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author:("loossi, Zahra")
1.  Short Communication: Circulating Plasma HIV-1 Viral Protein R in Dual HIV-1/Tuberculosis Infection 
Circulating free HIV-1 viral protein R (Vpr) is found in up to one third of subjects with HIV-1 infection. Free Vpr presumably shares some of the immunopathogenic effects of cell-associated Vpr. Here we assessed Vpr in plasma and pleural fluid from HIV/tuberculosis (TB) dually infected subjects with pleural TB and from plasma of patients with pulmonary HIV/TB. Vpr was assessed by western blot analysis. In plasma from HIV/TB subjects with pulmonary TB free Vpr could be detected in 47%. Only one subject, among 26 tested, with HIV monoinfection showed plasma Vpr activity. The majority (87.5%) of patients with pleural HIV/TB demonstrated free Vpr reactivity in their plasma. However, no Vpr activity was found in autologous pleural fluid samples from pleural HIV/TB patients. Standard (s) Vpr reactivity was reduced markedly by the addition of sVpr to pleural fluid from HIV-uninfected subjects. A high incidence of plasma Vpr reactivity in HIV/TB patients implies heightened processing and release of this HIV-1 accessory protein during HIV/TB coinfection. The contribution of free Vpr to HIV-1 immunopathogenesis during HIV/TB needs to be studied.
PMCID: PMC4076988  PMID: 24798102
2.  Role of protease inhibitor 9 in survival and replication of Mycobacterium tuberculosis in mononuclear phagocytes from HIV-1-infected patients 
AIDS (London, England)  2014;28(5):679-687.
Objective and design
Predisposition to opportunistic infections by Mycobacterium tuberculosis (MTB) is a concomitant of HIV-1 infection and occurrence of tuberculosis is independent of circulating CD4+ T-cell count in HIV-1-infected patients. Infection of mononuclear phagocytes from healthy individuals by virulent MTB is associated with expression of the antiapoptotic molecule protease inhibitor 9 (PI-9), and PI-9 contributes to successful parasitism of macrophages by MTB. Here we studied the contribution of PI-9 to successful MTB infection of monocytes from HIV-1-infected patients.
Blood monocytes obtained from HAART-treated HIV-1-infected patients (HIV+) and healthy controls were assessed for support of MTB H37Rv growth by assessment of MTB 16S ribosomal (r)RNA in cell lysates on day 1 and day 7 by real-time reverse transcription-PCR. PI-9 expression in monocyte cell lysates was assessed by ELISA and by reverse transcription-PCR. Inhibition of intracellular PI-9 was achieved by siRNA to PI-9 and compared to control constructs.
Monocytes from HIV-infected patients supported higher MTB growth [MTB 16S rRNA (d7/d1)] as compared with monocytes from healthy controls. Both PI-9 protein and mRNA were significantly higher in monocytes from HIV-infected patients as compared with healthy controls. PI-9 protein levels prior to MTB infection correlated with MTB replication on day 7, and with plasma soluble CD14 levels. Silencing of PI-9 by transfection of monocytes from HIV-1-infected patients with PI-9-specific siRNA prior to infection improved intracellular containment of MTB.
Increased intracellular PI-9 activity in mononuclear phagocytes from HIV-infected patients contributes to successful intracellular infection by virulent MTB.
PMCID: PMC4454385  PMID: 24445365
HIV-1 infection; monocyte; Mycobacterium tuberculosis; protease inhibitor 9
3.  Systemic Immune Activation and Microbial Translocation in Dual HIV/Tuberculosis-Infected Subjects 
The Journal of Infectious Diseases  2013;207(12):1841-1849.
Background. Systemic immune activation is a strong predictor of progression of human immunodeficiency virus type 1 (HIV-1) disease and a prominent feature of infection with Mycobacterium tuberculosis.
Objective. To understand the role of systemic immune activation and microbial translocation in HIV/tuberculosis dually infected patients over the full spectrum of HIV-1 immunodeficiency, we studied circulating sCD14 and lipopolysaccharide (LPS) and their relationship to HIV-1 activity.
Methods. Two cohorts of HIV/tuberculosis subjects defined by CD4 T-cell count at time of diagnosis of tuberculosis were studied: those with low (<350/μL) and those with high (≥350/μL) CD4 T-cell count. Circulating soluble CD14 (sCD14) and LPS were assessed.
Results. Levels of sCD14 were higher in HIV/tuberculosis with high (≥350/μL) as compared to low CD4 T-cell count (P < .001). Whereas sCD14 levels remained elevated in HIV/tuberculosis subjects with lower CD4 T-cell counts despite treatment of tuberculosis, in HIV/tuberculosis patients with higher CD4 T-cell count (≥350/μL), levels declined regardless of whether highly active antiretroviral therapy (HAART) was included with the anti-tuberculosis regimen. Circulating LPS levels in HIV/tuberculosis patients with CD4 T-cell count ≥350/μL were unaffected by treatment of tuberculosis with or without HAART.
Conclusion. During HIV/tuberculosis, systemic immune activation is dissociated from microbial translocation. Changes in circulating sCD14 and LPS are dependent on CD4 T-cell count.
PMCID: PMC3654743  PMID: 23479321
HIV-1; tuberculosis; LPS; soluble CD14
4.  Effect of Nadir CD4+ T Cell Count on Clinical Measures of Periodontal Disease in HIV+ Adults before and during Immune Reconstitution on HAART  
PLoS ONE  2013;8(10):e76986.
The contribution of HIV-infection to periodontal disease (PD) is poorly understood.  We proposed that immunological markers would be associated with improved clinical measures of PD.
We performed a longitudinal cohort study of HIV-infected adults who had started highly active antiretroviral therapy (HAART) <2 years. PD was characterized clinically as the percent of teeth with ≥1 site with periodontal probing depth (PPD) ≥5.0mm, recession (REC) >0mm, clinical attachment level (CAL) ≥4.0mm, and bleeding on probing (BOP) at ≥4 sites/tooth and microbiologically as specific periodontopathogen concentration. Linear mixed-effects models were used to assess the associations between immune function and PD.
Forty (40) subjects with median 2.7 months on HAART and median nadir CD4+ T-cell count of 212 cells/μl completed a median 3 visits. Over 24 months, CD4+ T-cell count increased by a mean 173 cells/µl (p<0.001) and HIV RNA decreased by 0.5 log10 copies/ml (p<0.001); concurrently, PPD, CAL and BOP decreased by a mean 11.7%, 12.1%, and 14.7% respectively (all p<0.001). Lower nadir CD4+ T-cell count was associated with worse baseline REC (-6.72%; p=0.04) and CAL (9.06%; p<0.001). Further, lower nadir CD4+ T-cell count was associated with a greater relative longitudinal improvement in PPD in subjects with higher baseline levels of Porphyromonas gingivalis (p=0.027), and BOP in subjects with higher baseline levels of Porphyromonas gingivalis or Treponema denticola (p=0.001 and p=0.006 respectively). Longitudinal changes from baseline in CD4+ T-cell count and level of HIV RNA were not independently associated with longitudinal changes in any clinical markers of PD.
Degree of immunosuppression was associated with baseline gingival recession. After HAART initiation, measures of active PD improved most in those with lower nadir CD4+ T-cell counts and higher baseline levels of specific periodontopathogens. Nadir CD4+ T-cell count differentially influences periodontal disease both before and after HAART in HIV-infected adults.
PMCID: PMC3795634  PMID: 24146949
5.  Inhibition of M. tuberculosis induced signaling by transforming growth factor-β in human mononuclear phagocytes 
Tuberculosis (TB) is associated with excessive production and bio-activation of transforming growth factor bets (TGF-β) in situ. Here, modification of expression of components of plasminogen/plasmin pathway in human monocytes (MN) by inhibitors of TGF-β signaling were examined. Smad3 siRNA effectively inhibited TGF-β induced urokinase plasminogen activator receptor (uPAR). Agents known to interfere with TGF-β signaling, including the Smad inhibitors SIS3 and Erythromycin derivatives, and ALK5 receptor inhibitor (SB 431542) in inhibition of uPAR expression in response to MTB were examined. Inhbibition by SIS 3 only sinhibited uPAR mRNA significantly. SIS3 may prove to be an effective adjunct to TB therapy.
PMCID: PMC3279592  PMID: 22150316
6.  Activation of P-TEFb at Sites of Dual HIV/TB Infection, and Inhibition of MTB-Induced HIV Transcriptional Activation by the Inhibitor of CDK9, Indirubin-3′-Monoxime 
At sites of Mycobacterium tuberculosis (MTB) infection, HIV-1 replication is increased during tuberculosis (TB). Here we investigated the role of positive transcription elongation factor (P-TEFb), comprised of CycT1 and CDK9, as the cellular cofactor of HIV-1 Tat protein in transcriptional activation of HIV-1 in mononuclear cells from HIV-1-infected patients with pleural TB. Expression of CycT1 in response to MTB was assessed in mononuclear cells from pleural fluid (PFMC) and blood (PBMC) from HIV/TB patients with pleural TB, and in blood monocytes (MN) from singly infected HIV-1-seropositive subjects. We then examined whether the CDK9 inhibitor, Indirubin 3′-monoxime (IM), was effective in inhibition of MTB-induced HIV-1 mRNA expression. We found higher expression of CycT1 mRNA in PFMCs as compared to PBMCs from HIV/TB-coinfected subjects. MTB induced the expression of CycT1 and HIV-1 gag/pol mRNA in both PFMCs from HIV/TB subjects and MN from HIV-1-infected subjects. CycT1 protein was also induced by MTB stimulation in PFMCs from HIV/TB patients, and both MN and in vitro-derived macrophages. Inhibition of CDK9 by IM in both PFMCs from HIV/TB and MN from HIV-1-infected subjects in response to MTB led to inhibition of HIV-1 mRNA expression. These data imply that IM may be useful as an adjunctive therapy in control of HIV-1 replication in HIV/TB dually infected subjects.
PMCID: PMC3275925  PMID: 21453127
7.  Induction of Serine Protease Inhibitor 9 by Mycobacterium tuberculosis Inhibits Apoptosis and Promotes Survival of Infected Macrophages 
The Journal of Infectious Diseases  2011;205(1):144-151.
Our recent microarray analysis of infected human alveolar macrophages (AMs) found serine protease inhibitor 9 (PI-9) to be the most prominently expressed of a cluster of apoptosis-associated genes induced by virulent Mycobacterium tuberculosis. In the current study, we show that induction of PI-9 occurs within hours of infection with M. tuberculosis H37Rv and is maintained through 7 days of infection in both AMs and blood monocytes. Inhibition of PI-9 by small inhibitory RNA decreased M. tuberculosis–induced expression of the antiapoptotic molecule Bcl-2 and resulted in a corresponding increase in production of caspase 3, a terminal effector molecule of apoptosis. Further, PI-9 small inhibitory RNA mediated a significant reduction in the subsequent survival of M. tuberculosis within AMs. Thus PI-9 induction within human mononuclear phagocytes by virulent M. tuberculosis serves to protect these primary targets of infection from elimination by apoptosis and thereby promotes intracellular survival of the organism.
PMCID: PMC3242743  PMID: 22090449
8.  A Prospective Cohort Study of Periodontal Disease Measures and Cardiovascular Disease Markers in HIV-Infected Adults 
AIDS Research and Human Retroviruses  2011;27(11):1157-1166.
The determinants of HIV-associated cardiovascular disease (CVD) are not well understood. Periodontal disease (PD) has been linked to CVD but this connection has not been examined in HIV infection. We followed a cohort of HIV-infected adults to ascertain whether PD was associated with carotid artery intima media thickness (IMT) and brachial artery flow-mediated dilation (FMD). We performed a longitudinal observational study of HIV-infected adults on HAART for <2 years with no known heart disease. PD was characterized clinically and microbiologically. Cardiovascular disease was assessed by IMT/FMD. Linear mixed models assessed cross-sectional and longitudinal associations between PD and FMD/IMT. Forty three HIV+ adults completed a median of 24 (6–44) months on the study. Defining delta to be the change in a variable between baseline and a follow-up time, longitudinally, on average and after adjusting for change in time, CVD-specific and HIV-specific potential confounding covariates, a 1-log10 increase in delta Porphyromonas gingivalis was associated with a 0.013 mm increase in delta IMT (95% CI: 0.0006–0.0262; p=0.04). After adjusting for the same potential confounding covariates, a 10% increase in delta gingival recession was associated with a 2.3% increase in delta FMD (95% CI: 0.4–4.2; p=0.03). In a cohort of HIV-infected adults, an increase in subgingival Porphyromonas gingivalis, a known periodontal pathogen, was significantly associated with longitudinal increases in IMT, while increased gingival recession, which herein may represent PD resolution, was significantly associated with longitudinal improvement in FMD. In the context of HIV infection, PD may contribute to CVD risk. Intervention studies treating PD may help clarify this association.
PMCID: PMC3206743  PMID: 21443451
10.  Short Communication: Induction of HIV Type 1 Expression Correlates with T Cell Responsiveness to Mycobacteria in Patients Coinfected with HIV Type 1 and Mycobacterium tuberculosis 
An in vitro mononuclear cell system to model the microenvironment of coinfection with HIV-1 and Mycobacterium tuberculosis (MTB) was developed. This cellular system was used to assess the interaction of MTB-infected monocytes and T cells from dually infected HIV-1/TB patients with pulmonary tuberculosis (TB). Subjects with higher induction of HIV-1 gag/pol mRNA expression after MTB stimulation had increased MTB-specific T cell IFN-γ and TNF-α production. Lack of HIV-1 mRNA induction did not correlate with increased induction of regulatory T cells (T-reg) as measured by MTB-induced Foxp3 mRNA. HIV-1 induction did not significantly correlate with clinical parameters including plasma HIV-1 viral load or CD4+ T cell count. These data model MTB-induced HIV-1 replication at the microenvironment of MTB reactivation/infection. The data suggest that the magnitude of MTB-specific T cell responses drives local viral pathogenesis regardless of the stage of HIV-1 disease as reflected by plasma viral load or CD4+ T cell count.
PMCID: PMC2853903  PMID: 19239361
11.  Response to M. tuberculosis selected RD1 peptides in Ugandan HIV-infected patients with smear positive pulmonary tuberculosis: a pilot study 
Tuberculosis (TB) is the most frequent co-infection in HIV-infected individuals still presenting diagnostic difficulties particularly in developing countries. Recently an assay based on IFN-gamma response to M. tuberculosis RD1 peptides selected by computational analysis was developed whose presence is detected during active TB disease. Objective of this study was to investigate the response to selected RD1 peptides in HIV-1-infected subjects with or without active TB in a country endemic for TB and to evaluate the change of this response over time.
30 HIV-infected individuals were prospectively enrolled, 20 with active TB and 10 without. Among those with TB, 12 were followed over time. IFN-gamma response to selected RD1 peptides was evaluated by enzyme-linked immunospot (ELISPOT) assay. As control, response to RD1 proteins was included. Results were correlated with immune, microbiological and virological data.
Among patients with active TB, 2/20 were excluded from the analysis, one due to cell artifacts and the other to unresponsiveness to M. tuberculosis antigens. Among those analyzable, response to selected RD1 peptides evaluated as spot-forming cells was significantly higher in subjects with active TB compared to those without (p = 0.02). Among the 12 TB patients studied over time a significant decrease (p =< 0.007) of IFN-gamma response was found at completion of therapy when all the sputum cultures for M. tuberculosis were negative. A ratio of RD1 peptides ELISPOT counts over CD4+ T-cell counts greater than 0.21 yielded 100% sensitivity and 80% specificity for active TB. Conversely, response to RD1 intact proteins was not statistically different between subjects with or without TB at the time of recruitment; however a ratio of RD1 proteins ELISPOT counts over CD4+ T-cell counts greater than 0.22 yielded 89% sensitivity and 70% specificity for active TB.
In this pilot study the response to selected RD1 peptides is associated with TB disease in HIV-infected individuals in a high TB endemic country. This response decreases after successful therapy. The potential of the novel approach of relating ELISPOT spot-forming cell number and CD4+ T-cell count may improve the possibility of diagnosing active TB and deserves further evaluation.
PMCID: PMC2267196  PMID: 18226199
12.  Persistent Replication of Human Immunodeficiency Virus Type 1 despite Treatment of Pulmonary Tuberculosis in Dually Infected Subjects 
Tuberculosis (TB) is the most common life-threatening infection in human immunodeficiency virus (HIV)-infected persons and frequently occurs before the onset of severe immunodeficiency. Development of TB is associated with increased HIV type 1 (HIV-1) viral load, a fall in CD4 lymphocyte counts, and increased mortality. The aim of this study was to examine how treatment of pulmonary TB affected HIV-1 activity in HIV-1/TB-coinfected subjects with CD4 cell counts of >100 cells/μl. HIV-1/TB-coinfected subjects were recruited in Kampala, Uganda, and were monitored over time. Based upon a significant (0.5 log10 copies/ml) decrease in viral load by the end of treatment, two patient groups could be distinguished. Responders (n = 17) had more rapid resolution of anemia and pulmonary lesions on chest radiography during TB treatment. This group had a significant increase in viral load to levels not different from those at baseline 6 months after completion of TB treatment. HIV-1 viral load in nonresponders (n = 10) with TB treatment increased and at the 6 month follow-up was significantly higher than that at the time of diagnosis of TB. Compared to baseline levels, serum markers of macrophage activation including soluble CD14 decreased significantly by the end of TB treatment in responders but not in nonresponders. These data further define the impact of pulmonary TB on HIV-1 disease. HIV-1 replication during dual HIV-1/TB infection is not amenable to virologic control by treatment of TB alone. Concurrent institution of highly active antiretroviral treatment needs to be evaluated in patients dually infected with pulmonary TB and HIV-1.
PMCID: PMC1287765  PMID: 16275944
13.  Changes in Human Immunodeficiency Virus Type 1 Fitness and Genetic Diversity during Disease Progression†  
Journal of Virology  2005;79(14):9006-9018.
This study examined the relationship between ex vivo human immunodeficiency virus type 1 (HIV-1) fitness and viral genetic diversity during the course of HIV-1 disease. Primary HIV-1 isolates from 10 patients at different time points were competed against control HIV-1 strains in peripheral blood mononuclear cell (PBMC) cultures to determine relative fitness values. Patient HIV-1 isolates sequentially gained fitness during disease at a significant rate that directly correlated with viral load and HIV-1 env C2V3 diversity. A loss in both fitness and viral diversity was observed upon the initiation of antiretroviral therapy. A possible relationship between genotype and phenotype (virus replication efficiency) is supported by the parallel increases in ex vivo fitness and viral diversity during disease, of which the correlation is largely based on specific V3 sequences. Syncytium-inducing, CXCR4-tropic HIV-1 isolates did have higher relative fitness values than non-syncytium-inducing, CCR5-tropic HIV-1 isolates, as determined by dual virus competitions in PBMC, but increases in fitness during disease were not solely powered by a gradual switch in coreceptor usage. These data provide in vivo evidence that increasing HIV-1 replication efficiency may be related to a concomitant increase in HIV-1 diversity, which in turn may be a determining factor in disease progression.
PMCID: PMC1168764  PMID: 15994794
14.  Sputum Cytokine Levels in Patients with Pulmonary Tuberculosis as Early Markers of Mycobacterial Clearance 
Sputum and serum from patients with active pulmonary tuberculosis (TB), healthy purified protein derivative-positive adults, and patients with bacterial pneumonia were collected to simultaneously assess local immunity in the lungs and peripheral blood. To determine whether cytokine profiles in sputum from TB patients and control subjects were a reflection of its cellular composition, cytospin slides were prepared in parallel and assessed for the presence of relative proportions of epithelial cells, neutrophils, macrophages, and T cells. Gamma interferon (IFN-γ) in sputum from TB patients was markedly elevated over levels for both control groups. With anti-TB therapy, IFN-γ levels in sputum from TB patients decreased rapidly and by week 4 of treatment were comparable to those in sputum from controls. Further, IFN-γ levels in sputum closely followed mycobacterial clearance. Although detected at fourfold-lower levels, IFN-γ immunoreactivities in serum followed kinetics in sputum. TNF-α, interleukin 8 (IL-8) and IL-6 also were readily detected in sputum from TB patients at baseline and responded to anti-TB therapy. In contrast to IFN-γ, however, TNF-α and IL-8 levels also were elevated in sputum from pneumonia controls. These data indicate that sputum cytokines correlate with disease activity during active TB of the lung and may serve as potential early markers for sputum conversion and response to anti-TB therapy.
PMCID: PMC120011  PMID: 12093679
15.  Human Immunodeficiency Virus Type 1 (HIV-1) Quasispecies at the Sites of Mycobacterium tuberculosis Infection Contribute to Systemic HIV-1 Heterogeneity 
Journal of Virology  2002;76(4):1697-1706.
We have recently reported an increased heterogeneity in the human immunodeficiency virus type 1 (HIV-1) envelope gene (env) in HIV-1-infected patients with pulmonary tuberculosis (TB) compared to patients with HIV-1 alone. This increase may be a result of dissemination of lung-derived HIV-1 isolates from sites of Mycobacterium tuberculosis infection and/or the systemic activation of the immune system in response to TB. To distinguish between these two mechanisms, blood and pleural fluid samples were obtained from HIV-1-infected patients with active pleural TB in Kampala, Uganda (CD4 cell counts of 34 to 705 cells/μl, HIV-1 plasma loads of 2,400 to 280,000 RNA copies/ml, and HIV-1 pleural loads of 7,600 to 4,500,000 RNA copies/ml). The C2-C3 coding region of HIV-1 env was PCR amplified from lysed peripheral blood mononuclear cells and pleural fluid mononuclear cells and reverse transcriptase-PCR amplified from plasma and pleural fluid HIV-1 virions of eight HIV-1 patients with pleural TB. Phylogenetic and phenetic analyses revealed a compartmentalization of HIV-1 quasispecies between blood and pleural space in four of eight patients, with migration events between the compartments. There was a trend for a greater genetic heterogeneity in the pleural space, which may be the result of an M. tuberculosis-mediated increase in HIV-1 replication and/or selection pressure at the site of infection. Collectively, these findings suggest that HIV-1 quasispecies in the M. tuberculosis-infected pleural space may leak into the systemic circulation and lead to increased systemic HIV-1 heterogeneity during TB.
PMCID: PMC135892  PMID: 11799165
16.  Influence of Polymorphism in the Genes for the Interleukin (IL)-1 Receptor Antagonist and IL-1β on Tuberculosis  
The Journal of Experimental Medicine  1999;189(12):1863-1874.
Several lines of evidence suggest that host genetic factors controlling the immune response influence infection by Mycobacterium tuberculosis. The proinflammatory cytokine interleukin (IL)-1β and its antagonist, IL-1Ra (IL-1 receptor agonist), are strongly induced by M. tuberculosis and are encoded by polymorphic genes. The induction of both IL-1Ra mRNA and secreted protein by M. tuberculosis in IL-1Ra allele A2–positive (IL-1Ra A2+) healthy subjects was 1.9-fold higher than in IL-1Ra A2− subjects. The M. tuberculosis–induced expression of mRNA for IL-1β was higher in subjects of the IL-1β (+3953) A1+ haplotype (P = 0.04). The molar ratio of IL-1Ra/IL-1β induced by M. tuberculosis was markedly higher in IL-1Ra A2+ individuals (P < 0.05), with minor overlap between the groups, reflecting linkage between the IL-1Ra A2 and IL-1β (+3953) A2 alleles. In M. tuberculosis–stimulated peripheral blood mononuclear cells, the addition of IL-4 increased IL-1Ra secretion, whereas interferon γ increased and IL-10 decreased IL-1β production, indicative of a differential influence on the IL-1Ra/IL-1β ratio by cytokines. In a study of 114 healthy purified protein derivative–reactive subjects and 89 patients with tuberculosis, the frequency of allelic variants at two positions (−511 and +3953) in the IL-1β and IL-1Ra genes did not differ between the groups. However, the proinflammatory IL-1Ra A2−/IL-1β (+3953) A1+ haplotype was unevenly distributed, being more common in patients with tuberculous pleurisy (92%) in comparison with healthy M. tuberculosis–sensitized control subjects or patients with other disease forms (57%, P = 0.028 and 56%, P = 0.024, respectively). Furthermore, the IL-1Ra A2+ haplotype was associated with a reduced Mantoux response to purified protein derivative of M. tuberculosis: 60% of tuberculin-nonreactive patients were of this type. Thus, the polymorphism at the IL-1 locus influences the cytokine response and may be a determinant of  delayed-type hypersensitivity and disease expression in human tuberculosis.
PMCID: PMC2192963  PMID: 10377182
interleukin 1 receptor; tuberculosis; susceptibility, disease; hypersensitivity, delayed; granuloma
17.  Interaction of Mycobacterium tuberculosis-Induced Transforming Growth Factor β1 and Interleukin-10 
Infection and Immunity  1999;67(11):5730-5735.
Mycobacterium tuberculosis is associated with the activation of cytokine circuits both at sites of active tuberculosis in vivo and in cultures of mononuclear cells stimulated by M. tuberculosis or its components in vitro. Interactive stimulatory and/or inhibitory pathways are established between cytokines, which may result in potentiation or attenuation of the effects of each molecule on T-cell responses. Here we examined the interaction of transforming growth factor β1 (TGF-β1) and interleukin-10 (IL-10) in purified protein derivative (PPD)-stimulated human mononuclear cell cultures in vitro. TGF-β1 induced monocyte IL-10 (but not tumor necrosis factor alpha) production (by 70-fold, P < 0.02) and mRNA expression in the absence but not in the presence of PPD. Both exogenous recombinant (r) IL-10 and rTGF-β1 independently suppressed the production of PPD-induced gamma interferon (IFN-γ) in mononuclear cells from PPD skin test-positive individuals. Synergistic suppression of IFN-γ in cultures containing both rTGF-β1 and rIL-10 was only seen when the responder cell population were peripheral blood mononuclear cells (PBMC) and not monocyte-depleted mononuclear cells and when PBMC were pretreated with rTGF-β1 but not with rIL-10. Suppression of PPD-induced IFN-γ in PBMC containing both rTGF-β1 (1 ng/ml) and rIL-10 (100 pg/ml) was 1.5-fold higher (P < 0.05) than cultures containing TGF-β1 alone and 5.7-fold higher (P < 0.004) than cultures containing IL-10 alone. Also, neutralization of endogenous TGF-β1 and IL-10 together enhanced PPD-induced IFN-γ in PBMC in a synergistic manner. Thus, TGF-β1 and IL-10 together potentiate the downmodulatory effect on M. tuberculosis-induced T-cell production of IFN-γ, and TGF-β1 alone enhances IL-10 production. At sites of active M. tuberculosis infection, these interactions may be conducive to the suppression of mononuclear cell functions.
PMCID: PMC96948  PMID: 10531222

Results 1-17 (17)