Variants of the human NRAMP1 gene and altered human immunodeficiency virus infection susceptibility.

In a population-based case-control study, 182 human immunodeficiency virus (HIV)-positive persons and 135 healthy control subjects were enrolled from the metropolitan area of Medellin, Colombia. Four genotypes of the natural resistance-associated macrophage protein l (NRAMP1) gene (5' GT repeat, 274C/T, 469+14G/T, and 823C/T) were associated with altered risk of HIV infection (P=.013,.015,.020, and. 035, respectively). Three of these markers (5' [GT]n, 274C/T, 469+14G/T) are in strong linkage disequilibrium, and genotypes of these markers are associated with reduced risk of HIV infection with relative risks (RRs) of 0.35 (95% confidence interval [CI], 0.14-0.91), 0.31 (CI, 0.10-0.93), and 0.24 (CI, 0.08-0.72), respectively. Conversely, heterozygosity at the fourth independent marker (823C/T) was associated with increased risk of HIV infection (RR, 2.29; CI, 1.06-4.92). These findings suggest that NRAMP1 modifies risk of HIV infection.

Inhibition of virulent Mycobacterium tuberculosis by Bcg(r) and Bcg(s) macrophages correlates with nitric oxide production.

The Nramp1 gene controls macrophage resistance or susceptibility to several intracellular microorganisms; however, there is conflicting evidence regarding its role during infection with virulent Mycobacterium tuberculosis. Nitric oxide (NO) is a potent antimycobacterial agent produced by macrophages, which is also regulated by Nramp1. The in vitro ability of B10R (resistant) and B10S (susceptible) murine macrophages to inhibit M. tuberculosis H37Rv and to produce NO in response to infection and interferon-gamma (IFN-gamma) was compared. Infected B10R macrophages inhibited [3H]uracil incorporation by M. tuberculosis and produced higher amounts of NO than did B10S macrophages. IFN-gamma increased the inhibitory activity of both cells. Inhibition of M. tuberculosis by IFN-gamma-activated B10R macrophages was reversed by N(G)-monomethyl-L-arginine (N(G)MMA). L-arginine restored NO production and increased the antimycobacterial activity by IFN-gamma-stimulated N(G)MMA-treated macrophages. The Bcg/Nramp1 gene may regulate macrophage resistance or susceptibility to virulent M. tuberculosis by a differential capability of these cells to produce NO.

Tuberculin skin test and CD+4/CD8+ T cell counts in adults infected with the human immunodeficiency virus in Medellin, Colombia

To evaluate the effect of BCG vaccination and T lymphocyte subpopulations on the reactivity to the tuberculin skin test, 113 asymtomatic HIV+ individuals were tuberculin tested by intradermal injection of 5TU of purified protein derivate and the levels of circulating lymphocyte (CD3, CD4 and CD8) subpopulations determined by indirect immunoflurescence. Ninety-two per cent of the subjects included in the study, were males. The mean age of the group was 32.1ñ7.4 years. Sixty-two percent presented a BCG scar. However, only 22 per cent exhibited positive tuberculin reations (ò5mm) irrespective of the presence of the BCG scar. Tuberculin positive individuals exhibited higher CD4+ cell counts (p=0.004) and CD4+/CD8+ ratios (p=0.006) than tuberculin negative (<5mm) HIV+ individuals. The number of individuals with positive tuberculin reactions was significantly higher in subjects with more than 500 CD4+ lymphocytes/µl (p=0.02) or CD4+/CD8+ ratios ò1.12 (p=0.002). These results suggest that a prior BCG vaccination does not influence the reactivity to the tuberculin skin test in HIV+ asymptomatic individuals and that the number of CD4+ lymphocytes and the CD4+ lymphocytes and the CD4+/CD8+ ratio positively correlate with the tuberculin reactivity.

Tuberculin skin test and CD4+/CD8+ T cell counts in adults infected with the human immunodeficiency virus in Medellín, Colombia.

To evaluate the effect of BCG vaccination and T lymphocyte subpopulations on the reactivity to the tuberculin skin test, 113 asymptomatic HIV+ individuals were tuberculin tested by intradermal injection of 5TU of purified protein derivative and the levels of circulating lymphocyte (CD3, CD4 and CD8) subpopulations determined by indirect immunofluorescence. Ninety-two percent of the subjects included in the study were males. The mean age of the group was 32.1 +/- 7.4 years. Sixty-two percent presented a BCG scar. However, only 22% exhibited positive tuberculin reactions (> or = 5 mm) irrespective of the presence of the BCG scar. Tuberculin positive individuals exhibited higher CD4+ cell counts (p = 0.004) and CD4+/CD8+ ratios (p = 0.006) than tuberculin negative (< 5 mm) HIV+ individuals. The number of individuals with positive tuberculin reactions was significantly higher in subjects with more than 500 CD4+ lymphocytes/microliter (p = 0.02) or CD4+/CD8+ ratios > or = 1.12 (p = 0.002). These results suggest that a prior BCG vaccination does not influence the reactivity to the tuberculin skin test in HIV+ asymptomatic individuals and that the number of CD4+ lymphocytes and the CD4+/ CD8+ ratio positively correlate with the tuberculin reactivity.

Failure to induce nitric oxide production by human monocyte-derived macrophages. Manipulation of biochemical pathways.

Production of nitrix oxide (NO-) by human macrophages is controversial. In the present study, the ability of human monocyte-derived macrophages (M phi) to produce NO- in response to M phi modulators was tested. M phi cultured for up to nine days and stimulated for 48 with different concentrations of LPS and/or IFN-gamma failed to produce significant amounts of NO2- compared to unstimulated cultures. Inhibition of the cyclo-oxygenase pathway with indomethacin did not increase NO2- production by LPS stimulated M phi. Since human M phi lack biopterin, needed for NO- synthesis by murine M phi, human M phi stimulated with LPS plus IFN-gamma were additionally cultured in the presence of neopterin or biopterin. These treatments did not induce NO2- production. Furthermore, simultaneous treatment with indomethacin and neopterin or biopterin also failed to induce NO2- production. However, human M phi, stimulated with IFN-gamma and LPs, produced TNF-alpha suggesting that the lack of increment in NO2- production was not due to an absence of response of M phi to the stimuli used. As an indirect approach to explore the NO- production, human M phi were infected with virulent Mycobacterium tuberculosis H37Rv and simultaneously treated with the competitive inhibitor NGmonomethyl-L-arginine (NGMMA). Mycobacterial intracellular replication was measured by 3H-uracil incorporation. NGMMA did not have any effect on mycobacterial replication. These results further suggest that human M phi do not produce NO- at least by the inducible pathway.

Evidence that active and stable E-rosette forming cells belong to different human T lymphocyte subpopulations.

Human T Lymphocytes form spontaneous E-rosettes with sheep erythrocytes. Cells with high affinity E-receptors can be differentiated by their formation of active (aE) or stable (sE)-rosettes; therefore, experiments were performed in order to determine if active and stable E-rosettes are formed by different populations of T lymphocytes. "Enriched" and "depleted" fractions of aE-RFC were separated on Ficoll-Hypaque after fresh peripheral blood lymphocytes were mixed with SRBC under aE-rosette conditions. Enrichment of aE-RFC did not induce a simultaneous increase in the number of sE-RFC. Furthermore, upon incubation with Con A, a significant increase in the percentage of sE-RFC was detected in the aE-RFC "depleted" preparation. Fractionation of lymphocytes which had been cultured with Con A into sE-"enriched" and "depleted" populations again showed that aE-and sE-RFC do not co-separate in to the same fractions. Analysis of T cell-enriched cultures, prepared from peripheral blood lymphocytes either by rosetting with SRBCaet or fractionation on nylon wool columns, which were stimulated with Con A and then fractionated into aE-or sE- "enriched" and "depleted" populations clearly showed that enrichment of aE-RFC results in a decrease in the number of sE-RFC and viceversa. These data strongly support the idea that cells forming active and stable E-rosettes belong to different populations of human T lymphocytes.

Formation of total, active and stable E-rosettes by human lymphocytes stimulated with con A derivatives.

Peripheral blood lymphocytes from healthy human volunteers where incubated for 48 hr with 10 micrograms/ml of native Con A or its dimeric derivatives, succinyl- and acetyl-Con A. The percentage of total-active and stable E-rosettes were determined before and after incubation. There were no differences among the three forms of the lectin. Stable E-rosettes exhibited the most dramatic effects from Con A stimulation. They increased from approximately 2% in control cultures to 20-25% in stimulated cultures. Treatment with the Con A inhibitor alpha-Methyl-D-mannoside after Con A stimulation did not affect the rosette formation. Our results suggest that redistribution of membrane receptors on stimulated lymphocytes is not responsible for increased E-rosette formation after Con A stimulation since dimeric forms of Con A are not able to induce membrane receptor redistribution.