Faculty Bibliography

Local cellular immune responses may affect presentation and outcome in tuberculosis (TB). To investigate this hypothesis, we performed bronchoalveolar lavage (BAL) on 30 patients with untreated pulmonary tuberculosis and assessed the type of cellular inflammatory response and cytokine production. We then correlated BAL findings and cytokine production with clinical findings. We also performed BAL on a subset of patients to examine changes in cytokine production by BAL cells over time. We found that at presentation patients with less clinically and radiographically advanced TB (smear-negative, noncavitary disease) had a local immune response characterized by a predominance of lymphocytes. Furthermore, BAL cells from these patients secreted interferon (IFNgamma), and not Interleukin-4, suggesting a Th 1-type lymphocytic response. In patients with smear-positive and/or cavitary disease, macrophages or polymorphonuclear leukocytes were the predominant BAL cell type, but with treatment and clinical improvement these patients went on to recruit IFNgamma producing cells to the lung. We conclude that the type of cellular immune response that occurs locally in the lung may affect presentation and outcome in pulmonary TB, and an understanding of the development of this response may lead to insights into pathogenesis and novel therapies for TB

BACKGROUND: Multidrug-resistant tuberculosis (MDR-TB) is associated with substantial morbidity, despite drug therapy. Interferon-gamma, a cytokine produced mainly by CD4 T lymphocytes, can activate alveolar macrophages, important effector cells in host immunity against Mycobacterium tuberculosis. We investigated safety and tolerability of aerosolised interferon-gamma in patients with MDR-TB, and assessed its efficacy in terms of sputum-smear grades. METHODS: We did an open-label trial of aerosol interferon-gamma given to five patients with smears and cultures positive for pulmonary MDR-TB, despite documented adherence to therapy. The patients received aerosol interferon-gamma 500 micrograms three times a week for 1 month. Safety and tolerability were assessed, and, as well as routine clinical assessments, sputum samples for smear and culture were collected at entry and weekly. Computed tomography scans of the chest were done at baseline and after therapy ended. FINDINGS: Interferon-gamma was well tolerated by all patients. In all five, bodyweight stabilised or increased. Sputum acid-fast-bacillus smears became negative in all patients, and the time to positive culture increased (from 17 to 24 days, not significant), which suggested that the mycobacterial burden had decreased. The size of cavitary lesions was reduced in all patients, 2 months after treatment had ended. INTERPRETATION: Preliminary data suggest that aerosol interferon-gamma is a well-tolerated treatment that may be useful as adjunctive therapy in patients with MDR-TB who are otherwise not responding well to therapy

We investigated the in vivo effect of coinfection of Mycobacterium tuberculosis on human immunodeficiency virus type 1 (HIV-1) replication using bronchoalveolar lavage (BAL) of 11 HIV-1-infected patients with pulmonary tuberculosis and 10 patients with no lung disease. Lung segments involved with pulmonary tuberculosis had significantly elevated HIV-1 branched DNA (bDNA) levels and p24 in BAL compared with lung segments uninvolved with tuberculosis or with BAL from patients with no lung disease. The BAL viral burden was higher than plasma HIV-1 in tuberculosis patients, indicating local production of virus. BAL HIV-1 bDNA declined over the course of treatment for tuberculosis in three patients who underwent serial bronchoscopies. Tumor necrosis factor-alpha (TNF-alpha) and HIV-1 bDNA particles were strongly correlated (r2 = 0.9, p < 0.01) in lung segments involved with tuberculosis. The deduced amino acid sequence of HIV-1 gp120 V3 region from involved segments of three patients with pulmonary tuberculosis showed basic substitutions associated with altered viral phenotype. Phylogenetic analysis of V3 sequences demonstrated that BAL HIV-1 RNA had diverged from plasma. These data support the conclusion that pulmonary tuberculosis enhances local HIV-1 replication in vivo

BACKGROUND: There is a need for rapid diagnosis of pulmonary tuberculosis. We have previously used a PCR to detect circulating Mycobacterium tuberculosis DNA in blood samples from patients (mostly HIV-infected) with pulmonary tuberculosis. We have now prospectively investigated the role of this blood-based PCR assay for diagnosis of this disease in a clinical setting. METHODS: Our PCR assay is specific for the IS6110 insertion element of the M tuberculosis complex of organisms. We used it to test peripheral blood from 88 consecutive patients admitted to a chest ward with suspected pulmonary tuberculosis. Personnel who carried out the assay did not know the results of any clinical investigations and ultimate diagnosis, and clinicians did not know the PCR results. Results of the PCR assay were compared with the final clinical diagnosis. A subgroup of 15 patients had blood samples assayed serially to track the PCR signal over time. FINDINGS: 41 patients had a final clinical diagnosis of tuberculosis, and the cases were typical of those seen at our hospital: HIV infection was common, and most cases were not sputum-smear positive for acid-fast bacilli. The PCR assay correctly identified 39 of 41 patients with proven pulmonary tuberculosis, 26 (63%) of whom were sputum-smear negative. There were five patients in whom a positive PCR result did not accord with the final clinical diagnosis, and two of the 44 negative PCR results were classified as false negatives. The overall sensitivity and specificity of the PCR assay for a diagnosis of tuberculosis was 95% and 89%, respectively. In 15 patients with pulmonary tuberculosis and a positive blood assay,the PCR result remained positive after 1 month of therapy, but had reverted to negative in 13 of the 15 by 4 months of therapy. INTERPRETATION: We conclude that peripheral-blood-based PCR detection for the diagnosis of tuberculosis is a technically feasible approach that has a potentially important role in the diagnosis of pulmonary tuberculosis

Despite the importance of tuberculosis as the leading cause of death due to infectious disease in the world, it has only been recently that an understanding of the human host response in this infection has begun to emerge. The key components of this response are cytokines and components of cellular immunity, predominantly T-lymphocytes and macrophages. Though the relationships among the components of the immune response are complex, it seems likely that in response to mycobacterial infection associated with active disease, cytokines such as TNF-alpha and IL-1 beta are produced; these cytokines serve to recruit more lymphocytes, generally of the T(H) (T helper) phenotype, which then produces substances such as the macrophage activating factor interferon-gamma. Macrophages activated by IFN-gamma ar thus stimulating to enhance intracellular killing of mycobacteria. The role of other cytokines, such as IL-6 and IL-8, both of which are induced by M. tuberculosis or its cell was components, is less clear. Further elucidation of the human host response to tuberculosis should help in the development of new vaccines and treatment strategies

Many patients with obstructive sleep apnea syndrome (OSAS), despite therapy with nasal continuous positive airway pressure (CPAP), have persisting daytime somnolence that may be due to a persistently elevated upper-airway resistance associated with electroencephalographic (EEG) arousals. We tested the hypothesis that elevated upper-airway resistance can be inferred from the contour of the inspiratory flow tracing obtained from a conventional CPAP circuit. This may provide a noninvasive method for determining optimal CPAP. Data were collected during a CPAP titration of an upper-airway model and in eight patients with OSAS. Estimated inspiratory resistance was calculated from esophageal pressure, CPAP mask pressure, and inspiratory flow. At high CPAP, resistance was low and inspiratory flow contour was found to be rounded. At low CPAP, resistance was high and flow contour developed a plateau suggesting flow limitation. We also noted that the CPAP pressure at which high resistance developed, and at which flow limitation appeared, showed hysteresis. We conclude that when respiration is stable, the contour of inspiratory flow tracing from a CPAP system can be used to infer the presence of elevated upper-airway resistance and flow limitation. Optimizing flow contour may be an alternative to eliminating apneas in evaluation of the optimal therapeutic level of CPAP in OSAS

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