Thomas M. Daniel

Suppression of lymphocyte responses by tuberculous plasma and mycobacterial arabinogalactan. Monocyte dependence and indomethacin reversibility

During tuberculosis, exposure of monocytes to circulating factors may induce the suppressor activity observed in some anergic patients. To explore this possibility, we examined the effects of plasma pooled from 28 untreated tuberculosis (TB) patients and the mycobacterial cell wall polysaccharide D-arabino-D-galactan (AG) on the in vitro function of peripheral blood mononuclear cells (PBMC) from healthy donors. In the [3H] thymidine incorporation assay, stimulated responses of PBMC incubated in culture medium supplemented with TB plasma or co-cultured with 3.0 microgram/ml AG were depressed significantly when compared with control responses. Cytotoxicity and altered kinetics of stimulated DNA synthesis did not contribute to the observed suppression. TB plasma and AG-induced suppression of the PBMC response to purified protein derivative was monocyte dependent and indomethacin reversible. In addition, TB plasma and AG directly inhibited the phytohemagglutinin-stimulated responses of T lymphocytes. In a quantitative assay of monocyte attachment to plastic, both TB plasma and AG significantly increased monocyte adherence from basal levels. These effects on monocyte adherence were reversed with indomethacin or antibody to mycobacterial polysaccharide. In addition, TB plasma passed over an immunoabsorbent column of Sepharose-linked antibody to mycobacterial polysaccharide was depleted of the suppressive and monocyte-adherence augmenting factors. 3.0 microgram/ml AG stimulated a fivefold increase in prostaglandin E2 production by cultured mononuclear cells. Our data suggest that AG circulating alone or bound in immune complexes may account for the observed effects of TB plasma. Similar in vivo exposure may contribute to the cell-mediated suppression of lymphocyte responses in tuberculosis.

Induction of monocyte expression of tumor necrosis factor alpha by the 30-kD alpha antigen of Mycobacterium tuberculosis and synergism with fibronectin.

Native 30-kD antigen, also known as alpha antigen, is a fibronectin-binding protein that is secreted by live Mycobacterium tuberculosis. This antigen may play an important biological role in the host-parasite interaction since it elicits delayed type hypersensitivity response and protective immunity in vivo and T lymphocyte blastogenesis and IFN-gamma production in vitro. In the present study, we show that, TNF-alpha protein is produced in monocyte culture supernatants in response to 30-kD antigen and the level is as high as that to purified protein derivative of M. tuberculosis. This stimulatory effect was not due to contamination with either bacterial lipopolysaccharide or mycobacterial lipoarabinomannan. The preincubation of monocytes with plasma fibronectin significantly enhanced the release of TNF-alpha into the culture supernatants in response to 30-kD antigen. This effect was blocked by polygonal antibody to plasma fibronectin. In contrast, the monocytic cell line U937 failed to release TNF-alpha protein in the culture supernatants in response to 30-kD antigen with or without preincubation with plasma fibronectin. To determine whether this observation was due to differential binding of the 30-kD to fibronectin on these cells, a cell based ELISA was used. Pretreatment of monocytes with fibronectin enhanced their binding of the 30-kD antigen. U937 cells bound the 30-kD antigen weakly with or without fibronectin pretreatment. These results indicate that 30-kD antigen which is a known secretary antigen of M. tuberculosis is a stimulus for human monocytes to express TNF-alpha and that stimulatory effect may be mediated through plasma fibronectin.

Absence of Mycobacterium avium Complex Disease in Patients with Aids in Uganda

The absence of disease due to Mycobacterium avium in Ugandan patients with AIDS, which we previously observed in a blood culture study, has been confirmed and our observations have been extended to 165 additional clinical isolates. Fourteen soil and water samples from the Ugandan environment have been cultured and revealed a high frequency of isolation of M. avium. The absence of M. avium complex disease in Uganda remains unexplained.

Evaluation of Mycobacterial Antigens in an Enzyme-Linked Immunosorbent Assay (ELISA) for the Serodiagnosis of Tuberculosis

Five mycobacterial antigens were compared in an enzyme-linked immunosorbent assay (ELISA) for the serodiagnosis of tuberculosis. The antigens studied were an unheated sterile culture filtrate of Mycobacterium tuberculosis, tuberculin purified protein derivative (PPD) from M. tuberculosis (PPDa), purified cytoplasmic protein antigens 5 and 6 from M. tuberculosis, and a PPD prepared from M. kansasi (PPDk). Multivariate analysis of variance showed that geometric mean titres obtained with each of the antigens in ELISA were significantly different in tuberculosis patients and in control groups. The covariation of the ELISA results with the five antigens was highly interdependent. Analysis of receiver operating characteristics revealed that the most accurate test was obtained with antigen 5. M. tuberculosis PPD, M. tuberculosis antigen 6, and M. tuberculosis culture filtrate were, in descending order, less accurate.

Reduced sensitivity of tuberculosis serodiagnosis in patients with AIDS in Uganda

SETTING The diagnostic utility of serodiagnosis of tuberculosis in HIV-infected persons was studied in Kampala, Uganda. OBJECTIVE This study was undertaken to evaluate the utility of a recently described serologic assay for the diagnosis of tuberculosis in HIV-infected patients. DESIGN The study was undertaken as a cross-sectional survey of 349 subjects, including human immunodeficiency virus-infected and uninfected patients with tuberculosis and control subjects. Serum from each subject was assayed by enzyme-linked immunosorbent assay (ELISA) for IgG antibody to the 30,000 dalton antigen of Mycobacterium tuberculosis. RESULTS Test sensitivity dropped from 0.62 in non HIV-infected tuberculous patients to 0.28 in HIV-infected patients. CONCLUSIONS ELISA serodiagnosis of tuberculosis may have a markedly decreased utility in populations where HIV infection is prevalent.

Estimation of the Annual Risk of Tuberculous Infection for White Men in the United States

The annual risk of tuberculous infection for white men in the United States was estimated from published tuberculin surveys and found to be related to tuberculosis incidence as reflected in the annual case rate during the past 3 decades, with a constant ratio of approximately 150. It is currently estimated to be 0.03%/year. The technique developed for this estimation is not complex and should be applicable to other segments of the population for which suitable data are available.

Isolation and characteristics of Mycobacterium avium complex from water and soil samples in Uganda

SETTING Mycobacterium avium complex organisms have not been isolated from late stage AIDS patients in Uganda. This could possibly be due to the absence of M. avium complex in the Uganda environment. OBJECTIVE AND DESIGN Determine whether M. avium complex organisms could be isolated from water and soils collected in the living environment of Ugandan AIDS patients. RESULTS Representatives of the M avium complex were isolated from 3 of 7 (43%) water and 3 of 7 (43%) soil samples collected in Kampala, Uganda. The average number of colony-forming units per ml water was 3.3 and average colony-forming units per gram of soil was 7825. In terms of growth characteristics, antimicrobial susceptibility patterns, and the presence or absence of plasmids and IS901, Ugandan M. avium complex isolates were similar to those isolated from the US and European AIDS patients and their environment. CONCLUSIONS M. avium complex organisms sharing genetic and physiological characteristics of M. avium complex isolates recovered from patients with AIDS can be isolated from water and soil samples in Uganda.

The impact of tuberculosis on civilization

Tuberculosis is an ancient disease that has spread in epidemic form among susceptible peoples but has had a little demographic or political impact on the populations it has inflicted. The disease continues to have a large economic impact on societies in which it is prevalent. Tuberculosis has left its mark on human creativity; on the lives of individuals in music, art, and literature; and dramatically on the advance of biomedical science and healthcare.

Bacille Calmette Guérin immunization of health care workers exposed to multidrug-resistant tuberculosis: A decision analysis

SETTING North American health care workers with exposure to multidrug-resistant tuberculosis. OBJECTIVE To evaluate the relative utilities of bacille Calmette Guérin (BCG) immunization and post-infection chemoprophylaxis for the protection of health care workers exposed to multidrug-resistant Mycobacterium tuberculosis. DESIGN Decision analysis using SMLTREE software and published data for probabilities. RESULTS BCG vaccination was preferred by a small margin over post-infection chemoprophylaxis. Sensitivity analysis revealed that possible changes in probability values used tended to tilt the result towards use of BCG vaccination. The threshold for protective efficacy of BCG vaccination was 26%. CONCLUSIONS BCG vaccination should be considered for health care workers in environments where there is a substantial risk of exposure to multidrug-resistant tuberculosis.

Clinical evaluation of the diagnostic value of measuring IgG antibody to 3 mycobacterial antigen preparations in the capillary blood of children with tuberculosis and control subjects

SETTING Department of Paediatrics in a University Hospital. OBJECTIVE To evaluate ABC-ELISA as serodiagnostic tests for tuberculosis in children. DESIGN An avidin-biotin-peroxidase conjugated anti-human immunoglobulin (ABC) enzyme-linked immunosorbent assay (ELISA) was established to measure serum immunoglobulin G (IgG) antibodies to polymerized old tuberculin (OT), tuberculin purified protein derivative (PPD) and the 30,000 dalton (30 kDa) native antigen of Mycobacterium tuberculosis, in 122 tuberculosis patients and 187 healthy children. RESULTS In those patients who had received less than 3 months of chemotherapy the sensitivities of the tests based on OT, PPD and the 30 kDa antigen were 40.3%, 50.0% and 36.1% respectively; the positive predictive values were 92.6%, 94.7% and 93.8% respectively and the negative predictive values were 58.6%, 62.9% and 57.2% respectively. CONCLUSION The ABC-ELISA may be useful for the diagnosis of pulmonary and extrapulmonary tuberculosis in groups of children with a high prior probability of tuberculosis. Antibodies to the 30 kDa antigen persisted longer than did those to OT and PPD.