in a large number of HIV-positive subjects found a significant increase of their level, but did not detect any change in their molecular profile. Monitoring at yearly intervals for four years of the sHLA-I antigen level in 14 HIV-positive subjects with a normal sHLA-I antigen level at study entry showed a significant correlation between progressive increase of sHLA-I antigen level and disease progression. Furthermore, a Kaplan-Meier plot of the frequency of development of AIDS in 34 patients whose cases were followed for 7 years showed that sHLA-I antigen level is a strong predictor of progression to AIDS. Its predictive value is comparable to that of serum beta 2-mu level, greater than that of serum neopterin, and lower than that of CD4+ T-cell percentage. The predictive value of sHLA-I antigen level in combination with serum beta 2-mu level, neopterin level, or CD4+ T-cell percentage is greater than that of each individual variable. These results suggest that measurement of the sHLA-I antigen level may provide useful prognostic information in HIV-positive subjects.

Interferons in the pathogenesis and treatment of human immunodeficiency virus infection

There still remains several unanswered questions concerning the pathogenesis of human immunodeficiency virus (HIV) infection. Interferons (IFNs), as well as other cytokines, are both dysregulated in HIV infection and serve as effector molecules that modulate the replicative capacity of HIV. Acid-labile IFN-alpha, an aberrant form of interferon earlier described in certain autoimmune diseases, has been detected in HIV-infected individuals. Conversely, a deficient expression of IFN-alpha may occur usually associated with HIV disease. Although conflicting findings have been reported on whether IFN-gamma, a product of activated T and natural killer (NK) cells, is elevated in the peripheral blood (PB) compartment, high levels of its expression have been observed in the germinal centers of the lymph nodes during HIV disease. IFN-alpha and IFN-beta have shown potent anti-retroviral effects in several in vitro systems of both acute and chronic HIV infection. These findings have served as the basis of the rationale for their therapeutic application, resulting in some positive effects at least in those patients with relatively high CD4+ T cell counts and healthy immune functions. Furthermore, IFN-alpha has shown important therapeutic effects on HIV-associated Kaposi's sarcoma (KS). Both suppressive and inductive effects on HIV replication in vitro have been described for IFN-gamma, whereas no clear clinical benefits have been reported following its administration to HIV-infected individuals. In conclusion, IFNs are involved in several pathogenic aspects of HIV infection and AIDS, and certain IFNs may serve as important tools to limit the spread of the virus and the progression of disease.

Increased levels of interferon-gamma (IFN-gamma), IL-4 and transforming growth factor-beta (TGF-beta) mRNA expressing blood mononuclear cells in human HIV infection

Evidence has been presented for the involvement of IFN-gamma, IL-4 and TGF-beta in AIDS. Measured plasma levels may, however, poorly reflect in vivo production, since cytokines act auto- and paracrinally and have very short half life in plasma. In situ hybridization with complementary DNA oligonucleotide probes was used to enumerate blood mononuclear cells expressing cytokine messenger RNA (mRNA). HIV-infected patients had elevated blood levels of cells expressing each of the cytokines, with predominance for cells expressing TGF-beta mRNA. All AIDS patients included had elevated numbers of IL-4 mRNA-expressing cells, and levels of cells expressing this cytokine correlated inversely with counts of CD4+ cells in blood, reflecting the involvement of Th2-like cells in later stages of HIV infection. The described approach should be useful in further studies of cytokines in HIV infection and other diseases.

Cytokine stimulation increases intracellular calcium and alters the response to quisqualate in cultured cortical astrocytes

Cytokine levels are elevated in the central nervous system (CNS) in a variety of disorders and may contribute to abnormalities in CNS function associated with the disorders. To begin to understand the mechanisms through which elevated cytokines affect CNS cells, we have examined the effects of cytokines on astrocyte physiology within minutes of application as well as 24 h later. Both standard cultured cortical astrocytes and those induced to further differentiate by pre-treatment with forskolin were examined. Such treated astrocytes may more closely resemble those in brains exhibiting elevated cytokine levels. The cytokine focused upon was interleukin-1-beta (II-1 beta). Gamma-interferon (gamma-IFN) and tumor necrosis factor-alpha (TNF-alpha) were also examined in some studies. Changes in calcium levels produced by acute application of these cytokines were measured. The most pronounced effect was an immediate calcium elevation in response to II-1 beta in the forskolin pre-treated astrocytes. Longer term treatment with IL-1 beta in forskolin pre-treated astrocytes enhanced the calcium response to quisqualate stimulation, a glutamate neurotransmitter receptor agonist. These results suggest that situations that cause chronic changes in cytokine levels and involve astrocytic differentiation, such as chronic CNS infection or Alzheimer's disease, could change astrocytic responses to normal stimuli. Such changes may result in altered astrocytic support of neurons and therefore cause changes in CNS function.

Increased CD11/CD18 expression on the peripheral blood leucocytes of patients with HIV disease: relationship to disease severity

In HIV disease increased adhesion between leucocytes themselves and between leucocytes and endothelium may contribute to cell loss and viral spread. Using a novel method for the preparation of blood leucocytes for flow cytometry, we report increased expression of leucocyte adhesion molecules (LeuCAMs) (CD11/CD18) on peripheral blood leucocytes of patients with HIV disease compared with normal controls. Patients were divided into two groups on the basis of CD4 T lymphocyte numbers (those with > 0.5 x 10(9)/l and those with < 0.2 x 10(9)/l), and assessed for p24 antigen expression, viral load and serum tumour necrosis factor (TNF) levels as well as LeuCAM expression. Patients with < 0.2 x 10(9)/lCD4 cells had more p24 antigen and more HIV infectious virus and more serum TNF than those with > 0.5 x 10(9)/l. Whilst the percentages of only monocytes and polymorphs expressing CD11b were significantly increased in patients with the least CD4 cells, the density of LeuCAMs, expressed as mean fluorescence intensity (MFI), was significantly increased on all leucocytes, with the most significant increases being seen on patients with the fewest CD4 T cells. Our findings are consistent with leucocyte activation by a soluble factor, although we could find no correlation between levels of TNF and LeuCAM expression. The increased expression of adhesion molecules on peripheral blood leucocytes could play a role in the cellular extravasation and aggregation seen in HIV disease.

Interactions between nutrition and infection with human immunodeficiency virus

Nutritional status is severely compromised in persons infected with the human immunodeficiency virus (HIV). One or a combination of several disease-related factors can contribute to substantial weight loss and malnutrition, accelerating the downhill course of the disease. Efforts to prevent weight loss should include early intervention aimed at appetite stimulation, nutritional supplementation with high-calorie, high-protein oral supplements, and diagnosis and treatment of underlying infections and malabsorption. Although enteral or parenteral feedings may be warranted, these forms of nutritional support pose special problems in HIV-infected persons, and the ultimate benefits of these measures are not yet clear. The recent use of pharmacologic agents to stimulate appetite or improve body composition shows promise, but more research is needed before these drugs can be widely recommended as adjuncts to therapy. In general, unproven remedies should be avoided, as their risks may well outweigh their benefits.

In vitro immunotoxicity of +/- 2'-deoxy-3'-thiacytidine, a new anti-HIV agent

The present study compares the in vitro effect of (+/-)-2'-deoxy-3'-thiacytidine (BCH 189) a new synthetic anti-HIV-1 dideoxynucleoside, with 3'-azido-3'-deoxythymidine (AZT) on the immune function of lymphocytes from 10 normal and 12 HIV-1+ patients (CDC II and III). The effect of different doses of BCH 189 and AZT was analysed in vitro on: (i) T cell proliferation after stimulation with concanavalin A (Con A) or anti-CD3 MoAb; (ii) B cell proliferation and immunoglobulin production after stimulation with pokeweed mitogen (PWM); (iii) cytokine production (IL-2, IL-6, GM-CSF, tumour necrosis factor-alpha (TNF-alpha), interferon-gamma (IFN-gamma) from lymphocytes stimulated with anti-CD3 MoAb or phytohaemagglutinin (PHA). BCH 189 inhibited the proliferation of B and T lymphocytes from normal and HIV+ subjects less than AZT; even if lymphocytes from HIV+ (CDC III) subjects produced higher levels of IL-6 and TNF-alpha, neither BCH 189 nor AZT molecule interfered with cytokine release. Immunoglobulin production from B lymphocytes was inhibited only by a high concentration (50 microM) of BCH 189 or AZT. These results show that BCH 189 affects lymphocyte proliferation in vitro less than AZT, and support its use in clinical trials in HIV-infected patients.

Differences in cytokine secretion by intestinal mononuclear cells, peripheral blood monocytes and alveolar macrophages from HIV-infected patients

Mononuclear cells of the lamina propria (LpMNC), isolated from endoscopically taken biopsies of the large bowel from AIDS patients, were analysed for their ability to secrete tumour necrosis factor-alpha (TNF-alpha), IL-1 beta and IL-6. Stimulation of LpMNC from normal controls with pokeweed mitogen (PWM) led to a time- and dose-dependent enhancement of TNF-alpha, IL-1 beta and IL-6 secretion. In contrast, PWM stimulation of LpMNC from AIDS patients resulted in only a small increase in TNF-alpha release. Constitutive secretion of IL-1 beta and IL-6 in these patients was already increased to the concentration range of stimulated cells from normal controls and could not be further increased, probably due to maximal in vivo stimulation. Secretion of TNF-alpha, IL-1 beta and IL-6 by peripheral blood monocytes (PBM) and alveolar macrophages from AIDS patients was elevated with or without stimulation compared with normal controls. Obviously, the regulation of TNF-alpha secretion is dependent on the microenvironment. Since it is known that interferon-gamma (IFN-gamma) may induce the production of TNF-alpha, the secretion of this cytokine was examined. Release of IFN-gamma was constitutively and under stimulation lowered in LpMNC from AIDS patients compared with normal controls. Addition of IFN-gamma to LpMNC did not result in enhanced TNF-alpha secretion. Our data indicate a defective function of intestinal mononuclear cells in AIDS patients as shown by the diminished TNF-alpha secretion.