Faculty Bibliography

The host response to Mycobacterium tuberculosis includes granuloma formation at sites of infection and systemic symptoms. Cytokines have been identified by immunohistochemistry in granulomas in animal models of bacillus Calmette-Guerin (BCG) infection and are released by mononuclear phagocytes upon stimulation by mycobacterial proteins. In this regard, the cytokine interleukin 6 (IL-6) may play a role in the clinical manifestations and pathological events of tuberculosis infection. We have demonstrated that lipoarabinomannan (LAM) from the mycobacterial cell wall, which was virtually devoid of lipopolysaccharide (LPS), stimulated mononuclear phagocytes to release IL-6 in a dose-response manner. LAM and LPS were potent inducers of IL-6 gene expression in peripheral blood monocytes. Both LAM- and LPS-inducible IL-6 promoter activity was localized to a DNA fragment, positions -158 to -49, by deletion analysis and chloramphenicol acetyltransferase assay. Two nuclear factor NF-IL6 (positions -153 to -145 and -83 to -75) and one nuclear factor NF-kappa B (positions -72 to -63) motifs are present within this fragment. Site-directed mutagenesis of one or more of these motifs within the IL-6 promoter demonstrated that each has positive regulatory activity and that they could act in a function- and orientation-independent manner. Deletion of all three elements abolished inducibility of IL-6 promoter activity by both LAM and LPS. We conclude that the NF-IL6 and NF-kappa B sites mediate IL-6 induction in response to both LPS and LAM, acting as bacterial or mycobacterial response elements

Sputum examination for rapid diagnosis of pulmonary tuberculosis is not always satisfactory. We examined peripheral blood with the polymerase chain reaction (PCR). Blood samples were collected from 8 consecutive patients with suspected pulmonary tuberculosis and from 18 healthy controls, half of whom were tuberculin skin-test positive. All 8 patients had evidence of circulating Mycobacterium tuberculosis DNA in the lymphocyte fraction of peripheral blood, and positive sputum cultures indicating active pulmonary tuberculosis. None of the healthy controls had positive PCR results. This PCR technique may prove useful for the rapid diagnosis of tuberculosis

The host response to Mycobacterium tuberculosis is characterized by interactions between mononuclear cells, with recruitment and fusion of these cells culminating in granuloma formation. In addition, the host response to M. tuberculosis requires CD4+ T-cell reactivity, mediated by antigen-independent as well as antigen-dependent mechanisms. Thus, we hypothesized that cell adhesion molecules such as intercellular adhesion molecule 1 (ICAM-1; CD54) would participate in the response to infection with M. tuberculosis. Exposure of THP-1 cells derived from a monocyte/macrophage cell line to M. tuberculosis (1:1 bacterium/cell ratio) elicited a sustained increase (660% +/- 49% above resting level) in the expression of ICAM-1 that continued for at least 72 h. Neither the expression of vascular cell adhesion molecule 1 (VCAM-1; CD106) nor that of the integrins lymphocyte function-associated antigen 1 (LFA-1; CD11a/CD18) or CR3 (CD11b/CD18) was increased to a similar extent at corresponding time points. The increase in ICAM-1 protein expression was accompanied by an increase in steady-state mRNA (Northern [RNA] analysis). Neutralizing monoclonal antibodies directed against tumor necrosis factor alpha but not interleukin 1 alpha or interleukin 1 beta substantially abrogated the response to M. tuberculosis consistent with a paracrine or autocrine response. Continuous upregulation of the expression of ICAM-1 on mononuclear phagocytes induced by M. tuberculosis may mediate the recruitment of monocytes and enhance the antigen presentation of M. tuberculosis, thus permitting the generation and maintenance of the host response

Tuberculosis (TB) is one of the most important infections worldwide, with an estimated incidence of 10 million active cases per year. Rifampicin is a key component of the first-line therapy used in the treatment of tuberculosis. In Escherichia coli and Mycobacterium leprae, rifampicin has been shown to inhibit the beta subunit of RNA polymerase. The gene (rpoB) encoding this enzyme has been described in both species. We report the isolation of the homologous functional rifampicin resistance gene from M. tuberculosis. A library was constructed with 15 to 25 kb BamHI-digested DNA fragments from a rifampicin-resistant M. tuberculosis clinical isolate that was ligated into an E. coli-mycobacterial shuttle plasmid. Southern analysis of BamHI-digested DNA from 200 recombinant plasmids was performed and filters were hybridized to a 411 bp fragment of the beta subunit of RNA polymerase from M. tuberculosis. Only DNA from one plasmid (#86) hybridized, which suggested that the gene is found as a single copy per genome. This plasmid was able to transfer rifampicin resistance to sensitive M. smegmatis and thus codes for a functional genetic unit. Sequence analysis in the expected 'hotspot' region in eight rifampicin-resistant M. tuberculosis strains (including one multidrug-resistant strain) revealed two novel mutations as well as others previously described

OBJECTIVES: The purpose of the study was to describe demographic and clinical characteristics of patients at the only long-term care facility for homeless men with tuberculosis in New York City, and to evaluate the outcome of a directly observed therapy program for these men. METHODS: The study population included residents at the 'tuberculosis unit' for men in the New York City municipal shelter system. A cross-sectional survey described the characteristics of 76 men in the unit during November 1991. A retrospective cohort study evaluated 104 consecutive admissions to the facility from October 1, 1990, through March 30, 1991, and determined the outcome of directly observed therapy. RESULTS: Cross-sectional survey (n = 76). The median age was 43 years (range, 25 to 60 years); 67 patients (88%) had pulmonary tuberculosis. Among 58 isolates of Mycobacterium tuberculosis, eight were resistant to one drug (14%) and an additional nine were resistant to at least two drugs (16%). A history of previous treatment was associated with an odds ratio of 5.1 for having multiple drug-resistant tuberculosis (exact 95% confidence interval, 0.8 to 53.5). Retrospective cohort (n = 104). Excluding 21 men whose care was transferred to other agencies or institutions, 39 (47%) of 83 subjects completed or were still receiving treatment after 12 months and 44 (53%) of 83 subjects failed to complete the program. CONCLUSIONS: As expected, previous treatment for tuberculosis among homeless men is associated with an increased risk of having multiple-drug resistance. A directly observed therapy program successfully treated less than half of the enrolled subjects. Increased efforts are needed to control the spread of tuberculosis among homeless individuals

Insulin-like growth factor (IGF) I has important growth regulatory functions in normal growth and development. IGF-I is also a mitogen for a number of cancer cell lines; however, its autocrine effect has not been well established. In this study, the expression of IGF-I, its receptor, and its major serum-binding protein were examined in 5 normal human mesothelial (NHM) cell samples and 11 pleural mesothelioma cell lines. All NHM cells and mesothelioma cell lines expressed IGF-I, IGF-binding protein 3 (IGFBP-3), and IGF-I receptor mRNA by either Northern blot or reverse transcription polymerase chain reaction analysis. IGF-I (0.136 +/- 0.024 ng/ml, mean +/- SEM) and IGFBP-3 (18.5 +/- 3.2 ng/ml) proteins were readily detected in the conditioned medium of mesothelioma cell lines but were not greater than corresponding measurements in that of NHM cells (IGF-I, 0.120 +/- 0.080 ng/ml; IGFBP-3, 15.9 +/- 1.3 ng/ml). Exogenous recombinant IGF-I stimulated cell proliferation of NHM cells, demonstrating the presence of a functional IGF-I receptor. Our results suggest that IGF-I may function as an autocrine growth stimulus in normal proliferating mesothelial cells, which may contribute to their malignant transformation