Lack of evidence for the dichotomy of TH1 and TH2 predominance in HIV-infected individuals

Coreceptor/Chemokine Receptor Expression on Human Hematopoietic Cells: Biological Implications for Human Immunodeficiency Virus–Type 1 Infection

The recent discovery of chemokine receptors as coreceptors for human immunodeficiency virus–type 1 (HIV-1) entry offers new avenues for investigating the pathogenesis of acquired immunodeficiency syndrome (AIDS)-related cytopenias. To this end, we sought to (1) phenotype human hematopoietic cells for CD4 and the HIV-1 coreceptors CXCR4, CCR5, CCR3, and CCR2b; (2) correlate CD4 and chemokine receptor expression with their susceptibility to HIV-1 infection; and (3) examine any potential interplay between inflammatory cytokines released during HIV-1 infection and regulation of chemokine receptor expression. Fluorescence-activated cell sorting (FACS) analysis of bone marrow mononuclear cells (BMMNC), cells derived from serum-free expanded hematopoietic lineages (colony-forming unit–granulocyte-macrophage [CFU-GM], colony-forming unit-megakaryocyte [CFU-Meg], and burst-forming unit-erythroid [BFU-E]), and CD34+ cells showed differential expression of chemokine receptors and CD4 with some lineage specificity. Significantly, FACS-sorted CXCR4+/CD34+ cells had the same clonogeneic potential as CXCR4−/CD34+ cells. Reverse transcriptase-polymerase chain reaction (RT-PCR) analysis of FACS-sorted human candidate stem cells (HSC; CD34+, c-kit+, Rho123low) showed the presence of CXCR4 mRNA but not CD4 mRNA. Infection studies with HIV-1 Env-pseudotyped luciferase reporter viruses indicated that X4 Env (CXCR4-using) pseudotypes infected megakaryocytic cells, whereas R5 Env (CCR5-using) pseudotypes did not. Similarly, R5 but not X4 Env-pseudotyped viruses infected granulocyte-macrophage cells in a CD4/CCR5-dependent manner. Erythroid cells were resistant to R5 or X4 viral infection. Finally, we found that γ-interferon treatment upregulated CXCR4 expression on primary hematopoietic cells. In summary, the delineation of chemokine receptor expression on primary hematopoietic cells is a first step towards dissecting the chemokine-chemokine receptor axes that may play a role in hematopoietic cell proliferation and homing. Furthermore, susceptibility of hematopoietic cells to HIV-1 infection is likely to be more complicated than the mere physical presence of CD4 and the cognate chemokine receptor. Lastly, our results suggest a potential interplay between γ-interferon secretion and CXCR4 expression.

Differential expression profiles of apoptosis-affecting genes in HIV-infected cell lines and patient T cells

OBJECTIVE

To clarify the molecular mechanisms of HIV-induced apoptosis.

DESIGN

The assessment of expression patterns for genes affecting the interrelated cell cycle and apoptosis processes in HIV-1LAI-infected T lymph oblastoid (CEM) cells, as well as CD4 and CD8 cells from HIV-infected individuals and controls.

METHODS

The kinetics of HIV infection in CEM cells were defined by flow cytometry of green fluorescent protein expression from a reporter vector. Apoptosis of CEM cells was measured by propidium iodine staining and flow cytometry. Gene expression levels were determined by a multiprobe RNase protection assay.

RESULTS

The infection and apoptosis of CEM cells were associated with enhanced expression of Bax, Bcl-2, Bcl-X(L) and caspase 1 (ICE). There was increased expression of Bcl-2 and caspase 1 and decreased expression of cyclin-dependent kinase inhibitor p21CIP1 in CD4 cells of HIV-infected individuals compared with uninfected controls. The CD8 cells of HIV-infected individuals exhibited increased expression of Bcl-2, Bcl-X(L), Bax and caspase 1 but, in contrast to the CD4 subset, they showed elevated expression of p21CIP1 and p16INK4a compared with controls.

CONCLUSIONS

The Bax increase in CEM cells appears to be a direct effect associated with a high frequency of infection and apoptosis, because it was not found in the CD4 cells of patients. In contrast, the increase of Bax in the CD8 cells of patients seems to be an indirect effect. Increases in Bcl-2, Bcl-X(L) and caspase 1 in HIV-infected CEM cells may be caused by both direct and indirect mechanisms, because they also occurred in CD4 and CD8 cells of HIV-infected individuals. In addition, the low expression of p21CIP1 in the CD4 subset of HIV-infected individuals could promote apoptosis, whereas the high expression of p21CIP1 and p16INK4a in the CD8 subset may lead to a state of anergy, akin to replicative senescence.

Functional Fas-ligand expression on T cells from HIV-1-infected patients is unrelated to CD4+ lymphopenia

Recent studies have demonstrated that the expression of Fas by peripheral T cells from HIV-1+ patients is deregulated and increases the susceptibility of these cells to undergo apoptosis. Here, we show that secretion of Fas-ligand (L), the complementary agonist of Fas, is abnormally upregulated in CD4+ cells from HIV-1-infected individuals, particularly during the non-lymphopenic stages of the disease. An increase of soluble Fas-L occurred in T cell cultures from 26 patients with a number of CD4+ cells higher than 400/microliter, whereas it was almost undetectable in cultures from 21 severely lymphopenic patients (CD4+ < 200/microliter). The MTT test, cytofluorimetric analysis of cellular DNA, cytotoxicity, and proliferative assays using the Fas-transfected WC8 mouse lymphoma confirmed the cytocidal capability of T cell supernatants from non-lymphopenic patients. Double-fluorescence analysis revealed that the majority of CD4+ cells (approximately 90%) in these cultures secreted Fas-L in the presence of high intracellular gamma-interferon and low Bcl-2. In contrast, the CD8+/Fas-L+ population was comparably decreased (approximately 55%). Molecular cloning of Fas-L revealed a substantial expression of Fas-L mRNA in cells from non-lymphopenic patients compared with patients with advanced disease and healthy controls. Since CD4+ cells of Th1 phenotype are impaired during HIV-1 infection and show high cellular expression of Fas-L, it is conceivable that excess Fas-L during the early or non-lymphopenic phase of the disease increases the extent of apoptosis in these cells by the Fas/Fas-L pathway. The defective expression of the ligand in severely lymphopenic stages could be explained by exhaustion of this mechanism as the disease progresses.

Effect of protease therapy on cytokine secretion by peripheral blood mononuclear cells (PBMC) from HIV-infected subjects

The viral load reduction seen in patients with late stage HIV infection treated with the protease inhibitor, ritonavir, is accompanied by increases in the in vitro proliferative responses generated by PBMC. The present study was undertaken to investigate which lymphocyte subsets generated these responses and the effects of therapy on cytokine production. Lymphoproliferation following phytohaemagglutinin (PHA) stimulation was studied by thymidine incorporation, and production of IL-2, interferon-gamma (IFN-gamma) and IL-4 was assessed by ELISA in 12 patients receiving ritonavir and seven receiving placebo in the context of randomized, blinded clinical trials. CD4+ cell-depleted and CD8+ cell-depleted subsets were obtained from PBMC by immunomagnetic bead depletion. At week 4 of therapy a two-fold or greater increase in proliferative responses was observed in 9/12 subjects receiving therapy, compared with 0/7 receiving placebo. Similarly there was a significant increase in IL-2 and IFN-gamma production of 2.7-fold (P = 0.02) and 1.7-fold (P = 0.03), respectively, in the treatment group compared with those receiving placebo. No change in IL-4 production was observed. Despite these increases, cytokine responses post-therapy were still reduced compared with both healthy controls and asymptomatic HIV-infected subjects. Increases in proliferative response and IL-2 production were greater in the CD8+ cell-depleted population than in the CD4+ cell-depleted population, whereas increases in IFN-gamma production were derived from the CD4+ cell-depleted population.

Reduced production of both Th1 and Tc1 lymphocyte subsets in atopic dermatitis (AD)

An imbalance of interferon-gamma (IFN-gamma)-bearing CD4+ T (Th1) cells in the pathogenesis of AD is well recognized; however, a possible role in AD for CD8+ T cells secreting Th1-like cytokines (Tc1) has not been properly addressed. In this study, two- and three-colour FACS analysis allowed us to discriminate the Th1 from the Tc1 subset. AD patients had half the number of IFN-gamma-producing circulating T cells (P < 0.005; 13.6 +/- 1.9% (mean +/- s.d.)) compared with normal donors (25.0 +/- 2.4%). Specifically, both Th1 (4.8 +/- 0.7%) and Tc1 (8.1 +/- 1.1%) cells in AD were decreased compared with Th1 (8.8 +/- 0.8%) and Tc1 (15.0 +/- 1.5%) cells in controls. Moreover, at the mRNA level, the ratios of IFN-gamma/IL-4 and IFN-gamma/IL-10 were lower in cells from AD patients compared with controls. In conclusion, the decrease of IFN-gamma-producing T lymphocytes in AD is due to a reduction in both Th1 and Tc1 IFN-gamma-secreting cells; this may not only contribute to the over-production of IgE, but also explain the high incidence of cutaneous infections observed in AD patients.

Expression of inducible nitric oxide synthase in human granulomas and histiocytic reactions

Inducible nitric oxide synthase (iNOS) is required in immune response against infections and is involved in granuloma formation in animals; in murine macrophages, iNOS is induced by lipopolysaccharide and interferon-gamma. In contrast, the role of iNOS in human immune response against infections is still questioned, and its expression in granulomas is poorly investigated. Using Western blotting and immunohistochemistry, we investigated iNOS expression in human lymph nodes with nonspecific reactions and in tissues containing granulomas caused by mycobacteria, Toxoplasma, Cryptococcus neoformans, Leishmania, Bartonella, noninfectious granulomas (sarcoidosis, foreign body), and other hystiocitic reactions (Kikuchi's disease, Omenn syndrome). iNOS was undetectable in nonspecific reactive lymphadenitis, foreign-body granulomas, and Omenn syndrome, whereas it was strongly expressed in infectious granulomas, sarcoidosis, and Kikuchi's diseases. Immunohistochemistry demonstrated that iNOS was selectively expressed by the epithelioid and multinucleated giant cells within the granulomas. Use of an anti-nitrotyrosine antibody, recognizing nitrosilated amino acid residues derived from nitric oxide production, revealed a consistent positivity within the cells expressing iNOS, thus suggesting that iNOS is functionally active. Detection of cytokines by reverse transcriptase-polymerase chain reaction demonstrated that tissues that were positive for iNOS, also expressed the Thl-type cytokine interferon-gamma mRNA, but not the Th2-type cytokine interleukin-4. Taken together, these results indicate that iNOS is involved in different human immune reactions characterized by histiocytic/granulomatous inflammation and associated with Th1-type cytokine secretion.

Determinant in human immunodeficiency virus type 1 for efficient replication under cytokine-induced CD4(+) T-helper 1 (Th1)- and Th2-type conditions

Cytokines are potent stimuli for CD4(+)-T-cell differentiation. Among them, interleukin-12 (IL-12) and IL-4 induce naive CD4(+) T cells to become T-helper 1 (Th1) or Th2 cells, respectively. In this study we found that macrophage-tropic human immunodeficiency virus type 1 (HIV-1) strains replicated more efficiently in IL-12-induced Th1-type cultures derived from normal CD4(+) T cells than did T-cell-line-tropic (T-tropic) strains. In contrast, T-tropic strains preferentially infected IL-4-induced Th2-type cultures derived from the same donor CD4(+) T cells. Additional studies using chimeric viruses demonstrated that the V3 region of HIV-1 gp120 was the principal determinant for efficiency of replication. Cell fusion analysis showed that cells expressing envelope protein from a T-tropic strain effectively fused with IL-4-induced Th2-type culture cells. Flow cytometric analysis showed that the level of CCR5 expression was higher on IL-12-induced Th1-type culture cells, whereas CXCR4 was highly expressed on IL-4-induced Th2-type culture cells, although a low level of CXCR4 expression was observed on IL-12-induced Th1-type culture cells. These results indicate that HIV-1 isolates exhibit differences in the ability to infect CD4(+)-T-cell subsets such as Th1 or Th2 cells and that this difference may partly correlate with the expression of particular chemokine receptors on these cells. The findings suggest that immunological conditions are one of the factors responsible for inducing selection of HIV-1 strains.

Diverse host responses and outcomes following simian immunodeficiency virus SIVmac239 infection in sooty mangabeys and rhesus macaques

Sooty mangabeys naturally infected with simian immunodeficiency virus (SIV) do not develop immunodeficiency despite the presence of viral loads of 10(5) to 10(7) RNA copies/ml. To investigate the basis of apathogenic SIV infection in sooty mangabeys, three sooty mangabeys and three rhesus macaques were inoculated intravenously with SIVmac239 and evaluated longitudinally for 1 year. SIVmac239 infection of sooty mangabeys resulted in 2- to 4-log-lower viral loads than in macaques and did not reproduce the high viral loads observed in natural SIVsmm infection. During acute SIV infection, polyclonal cytotoxic T-lymphocyte (CTL) activity coincident with decline in peak plasma viremia was observed in both macaques and mangabeys; 8 to 20 weeks later, CTL activity declined in the macaques but was sustained and broadly directed in the mangabeys. Neutralizing antibodies to SIVmac239 were detected in the macaques but not the mangabeys. Differences in expression of CD38 on CD8(+) T lymphocytes or in the percentage of naive phenotype T cells expressing CD45RA and CD62L-selection did not correlate with development of AIDS in rhesus macaques. In macaques, the proportion of CD4(+) T lymphocytes expressing CD25 declined during SIV infection, while in mangabeys, CD25-expressing CD4(+) T lymphocytes increased. Longitudinal evaluation of cytokine secretion by flow cytometric analysis of unstimulated lymphocytes revealed elevation of interleukin-2 and gamma interferon in a macaque and only interleukin-10 in a concurrently infected mangabey during acute SIV infection. Differences in host responses following experimental SIVmac239 infection may be associated with the divergent outcome in sooty mangabeys and rhesus macaques.

Th1/Th2 cytokine expression in saliva of HIV-positive and HIV-negative individuals: a pilot study in HIV-positive individuals with oropharyngeal candidiasis

Current data suggest that T-helper (Th)2-type cytokine responses are often associated with progression to AIDS in HIV-positive individuals. Similarly, Th2-type cytokines are associated with susceptibility to mucosal candidiasis, of which oropharyngeal candidiasis (OPC) is one of the most common opportunistic infections in HIV-positive individuals. Although little information is available on host defense mechanisms at the level of the oral mucosa, recent studies suggest that local cell-mediated immunity (CMI) is equally or more important than that in the periphery for host defense against mucosal Candida albicans infections. This study investigated the potential presence of oral-associated CMI through the expression of Th1/Th2-type cytokines in saliva of immunocompetent and immunocompromised individuals with and without OPC. Results showed a constitutive mixed Th1/Th2 cytokine expression (Th0) in whole saliva of healthy HIV-negative individuals. In contrast, HIV-positive individuals had a dominant Th2-type salivary cytokine profile (interleukin-4 [IL-4], IL-10) (IL-2, interferon-y [IFN-gamma], IL-12) that seemingly resulted from a lack of Th1-type cytokines rather than enhanced Th2-type cytokines. Moreover, pilot analyses of those with OPC showed evidence for a more profound salivary Th2-type profile. Both HIV-positive and HIV-negative patients, irrespective of CD4 counts, had some level of positive in vitro systemic lymphocyte proliferative responses to C albicans antigens. These results suggest that the Th1/Th2 cytokine dichotomy in HIV disease is detectable in situ in oral secretions and may be a useful indicator of oral-associated CMI to better understand resistance/susceptibility of HIV-positive individuals to oral opportunistic infections, including OPC.

Cytokine response in multiple lymphoid tissues during the primary phase of feline immunodeficiency virus infection

Type 1 and 2 cytokine mRNA responses were measured at various time periods and in various lymphoid compartments during the acute stage (first 4 months) of feline immunodeficiency virus (FIV) infection in laboratory cats. Cytokine responses were correlated with virus replication. Virus was detected in plasma and tissue from day 14 postinfection (p.i.) onward, peaked at 56 to 70 days, and declined greatly by 70 days. Virus replication was highest in the thymus, followed by spleen, mesenteric lymph nodes, and cervical lymph nodes. Baseline cytokine levels were highest in the mesenteric lymph nodes and lowest in the cervical lymph nodes. Cytokine upregulation after FIV infection was most dramatic in the cervical lymph nodes, with the greatest increase in interleukin-10 (IL-10) and gamma interferon (IFN-gamma). Cytokine transcription in the mesenteric lymph node increased above baseline by day 14 p.i. for IFN-gamma, IL-12p40, IL-4, and IL-10, while elevations in the spleen were mainly for IFN-gamma, IL-12p40 and IL-10. An increase in IFN-gamma, IL-10, and IL-12p40 occurred in the thymus at day 56 p.i., concomitant with the onset of thymitis. In general, type 2 cytokines (IL-4 and IL-10) were increased greater than 1 log over baseline, while the elevations in type 1 cytokines were less than 1 log. In the tissues tested, CD4(+) cells were the primary source of IL-2, IL-4, and IL-10. Both CD4(+) and CD8(+) cells produced IFN-gamma, while no cytokine mRNA was detected in B cells. These results demonstrate the presence of a heterogeneous cytokine response in lymphoid tissues during the primary stage of FIV infection. The nature and intensity of the response differed from one compartment to the other and, in the case of the thymus, also with inflammatory changes. Although limited in scope, the present study confirms the usefulness of the FIV infection model in studying early cytokine events that lead to the secondary subclinical carrier state typical of most lentivirus infections.

Dynamics of serum cytokines in patients with visceral leishmaniasis and HIV-1 co-infection

Serum cytokine levels and peripheral T cell subpopulations of HIV-1-infected patients before, during and after active visceral leishmaniasis (VL) were analysed and compared with appropriate controls. At VL diagnosis, co-infected patients showed higher serum levels of interferon-gamma (IFN-gamma) than matched HIV-1 controls without VL, and lower serum concentrations of IL-10 than non-immunocompromised VL controls. High levels of tumour necrosis factor-alpha (TNF-alpha) and IFN-gamma were present in the sera of HIV-1-infected patients with active VL. TNF-alpha remained elevated after VL recovery. A steady decline in the CD4+ cell count, an increase of serum HIV viraemia and a progressive seroconversion for the HIV-1 p24 antigen was observed during the course of VL disease. Thus, an aberrant activation of the TNF system with possible negative immunological and virological consequences is present in HIV-1-infected patients with VL. A more extensive prospective validation of these findings in a bigger cohort of patients will nevertheless be necessary. The results support the hypothesis that different opportunistic infection agents may trigger the production of proinflammatory cytokines during immunodeficiency, and in this way accelerate the course of HIV-1 disease.

Evidence for a role of T-helper type 2 cytokines in the acquisition of human immunodeficiency virus syncytium-inducing phenotype

BACKGROUND

The objective of the present study was to investigate the relationship between the serum cytokine pattern of T-helper (Th) response and the acquisition of syncytium-inducing (SI) human immunodeficiency virus type 1 (HIV-1) variants in HIV-1-seropositive patients treated with antiretroviral drugs.

METHODS

Serum cytokines of Th1/Th2 responses were analysed in a case-control study of 20 individuals selected from a cohort of HIV-1-infected patients without SI variants at entry, who developed or did not develop SI virus during a prospective follow-up. A group of 10 patients with SI variants at study entry was also evaluated. Serum concentration of interferon (IFN) gamma, interleukin (IL) 2, IL-4 and IL-10 was evaluated by mean of a commercial enzyme immunoassay.

RESULTS

Despite close matching for immunological (CD4+ cell count) and virological (p24 antigen, serum HIV viraemia) parameters, SI-converting patients showed at baseline significantly lower serum levels of IL-2 and higher concentrations of IL-4 than those who remained persistently negative for SI variants. Shortly after the phenotype conversion, SI-converting patients were characterized by significantly high serum concentration of IL-4 and by low levels of IFN-gamma (Th2-like pattern). Patients with SI phenotype at study entry featured lower mean levels of both IL-4 and IL-10, but mean IFN-gamma and IL-2 values were higher, although the clinical and immunological baseline was also poorer and no statistical analysis could be applied.

CONCLUSION

Serum cytokine pattern of Th1/Th2 response differs between patients with NSI and SI phenotype. Our data strongly suggest that the Th2 cytokine pattern could be associated with the acquisition of the SI HIV-1 phenotype.

IL-2 and IFN-gamma, but not IL-4 secretion by peripheral blood mononuclear cells (PBMC) are related to CD4+ T cells and clinical status in Brazilian HIV-1-infected subjects

It has been reported that production of IL-2 and IFN-gamma, known as T-helper type 1 cytokines, by peripheral mononuclear cells (PBMC) decreases with progression of HIV infection. In contrast, IL-4 and IL-10 production, Th2 cytokine profile, increases with HIV disease progression. PBMC were evaluated from 55 HIV-infected subjects from Divisão de Imunologia, Hospital das Clínicas, Faculdade de Medicina da Universidade de São Paulo, to "in vitro" cytokines production after 24 hours of stimulation with PHA. Low levels of IL-4 production in both HIV-infected patients and normal subjects, were detected. The patients with CD4+ T cell counts < 200 showed a significant decrease of IL-2 and IFN-gamma production compared to controls. Patients with higher counts of CD4+ T cells (either between 200-500 or > 500 cells/mm3) also showed decreased production of IL-2 that was not statistically significant. There was a correlation between IL-2 and IFN-gamma release with CD4+ T cells counts. HIV-1-infected individuals with CD4+ T cells > 500 cells/mm3 showed increased levels of IL-2 and IFN-gamma, than individuals with CD4+ T cells < 500 cells/mm3. In conclusion, we observed a decline of IL-2 and IFN-gamma production at advanced HIV disease. IL-4 production was not affected during HIV infection. Taken together, these findings suggest that the cytokine profile might be influenced by the HIV infection rather than the cause of disease progression.

Protein levels of interleukin-12 p70 holomer, its p40 chain and interferon-gamma during advancing HIV infection

BACKGROUND

a switch from T helper 1 (TH1) to T helper 2 (TH2)-like cytokine production has been proposed for progressive HIV infection.

OBJECTIVE

to study whether this hypothesis is reflected by altered IL-12 and IFN-gamma serum levels in HIV patients.

METHODS

we measured serum levels of IL-12 p40 and p70 and IFN-gamma in 90 HIV seropositive patients at differing disease stages and in 10 healthy controls by radioimmunoassays. These cytokines were compared to established surrogate markers of immunodeficiency.

RESULTS

IFN-gamma, as well as IL-12 p40 and p70, levels were significantly increased in HIV patients compared to controls. However, IFN-gamma and IL-12 showed no significant variations with progressive stages of immunodeficiency. IFN-gamma levels showed a significant positive correlation to the progression marker beta2-microglobulin and correlated negatively with CD4+ lymphocyte counts. In addition, IFN-gamma concentrations were related to sTNF-R p55 and p75 serum levels. Interestingly. IFN-gamma was related to IL-12 only with respect to p40, but not to p70.

CONCLUSIONS

although our data do not necessarily reflect cytokine secretion at the single cell level or the cytokine milieu in the lymphoid microenvironment, our results from peripheral blood fail to demonstrate progressively decreased IL-12 and IFN-gamma serum levels in HIV infected patients.

Consequences of ddI-induced reduction of acute SIVmac251 virus load on cytokine profiles in cynomolgus macaques

This study evaluates the consequences of antiretroviral treatment of the acute simian immunodeficiency virus (SIV) primary infection on virus load and cytokine responses. Four cynomolgus macaques were inoculated intravenously with a pathogenic primary isolate (SIVmac251). Animals were pretreated with 10.8 mg/kg/day of dideoxyinosine (ddI) from 4 days before inoculation, and treatment was continued for 28 days. Proinflammatory (IL6, IL1 beta and TNF alpha) and antiinflammatory (IL10) cytokine and lymphokine (IL2, IL4 and IFN gamma) polymerase chain reaction (PCR) ratios were monitored in unmanipulated peripheral blood mononuclear cells (PBMCs) during acute infection by using a semiquantitative reverse transcription (RT)-PCR method. PBMC-associated virus loads were dramatically reduced compared to those of placebo-treated macaques. Nevertheless, a transient rise in IL6, IL1 beta, TNF alpha and IL10 mRNA expression was observed in PBMCs. IL2, IL4 and IFN gamma mRNAs were either undetectable or weakly detectable throughout the study, with no major changes. Despite a dramatic reduction in the acute viral loads in ddI-treated monkeys, early cytokine mRNA profiles were comparable to those of untreated SIVmac251-infected monkeys. Contrary to what was previously evidenced during primary infection with an attenuated SIV clone, no increase in IL2 and IL4 mRNA was detected in PBMCs of the ddI-treated monkeys, although these monkeys exhibited virus loads similar to those evidenced in macaques infected by attenuated SIV. These data indicate that differential lymphokine expression patterns found in pathogenic and Nef-truncated SIV-infected monkeys may not be strictly dependent on virus load levels.

Segregation of type 1 cytokine production in human peripheral blood lymphocytes: phenotypic differences between IFN-gamma and IL-2-producing cells in the CD8+ T cell subset

T cell clones are classified as type 0, 1 or 2 depending on the lymphokines they produce. However, it has remained unclear whether single cells of a given type produce one or several cytokine species. Flow cytometric analysis of peripheral blood lymphocytes (PBL) obtained from 20 healthy donors for the production of the type 1 cytokines IFN-gamma and IL-2 revealed very few cells that co-expressed both cytokines independently of the mitogenic stimulus used for PBL activation. Similarly, kinetic studies of cytokine synthesis indicated a low percentage of IFN-gamma/IL-2 double-positive T cells at all time points. Reverse transcription-PCR analysis of sorted IL-2- and IFN-gamma-positive T cells showed the presence of IL-2- or IFN-gamma-specific mRNA only in those cells expressing the corresponding cytokine. This segregation of the two type 1 cytokines was lost in long-term cultured T cells and in T cell clones. A high percentage of cells expressing only IL-2 or IFN-gamma was observed even when the production of these cytokines was evaluated on CD4- and CD8+ subsets. Moreover, in some healthy individuals, IFN-gamma and IL-2 production by CD8+ T cells was related to CD8+ expression levels and cell size, i. e. IL-2-expressing cells were generally smaller with more intense CD8+ staining as compared with IFN-gamma-producing T cells. These data indicate that activated T lymphocytes are strongly committed in vivo to produce IFN-gamma or IL-2 and emphasizes the independent regulation of the two cytokine genes.

Differential production of IL-10 by T cells and monocytes of HIV-infected individuals: association of IL-10 production with CD28-mediated immune responsiveness

Immune unresponsiveness in HIV-1 infection can result from impaired signals delivered by the costimulatory CD28-B7 pathway and the altered production of immunoregulatory cytokines, in particular IL-10, whose production is altered in HIV-1 infection. In this study we investigate IL-10 regulation in T cells and monocytes from HIV+ individuals, and its association with CD28-mediated T cell proliferation. IL-10 production as analysed in T cell- and monocyte-depleted peripheral blood mononuclear cells (PBMC), and by intracellular staining at the single-cell level, reveals a defect in IL-10 production by CD4+ and CD8+ T cells, whereas monocytes constitute the major IL-10-producing cell type. To investigate the impact of IL-10 on immune responsiveness, CD28-mediated proliferative responses in HIV+ individuals were correlated with PHA-induced IL-10 production. CD4+ T cells expressed CD28, yet exhibited markedly reduced CD28-mediated cell proliferation. This CD28-mediated CD4+ T cell proliferation was found to be inversely associated with the levels of PHA-induced IL-10 production and could be restored, at least in part, by anti-IL-10 antibodies. These results suggest that IL-10 production is differentially regulated in T cells and monocytes of HIV+ individuals, and that IL-10 may have a role in inducing immune unresponsiveness by modulating the CD28-B7 pathway.

Enhanced HIV expression during Th2-oriented responses explained by the opposite regulatory effect of IL-4 and IFN-gamma of fusin/CXCR4

The human alpha-chemokine receptor fusin/CXCR4 is an important cofactor for entry of T lymphocyte-tropic HIV-1 strains. We investigated the possible regulatory role of T cell cytokine patterns on CXCR4 as well as HIV expression by using in vitro models of both secondary and primary immune responses. Antigen-specific memory CD4+ T cells infected with a T-tropic HIV-1 strain showed significantly higher CXCR4 and HIV-1 expression in Th0/2-oriented responses in comparison with Th1-oriented responses. Similarly, in naive CD4+ T cells activated in the presence of IL-4 or IL-12 and infected with the same T-tropic strain, IL-4 up-regulated whereas IL-12 down-regulated both CXCR4 and HIV-1 expression. The down-regulatory effect of IL-12 on CXCR4 expression was found to be dependent on its capacity to induce IFN-gamma production. These observations can account for the higher risk of progression in HIV-1-infected individuals undergoing Th0/2-oriented immune responses.

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.

T cell responses in coinfection with Onchocerca volvulus and the human immunodeficiency virus type 1

Onchocerca volvulus and the human immunodeficiency virus (HIV) are two immunocompromising infectious agents of major public health concern in Uganda. To examine the effect of coinfection with O. volvulus and HIV on cellular immune responses, lymphocyte proliferative responses and cytokine production of peripheral blood mononuclear cells (PBMC) from persons infected with O. volvulus with and without HIV type 1 infection were compared. Proliferation of PBMC to PHA and tuberculin (PPD) in coinfection was less (P = 0.08, P < 0.01) than in O. volvulus infection. O. volvulus extract stimulated lymphocyte proliferation in microfilaria-negative and HIV-negative O. volvulus infection while only an inconspicuous response was observed in microfilaria-negative coinfection. After stimulation of PBMC with PPD, the production of interferon-gamma (IFN-gamma), interleukin (IL)-4 and IL-5-demonstrated in O. volvulus infection-were reduced in coinfection with HIV (P < 0.01). While both groups failed to produce IFN-gamma in response to O. volvulus extract, only O. volvulus infected persons generated pronounced IL-5 and low IL-4 levels (0.01 > P = 0.02). The cellular immune responses in coinfection suggested an HIV-related lack of specific reactivity to O. volvulus antigen and impairment of IL-4 and IL-5 production in addition to the lack of IFN-gamma response on antigenic stimulation.

Early reduction of immune activation in lymphoid tissue following highly active HIV therapy

OBJECTIVE

To evaluate immune reconstitution within HIV-infected lymphoid tissue during highly active antiretroviral therapy (HAART).

DESIGN AND METHODS

In situ cellular responses were studied in sequential tonsillar biopsies in three asymptomatic HIV-infected (CD4 cells greater than 400 x 10(6)/l) antiretroviral treatment-naive volunteers enrolled in a clinical trial to determine the early effect of HAART. Computerized image analysis was used to study immunohistochemically stained sequential tonsil sections for the patterns of local cytokine production, chemokine receptor expression and cellular distribution. Replicate quantitative assessments of samples before and after 4 weeks of therapy were used for the evaluation of drug effects and compared with four uninfected controls. Tonsillar HIV proviral-DNA was determined by fluorescent in situ 5'-nuclease assay.

RESULTS

HIV-infected tonsil tissue was characterized by extensive pro-inflammatory and type 1 cytokine expression. A five- to 15-fold elevation of interleukin (IL)-1 alpha, IL-12, IL-2 and interferon (IFN)-gamma protein expression was found compared with controls, and each encompassed a mean of at least 4.5% of the tissue compartment. This was reduced by 20-90% in all individuals after 4 weeks of HAART. In contrast, type 2 cytokine expression (IL-4, IL-10), plus tumour necrosis factor (TNF)-alpha, remained low throughout the study. HAART reduced, by 40%, the expression of HIV co-receptors, CCR5 and CXCR4, which initially were elevated four to six times over the control values. In addition, the myelomonocytic inflammatory proteins, CD68 and calprotectin, diminished by 26-83% after therapy. The HIV RNA was reduced to undetectable levels in plasma by HAART. However, a large pool of tonsil cells (2-7%), remained HIV DNA positive after 4 weeks of therapy.

CONCLUSIONS

Although immune activation may be the direct consequence of HIV replication, HAART-associated reconstitution begins with a reduction in inflammatory cytokine production which precedes the elimination of local proviral reservoirs.

Dual effect of interleukin 4 on HIV-1 expression: implications for viral phenotypic switch and disease progression

We report that interleukin 4 (IL-4) inhibits the propagation of non-syncytia-inducing and increases the propagation of syncytia-inducing HIV-1 isolates by two mechanisms. It differentially regulates the two major HIV-1 coreceptors, CCR5 and CXCR4, in human peripheral blood mononuclear cells, increasing CXCR4 and decreasing CCR5 expression in primary CD4(+) T-lymphocytes. In addition, IL-4 stimulates the expression of all HIV-1 isolates via a transcriptional activation mechanism. The combination of these effects results in increased propagation of CXCR4-using and inhibition of CCR5-using HIV-1 strains. IL-4 also activates HIV-1 expression in primary monocytes/macrophages but does not affect CCR5 expression. These results identify IL-4 as an important regulator of HIV-1 and suggest a critical role for this cytokine in the control of viral evolution and in the phenotypic switch from non-syncytia-inducing to syncytia-inducing, which leads to accelerated disease progression.

Norepinephrine Accelerates HIV Replication Via Protein Kinase A-Dependent Effects on Cytokine Production

To explore the role of sympathetic nervous system activation in HIV pathogenesis, we examined the effect of the neuroeffector molecule norepinephrine (NE) on HIV-1 replication in quiescently infected PBMCs that were subsequently activated with Abs to CD3 and CD28. NE accelerated HIV-1 replication at concentrations ranging from 10−8 to 10−5 M. This effect could be mimicked by protein kinase A (PKA) activators (forskolin or dibutyryl-cAMP) and abrogated by β-adrenoreceptor antagonists or the PKA inhibitor rp-cAMP, indicating transduction via the adrenoreceptor signaling pathway. NE reduced cellular activation and altered the production of several HIV-modulating cytokines: IL-10 and IFN-γ were markedly suppressed; TNF-α, IL-1β, IL-2, IL-4, and IL-6 were mildly suppressed; and levels of IL-12 were not significantly altered. The addition of either exogenous IFN-γ or IL-10 abrogated the effect of NE on virus production. Thus PKA-dependent suppression of cytokine production appears to mediate the enhancement of HIV-1 replication by NE.

Cytokines and chemokines in HIV infection: implications for therapy

HIV infection is associated with both a hyperactivity of the immune system and decreased immune responses against specific antigens. A similar pattern is observed when considering cytokine production in HIV-infected patients. Several cytokines are spontaneously produced at an increased level, whereas other cytokines playing an important role during cell-mediated immune responses are produced at a low level following stimulation. This deregulation of cytokine production may participate to the immune deficiency, both by impairing immune responses and by accelerating CD4+ T lymphocyte destruction. Chemokine receptors have recently been shown to function as coreceptors for the virus, and to govern its cellular tropism. Heterogeneous expression of chemokine receptor may contribute to differences in infectability as well as in rate of progression of the disease between individuals. Better understanding of the role of cytokines and chemokines in HIV infection suggests new therapeutic approaches where administration of cytokines or cytokine antagonists may allow the immune system to function in better conditions, to stimulate antiviral and antiinfectious immune defenses, and to limit viral spread.

Induction of HIV-1 replication in latently infected CD4+ T cells using a combination of cytokines

Although it has been demonstrated that certain cytokines, particularly proinflammatory cytokines, can enhance ongoing viral replication in peripheral blood mononuclear cells (PBMCs) of HIV-1-infected individuals, it is unclear what role these cytokines play in the induction of HIV-1 replication in latently infected, resting CD4(+) T cells. This study demonstrates that the in vitro combination of the proinflammatory cytokines interleukin (IL)-6 and tumor necrosis factor (TNF)-alpha together with the immunoregulatory cytokine IL-2 are potent inducers of viral replication in highly purified, latently infected, resting CD4+ T cells derived from HIV-infected individuals who are antiretroviral therapy-naive as well as those who are receiving highly active antiretroviral therapy (HAART). Viral replication induced by this combination of cytokines was completely suppressed in the presence of HAART in vitro. Given that an array of cytokines, including IL-6, TNF-alpha, and IL-2, are copiously expressed in the microenvironment of the lymphoid tissues, which harbor the latent viral reservoirs, induction of HIV by this combination of cytokines may in part explain the commonly observed reappearance of detectable plasma viremia in HIV-infected individuals in whom HAART was discontinued. Moreover, since it is likely that these infected cells die upon activation of virus and that HAART prevents spread of virus to adjacent cells, the observation that this combination of cytokines can markedly induce viral replication in this reservoir may have important implications for the activation-mediated diminution of the latent reservoir of HIV in patients receiving HAART.

Infection of T cell subsets by HIV-1 and the effects of interleukin-12

CD4+ lymphocytes constitute one of the major cell targets for human immunodeficiency virus type 1 (HIV-1) infection. The eventual loss of CD4+ lymphocytes contributes substantially to the pathogenesis of HIV-1 and development of acquired immunodeficiency syndrome (AIDS). CD4+ lymphocytes consist of the subgroups Th1, Th2, and Th0, which differ in their cytokine profile. Th1 cells produce cytokines that favor cell-mediated immune responses, whereas Th2 cells produce cytokines that favor humoral immunity. Th0 cells are precursors to the Th1 and Th2 subsets. A shift from a Th1 to a Th2 response has been reported for HIV-1-infected patients (Kannagi et al. 1990. J. Virol. 64, 3399-3406; Walker et al. 1986. Science 234, 1563-1566; Walker et al. 1991. J. Virol. 65, 5921-5927). For this reason, the potential role of cytokines in the development of AIDS has received a great deal of attention. Interleukin (IL)-12 is a disulfide-linked, 70-kDa heterodimeric cytokine produced by antigen-presenting cells. IL-12 has a central role in the development of the Th1-type immune responses. Therefore, we investigated the ability of T-tropic HIV-1 IIIB to replicate in Th1, Th2, and Th0 T cell clones and studied the effects of IL-12 on HIV-1 replication in these cells types. These studies demonstrate several points. (1) Th1, Th2, and Th0 T cell clones support HIV-1 IIIB replication nearly equally well, and it is, therefore, unlikely that differences in ability to support HIV-1 replication can explain changes in Th1, Th2, or Th0 subtype 1 following HIV-1 infection. (2) Using this model, we show that IL-12 can inhibit HIV-1 replication, consistent with a role for IL-12 in HIV-1 replication in T cells. (3) HIV-1 can form a persistent infection in T cell clones, providing a reservoir model for study of viral sanctuary and persistence in a system closely approximating the in vivo situation.

Interferon-γ Increases Expression of Chemokine Receptors CCR1, CCR3, and CCR5, But Not CXCR4 in Monocytoid U937 Cells

Chemokine receptors (CR), which can mediate migration of immune cells to the site of inflammation, also function as coreceptors for human immunodeficiency virus (HIV) entry into CD4+ T lymphocytes and antigen-presenting cells. We demonstrate here that interferon-γ (IFN-γ) increases the expression of chemokine receptors CCR1, CCR3, and CCR5 in monocytoid U937 cells as detected by cell surface molecule labeling and mRNA expression, as well as by intracellular calcium mobilization and cell migration in response to specific ligands. The increased expression of these chemokine receptors also results in an enhanced HIV-1 entry into cells. Our data provide evidence for a relationship of cellular pathways that are induced by IFN-γ with those that regulate chemokine receptor expression.

Interferon-γ Increases Expression of Chemokine Receptors CCR1, CCR3, and CCR5, But Not CXCR4 in Monocytoid U937 Cells

Chemokine receptors (CR), which can mediate migration of immune cells to the site of inflammation, also function as coreceptors for human immunodeficiency virus (HIV) entry into CD4+ T lymphocytes and antigen-presenting cells. We demonstrate here that interferon-γ (IFN-γ) increases the expression of chemokine receptors CCR1, CCR3, and CCR5 in monocytoid U937 cells as detected by cell surface molecule labeling and mRNA expression, as well as by intracellular calcium mobilization and cell migration in response to specific ligands. The increased expression of these chemokine receptors also results in an enhanced HIV-1 entry into cells. Our data provide evidence for a relationship of cellular pathways that are induced by IFN-γ with those that regulate chemokine receptor expression.

Administration of interleukin 13 to simian immunodeficiency virus-infected macaques: induction of intestinal epithelial atrophy

Increase Th2 cytokine production may contribute to some clinical manifestations of HIV infection, and studies have suggested that IL-13 rather than IL-4 is involved in these conditions. We directly tested this hypothesis by administrating IL-13 to SIV-infected macaques. SIV-infected rhesus macaques received a daily subcutaneous injection for 21 days of either IL-13 (10 microg/kg/day) or a placebo. The four macaques treated with IL-13 experienced body weight loss (9.95 +/- 0.71%) related to intestinal tract damage: they all suffered from a complete atrophy of duodenal villi. This was presumably due to premature epithelial cell death: proliferating Ki67+ cells in glandular crypts were as numerous as in control animals, but many epithelial cells developed apoptosis. The duodenal mucosa was infiltrated with cells expressing CD56 and PEN5, two markers of NK cells, and there was a deregulation of local cytokine and chemokine production characterized by a decrease in IL-10 gene expression (25% of controls) and an increase in gene expression for IFN-gamma (4-fold control), MIP-1alpha (8-fold control), and MIP-1beta (13-fold control). Thus, IL-13 can induce digestive epithelial cell injury in vivo in primates infected with a retrovirus. Therefore, its role should be considered in digestive manifestations of HIV infection as well as in other disorders associated with intestinal epithelial atrophy.

Similar levels of human immunodeficiency virus type 1 replication in human TH1 and TH2 clones

Studies on the development and function of CD4+ TH1 and TH2 cells during the progression to AIDS may increase the understanding of AIDS pathogenesis. The preferential replication of human immunodeficiency virus (HIV) in either TH1 or TH2 cells could alter the delicate balance of the immune response. TH1 (gamma interferon [IFN-gamma] positive, interleukin-4 [IL-4] and IL-5 negative) and TH2 (IFN-gamma negative, IL-4 and IL-5 positive) clones, developed from several healthy donors, pedigreed by reverse transcriptase PCR (RT-PCR) and enzyme linked immunosorbent assay have similar levels of cell surface expression of CD4 and several chemokine receptor cofactors necessary for viral entry. After activation by specific antigens and infection with T-cell-tropic strains of HIV type 1 (HIV-1), TH1 and TH2 clones showed similar levels of viral entry and reverse transcription. At days 3 through 14 postinfection, HIV replicated to similar levels in several TH1 and TH2 clones as measured by release of HIV p24 and total number of copies of gag RNA/total cell RNA as measured by RT-PCR. When values were normalized for viable cell number in three clones of each type, there was up to twofold more HIV RNA in TH1 than TH2 cells. In addition, several primary monocytotropic HIV-1 strains were able to replicate to similar levels in TH1 and TH2 cells. These studies suggest that the importance of TH1 and TH2 subsets in AIDS pathogenesis transcends clonal differences in their ability to support HIV replication.

Accelerated changes (inflection points) in levels of serum immune activation markers and CD4+ and CD8+ T cells prior to AIDS onset

The trajectories of change in CD4+ and CD8+ lymphocytes and serum neopterin and beta2-microglobulin (beta2M) levels were determined in 158 HIV-seropositive individuals during 5.5 years before a clinical AIDS diagnosis. Each patient was evaluated separately using a two-piece regression model with seven possible change points to identify any adverse change (inflection point) in the slopes of each immunologic marker of HIV infection. Two categories of subjects were distinguished for each marker--those with statistically significant inflection points and those who demonstrated a steady progression of changes to AIDS. Fifty-nine percent had an inflection point for CD4+ T cells. The frequency of inflection points for CD8+ was 49%, for serum neopterin -48% and for beta2M -38%. Inflection points were found over a 4-year span. Three distinctive categories of inflection points were observed on the basis of their independent occurrence: one was in CD4+ T cells, another in CD8+ T cells, and a third in the serum markers of immune activation. The inflection point for CD4+ usually occurred prior to those for CD8+ T cells (p=.0002). The HIV-positive persons with inflection points were diagnosed with AIDS when immunologic parameters were significantly more abnormal than in those with steady progression (p < .0003). Thus, these two groups differed in the course of immune changes and in the levels of immune abnormalities associated with the occurrence of clinical AIDS.

CD4+ and CD8+ T Cell Interactions in IFN-γ and IL-4 Responses to Viral Infections: Requirements for IL-2

Cytokine responses to lymphocytic choriomeningitis virus infections were evaluated, and CD8+ T cell, CD4+ T cell, and IL-2 contributions delineated. In immunocompetent mice, lymphocytic choriomeningitis virus induced both IFN-γ and IL-4 as well as IL-2. Experiments in mice either β2-microglobulin-deficient, lacking MHC class I molecules and CD8+ T cells, or Aβb-deficient, lacking MHC class II molecules and CD4+ T cells, demonstrated that mixtures of T cell responses were required for optimal ex vivo cytokine productions. Intracellular cytokine expression analyses of cells from immunocompetent and immunodeficient mice showed that CD8+ T cells were predominant IFN-γ producers, and that expansion of CD8+ T cells primed to make IFN-γ was independent of CD4+ T cells in vivo. Studies in IL-2-deficient mice demonstrated that this cytokine promoted IFN-γ and IL-4 responses, and ex vivo experiments showed that exogenous IL-2 was required to maintain high-level IFN-γ production by in vivo-primed CD8+ T cells. Conditions associated with cytokine decreases were accompanied by reduced detectable plasma Ab responses. The results indicate that, although IL-2-dependent CD8+ T cell proliferation does not require endogenous CD4+ T cells, IL-2 production by the CD4+ T cells may promote continued cytokine release from activated CD8+ T cells. By defining these critical steps in cellular and cytokine interactions for shaping endogenous immune responses, the studies advance understanding of the unique conditions regulating CD8+ T cell responses to viral challenges.

Single-cell analysis of lymphokine imbalance in asymptomatic HIV-1 infection: evidence for a major alteration within the CD8+ T cell subset

In this study we investigated at single-cell level by flow cytometry the potential of T cell cytokine production in asymptomatic HIV-1-infected subjects with > 200 CD4 counts and possible correlation with T helper cell depletion and viral load. Mitogen-stimulated peripheral blood mononuclear cells from 32 HIV-1+ patients and 16 healthy subjects were intracytoplasmically stained for IL-2, interferon-gamma (IFN-gamma), IL-4 or IL-10, and the frequency of cytokine-producing cells was assessed in total T cells, CD4, CD8 and CD45RO subsets as well as in CD69+CD3+ gated lymphocytes. HIV-1+ patients, irrespective of their degree of CD4 depletion, exhibited a major increase in IFN-gamma+ CD8 T cells, largely due to CD28- cells, as well as a decrease in the capacity of CD8 T cells to produce IL-2. Patients with > 500 CD4 counts showed a diminished frequency of IL-4 expression in CD4 T cells and a negative correlation was found between this parameter and the ex vivo CD4 counts in the 32 patients. Analysis of patients stratified according to viral load revealed a significantly higher proportion of IL-2-producing CD4 cells in the group with < 5000 RNA copies/ml. In short, using single-cell analysis and an antigen-presenting cell-independent stimulus, we have not been able to find any significant cytokine imbalances in the CD4 subset, suggesting that the well described T helper defects are not due to intrinsic alterations in the potential of CD4 T cells to produce cytokines. On the other hand, the major disturbances in the CD8 T lymphocytes agree with the marked activation and possible replicative senescence of CD8 T cells and emphasize the role of this subset in HIV immunopathogenesis.

HIV-1 does not alter in vitro and in vivo IL-10 production by human monocytes and macrophages

The present study analyses the ability of HIV-1 to modulate IL-10 production in cells of monocyte-macrophage lineage cultured in the presence of macrophage colony-stimulating factor (M-CSF). Both monocytes and macrophages spontaneously produced low amount of IL-10. Lipopolysaccharide (LPS) induced a strong IL-10 response in fresh monocytes and in M-CSF-treated macrophages. In contrast, macrophages cultured in the absence of M-CSF exhibited a marked decrease in their susceptibility to LPS stimulation. M-CSF increased the IL-10 response of macrophages to LPS by enhancing both the expression of membrane-bound CD14, the protein that serves as LPS receptor, and the sensibility of CD14-expressing cells to LPS stimulation. Neither spontaneous nor LPS-induced expression of IL-10 was modulated in monocytes and macrophages by infection with eight monocytotropic strains, as demonstrated by ELISA and cytofluorimetric analysis. In contrast, all the HIV-1 strains primed macrophages for an increased IL-6 response to LPS stimulation. To determine whether IL-10 production was associated with in vivo infection, monocytes from AIDS individuals were analysed for IL-10 production. We found that neither spontaneous nor LPS-induced IL-10 production were different between healthy controls and HIV-infected patients. Taken together, these data strongly suggest that HIV-1 infection of monocytes-macrophages does not play a significant role in the regulation of IL-10 in infected patients. This study also emphasizes the role of M-CSF activation in the regulation of the cytokine response in macrophages.

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.

Expression of macrophage inflammatory protein (MIP)-1alpha, MIP-1beta, and RANTES genes in lymph nodes from HIV+ individuals: correlation with a Th1-type cytokine response

The in vivo response of the immune system after HIV infection in regard to cytokine production and C-C chemokine synthesis is not well known. Here we have analysed cytokine and chemokine mRNA production in lymph nodes with follicular hyperplasia (FHLN) of HIV-infected patients by in situ hybridization using anti-sense mRNA probes. The synthesis of mRNAs for interferon-gamma (IFN-gamma), IL-12p35, IL-12p40, IL-4, and for the C-C chemokines RANTES, MIP-1alpha, and MIP-1beta was compared with that of lymph nodes from non-infected individuals to define HIV-specific events. Only few cells expressing IFN-gamma, RANTES, MIP-1alpha, and MIP-1beta mRNAs were detectable in the T-dependent area of lymph nodes from HIV-negatives. In contrast, in FHLN from HIV+ patients a high number of IFN-gamma, RANTES, MIP-1alpha, and MIP-1beta mRNA-containing cells were detectable. Remarkably, only single individual IL-12p35 mRNA-producing cells were present in the T-dependent area from both HIV+ and HIV lymph nodes. Furthermore, the low number of IL-12p40 mRNA-expressing cells did not differ between HIV+ and HIV- lymph nodes. This indicates that IFN-gamma is expressed independently of IL-12, possibly by a direct T cell-mediated reaction. IL-4 mRNA-producing cells were hardly detectable in infected and control lymph nodes. The same findings were made in a limited number of samples from patients with advanced disease. Thus, these results demonstrate that a high IFN-gamma production is accompanied by a strong expression of MIP-1alpha, MIP-1beta, and RANTES in the lymph node after HIV infection. This favours the idea that a Th1-type immune response correlates with a preferential production of C-C chemokines in FHLN of HIV+ patients.

Intracellular cytokine expression in the CD4+ and CD8+ T cells from intestinal mucosa of simian immunodeficiency virus infected macaques

Isolated intraepithelial lymphocytes (IEL) and lamina propria lymphocytes (LPL) from jejunum of SIV infected animals were examined for alterations in basal cytokine expression by RT-PCR. Remarkable changes in IFNgamma and IL-10 RNA levels were observed in IEL and LPL in SIV infection while IL-4 and IL-2 RNA levels remained unaltered. In addition, the CD4+ and CD8+ LPL were examined for intracellular cytokine production following mitogenic activation by flowcytometry. Both CD4+ and CD8+ T lymphocytes in intestinal mucosa retained the potential to produce IFNgamma in response to mitogenic stimulation in vitro, without a remarkable change in IL-4 production. The dominant IFNgamma cytokine response could be one of the major contributing factors in SIV associated enteropathy.

Phenotypic variability of lymphocyte populations in peripheral blood and lymph nodes from HIV-infected individuals and the impact of antiretroviral therapy. DATRI 003 Study Group. Division of AIDS Treatment Research Initiative

This study presents immunophenotypic variation in lymphocyte populations obtained from peripheral blood and lymph nodes from individuals with early HIV disease who were enrolled in a prospective, open-label study. At baseline, there was a significantly greater percentage of B cells and significantly smaller percentage of CD8+ cells in lymph nodes compared with peripheral blood. Evaluation of lymphocyte phenotypic markers of function, maturation, and activation at baseline revealed a significantly higher percentage of activated CD4+ cells in lymph nodes compared with peripheral blood, whereas the percentages of activated CD8+ cells were similar in both compartments. After an 8-week period of randomly assigned treatment, peripheral blood phenotypic marker changes included (1) a reduced proportion of activated cells (HLA-DR+) in antiretroviral-naive patients who received zidovudine (ZDV), and (2) as increased proportion of "naive" cells (CD45RA+) in individuals, previously administered ZDV alone, who received ZDV and didanosine (ddI) therapy. The lymph node phenotypic marker analysis showed no significant changes over the 8-week treatment period. Overall, the study demonstrates significant differences in lymphocyte subsets from lymph nodes compared with peripheral blood and suggests that further studies be performed to determine the functional significance of these phenotypic subsets.

Ultra low dose interleukin-2 therapy promotes a type 1 cytokine profile in vivo in patients with AIDS and AIDS-associated malignancies

This study was undertaken to determine if prolonged daily subcutaneous administration of ultra low dose IL-2 could influence the constitutive endogenous production of a type 1 (IFN-gamma) cytokine in patients with AIDS or AIDS-associated malignancies. Using a quantitative reverse transcription PCR assay, we demonstrate that daily administration of one type 1 cytokine, IL-2, for 3 mo increases significantly the constitutive endogenous gene expression of another type 1 cytokine, IFN-gamma, in vivo. The predominant source of IFN-gamma appears to be IL-2-expanded natural killer cells and CD8(+) T cells. Moreover, PBMC obtained from these patients during IL-2 therapy showed normalization of a profound deficit in IFN-gamma protein production after stimulation with extracts from infectious agents in vitro. Our data suggest that prolonged exogenous administration of a type 1 cytokine in a nontoxic fashion to patients with AIDS and AIDS-associated malignancies can enhance significantly the endogenous type 1 cytokine profile in vivo. Consequently, ultra low dose IL-2 therapy has the potential to improve the immunodeficient hosts' immune response to infectious pathogens that require IFN-gamma for clearance.

Altered receptor expression and decreased sensitivity of T-cells to the stimulatory cytokines IL-2, IL-7 and IL-12 in HIV infection

A dysregulated production of regulatory cytokines has been proposed as a determinant in the progression of HIV infection. The sensitivity of T-cells to these cytokines has, however, not fully been investigated. Therefore, the responses of PBMC and T-cell subsets to the stimulatory cytokines IL-2, IL-7 and IL-12 in HIV-infected patients and HIV-negative controls were compared by examining their effect on the production of secondary cytokines (IFNgamma, IL-4 and IL-10), by simultaneous determination of T-cell activation and apoptosis and by measuring cytokine receptor expression. Production of IFNgamma was decreased in PBMC from the patients after stimulation with several combinations of stimulatory cytokines. IL-10 was only induced upon stimulation with IL-2 and IL-12 and tended to be produced more in patients. Expression of the different cytokine receptor chains showed complex alterations in HIV+ patients as compared to controls. The most pronounced changes were decreased expression of both IL-2Ralpha and IL-7Ralpha chain on CD8+ T-cells and an increase of IL-12Rbeta on both T-cell subsets from the patients. Evaluation of CD25 upregulation and blast formation revealed a deficient response to all three stimulatory cytokines in CD8+ but not in CD4+ T-cells from patients as compared to controls. Both CD4+ and CD8+ T-cells from the patients were less sensitive to the anti-apoptotic effect of IL-7 whereas only CD8+ T-cells were less sensitive to the anti-apoptotic effect of IL-2. The present data show that CD8+ T-cells, and to a lesser extent CD4+ T-cells, become less sensitive to IL-2, IL-7 and IL-12 during HIV infection. The decreased capacity of T-cells to respond to these cytokines could contribute to the HIV-related immune dysfunction.

In vivo alteration in type-1 and type-2 cytokine balance: a possible mechanism for elevated total IgE in HIV-infected patients

The progression of HIV infection has been associated with an increase in the plasma levels of total IgE. The mechanisms responsible for the increased IgE have not been elucidated. The type-1 and type-2 cytokine imbalance associated with HIV infection has been proposed as a possible mechanism for elevated IgE. The current study was undertaken to investigate the relationship between total IgE, type-1 and type-2 cytokines from a large HIV+ patient population. HIV+ patients were found to have elevated total IgE that inversely correlated with numbers of CD4+ T-cells. HIV+ plasma was also found to have decreased IFN-gamma and IL-12p70 levels as well as increased IL-10 levels compared to HIV-negative individuals. HIV+ patients with more advanced disease, as defined by absolute CD4+ counts, demonstrated more marked differences. Furthermore, the relative ratios of IFN-gamma:IL-10 and IL-12:IL-10 were decreased in HIV+ patients compared to HIV-negative individuals. The alterations in the plasma cytokines suggest a switch from a predominance of type-1 cytokines to type-2 cytokines that may enhance IgE synthesis. These data suggest that measurement of plasma IgE and/or cytokines may have prognostic or therapeutic monitoring value in HIV+ patients.

CD40 ligand and IFN-gamma synergistically restore IL-12 production in HIV-infected patients

IL-12 production in HIV-infected (HIV+) individuals is severely impaired after stimulation by bacterial products or T cell-dependent stimuli. Because CD40-CD40 ligand (CD40L) interactions are the major mechanism involved in the T cell-dependent activation of antigen-presenting cells, we investigated whether this pathway was functional in HIV+ donors. CD40 expression was increased on freshly isolated monocytes from HIV+ individuals compared to HIV donors. However, equivalent CD40 expression was obtained in the two groups after cytokine stimulation. Since CD40 expression was intact in HIV+ donors' cells, we determined whether IL-12 production could be restored by providing exogenous T cell-dependent stimuli, CD40L and IFN-gamma, at the time of bacterial stimulation. IL-12 production was not altered by CD40L alone, was increased by IFN-gamma, and was synergistically restored to normal values by IFN-gamma + CD40L. This combination was more efficient for enhancing IL-12 production than granulocyte-macrophage colony-stimulating factor + CD40L or neutralizing anti-IL-10 antibody + CD40L. CD40L did not affect IL-10 production, whereas IFN-gamma significantly decreased it. This study demonstrates that the defect in IL-12 production by leukocytes from HIV+ donors can be overcome in vitro if the interacting cells are provided with the right T cell-dependent co-stimuli.

Lack of polarized type 1 or type 2 cytokine profile in asymptomatic HIV-1-infected patients during a two-year bimonthly follow-up

The production of type 1 (interferon or IFN-gamma) and type 2 (interleukin or IL-4 and IL-10) cytokines by mitogen-stimulated peripheral blood mononuclear cells (PBMCs) obtained from asymptomatic human immunodeficiency virus-seropositive (HIV+) patients untreated with any antiviral, antibacterial or antimycotic drugs, and from healthy individuals, was evaluated by quantitative ELISA. Patients who were HIV+ were characterized by the absence of abnormal cytokine production. The level of each cytokine differed among individuals in the same group with intersubject variations greater for HIV+ patients than for healthy individuals. The longitudinal evaluation of IFN-gamma, IL-4 and IL-10 production showed intrasubject variations which were particularly marked in HIV+ patients. Accordingly, HIV+ patients and, to a lesser extent, healthy individuals were characterized by a wide spectrum of possible profiles, which were confined to type 0 phenotype. In HIV+ patients no correlation was found between each cytokine level and the number of CD4+ T cells, not even in those with a falling CD4+ T-cell count and clinical symptoms.

IL-10 prevents the differentiation of monocytes to dendritic cells but promotes their maturation to macrophages

Human monocytes cultured with granulocyte-macrophage colony-stimulating factor (GM-CSF) and IL-13 for 7 days differentiate into cells with the morphology and function of dendritic cells (DC). We have investigated the effect of IL-10 on this differentiation pathway. In the presence of IL-10 cells did not develop DC morphology, did not express CD1a and had lower levels of MHC class II. IL-10 promoted the differentiation of large cells with the morphology, cytochemistry and membrane phenotype of macrophages, including staining for nonspecific esterase and high levels of CD14, CD16 and CD68. The effect of IL-10 was dose dependent and was best appreciated when the cytokine was added at the initiation of the culture, as addition on day 3 was less inhibitory. When added to already differentiated DC on day 6, IL-10 caused only a modest reduction of MHC class II and CD1a expression, and no acquisition of the macrophage markers CD14, CD16 and CD68. Prolonged incubation up to 5 days with IL-10 did not induce a shift of differentiated DC to macrophages. On the other hand, the macrophages obtained by culturing for 7 days with GM-CSF+IL-13+IL-10 did not shift to DC upon removal of IL-10 for up to 3 days. Thus, the effect of IL-10 on monocyte differentiation, occurs only at the precursor level and confers an irreversible phenotype. From a functional point of view, cells cultured in the presence of IL-10 were poor stimulators of allogeneic cord blood T cells in mixed lymphocyte reaction (MLR) and presented tetanus toxin (TT) to specific T cell lines with much less efficiency than control DC. In contrast, IL-10-cultured DC showed 7 times greater endocytosis of FITC-dextran. This increased endocytosis was mostly mediated via the mannose receptor, as demonstrated by blocking with unlabeled mannose. In conclusion, IL-10 inhibits DC differentiation from monocytes and, in a substantial proportion of the cells, promotes the differentiation to mature macrophages. Intriguingly, IL-10 inhibits antigen presentation while it stimulates endocytic activity.

HIV-induced IL-6/IL-10 dysregulation of CD4 cells is associated with defective B cell help and autoantibody formation against CD4 cells

To analyse CD4 cell cytokine secretion and helper/suppressor function at a clonal level we established 446 CD4+ T cell clones (TCC) in four healthy controls, three HIV- haemophilia patients, four CDC II,III and four CDC IV patients. Spontaneous TCC secretion of Th1 cytokines (IL-2, interferon-gamma (IFN-gamma)) and Th2 cytokines (IL-4, IL-6, IL-10) was determined by ELISA. TCC helper and suppressor functions were tested in a pokeweed mitogen (PWM)-stimulated allogeneic co-culture system using a reverse haemolytic plaque assay for assessment of B cell responses. There was a significant association of TCC surface marker expression (Leu-8, CD45RA) with TCC IL-6 secretion in healthy controls (P < 0.01), HIV- patients (P < or = 0.001) and CDC II,III patients (P < or = 0.01) but not in CDC IV patients. Likewise, TCC expression of Leu-8 and CD45RA was significantly associated with TCC suppressor function in healthy controls (P < or = 0.0005) but not in HIV-infected patients. A reduced TCC helper frequency (< or = 10% of TCC) and an enhanced TCC suppressor frequency (> 80% of TCC) were detected only in those HIV-infected patients who showed an excessively increased TCC IL-6 secretion (> 70% of TCC) together with a significantly diminished TCC IL-10 secretion (< or = 10% of TCC). CD4 cell autoantibodies also were found only in patients with this type of cytokine dysregulation. These data indicate that CD4 cell surface markers lose their functional relevance in HIV-infected patients. HIV-induced IL-6/IL-10 dysregulation of CD4+ T cells, i.e. the up-regulation of spontaneous IL-6 and down-regulation of spontaneous IL-10 secretion, appears to be involved in inducing CD4 helper defects and may promote autoantibody formation against CD4 cells.