Sarcoidosis is a disease of unknown etiology characterized by noncaseating epithelioid granulomas, oligoclonal CD4+ T cell infiltrates, and immune complex formation. To identify pathogenic antigens relevant to immune-mediated granulomatous inflammation in sarcoidosis, we used a limited proteomics approach to detect tissue antigens that were poorly soluble in neutral detergent and resistant to protease digestion, consistent with the known biochemical properties of granuloma-inducing sarcoidosis tissue extracts. Tissue antigens with these characteristics were detected with immunoglobulin (Ig)G or F(ab′)2 fragments from the sera of sarcoidosis patients in 9 of 12 (75%) sarcoidosis tissues (150–160, 80, or 60–64 kD) but only 3 of 22 (14%) control tissues (all 62–64 kD; P = 0.0006). Matrix-assisted laser desorption/ionization time of flight mass spectrometry identified Mycobacterium tuberculosis catalase–peroxidase (mKatG) as one of these tissue antigens. Protein immunoblotting using anti-mKatG monoclonal antibodies independently confirmed the presence of mKatG in 5 of 9 (55%) sarcoidosis tissues but in none of 14 control tissues (P = 0.0037). IgG antibodies to recombinant mKatG were detected in the sera of 12 of 25 (48%) sarcoidosis patients compared with 0 of 11 (0%) purified protein derivative (PPD)− (P = 0.0059) and 4 of 10 (40%) PPD+ (P = 0.7233) control subjects, suggesting that remnant mycobacterial catalase–peroxidase is one target of the adaptive immune response driving granulomatous inflammation in sarcoidosis.

Cytotoxic effector phenotype and function of MHC-restricted Mycobacterium tuberculosis (MTB)-reactive CD4+ and CD8+ T lymphocytes were analyzed from healthy tuberculin skin test-positive persons. After stimulation in vitro with MTB, both CD4+ and CD8+ T cells up-regulated mRNA expression for granzyme A and B, granulysin, perforin, and CD95L (Fas ligand). mRNA levels for these molecules were greater for resting CD8+ than CD4+ T cells. After MTB stimulation, mRNA levels were similar for both T cell subsets. Increased perforin and granulysin protein expression was confirmed in both in CD4+ and CD8+ T cells by flow cytometry. Both T cell subsets lysed MTB-infected monocytes. Biochemical inhibition of the granule exocytosis pathway in CD4+ and CD8+ T cells decreased cytolytic function by >90% in both T cell subsets. Ab blockade of the CD95-CD95L interaction decreased cytolytic function for both T cell populations by 25%. CD4+ and CD8+ T cells inhibited growth of intracellular MTB in autologous monocytes by 74% and 84%, respectively. However, inhibition of perforin activity, the CD95-CD95L interaction, or both CTL mechanisms did not affect CD4+ and CD8+ T cell mediated restriction of MTB growth. Thus, perforin and CD95-CD95L were not involved in CD4+ and CD8+ T cell mediated restriction of MTB growth.

The alternate RNA polymerase sigma factor gene, sigF, which is expressed in stationary phase and under stress conditions in vitro, has been deleted in the virulent CDC1551 strain of Mycobacterium tuberculosis. The growth rate of the ⌬sigF mutant was identical to that of the isogenic wild-type strain in exponential phase, although in stationary phase the mutant achieved a higher density than the wild type. The mutant showed increased susceptibility to rifampin and rifapentine. Additionally, the ⌬sigF mutant displayed diminished uptake of chenodeoxycholate, and this effect was reversed by complementation with a wild-type sigF gene. No differences in short-term intracellular growth between mutant and wild-type organisms within human monocytes were observed. Similarly, the organisms did not differ in their susceptibilities to lymphocyte-mediated inhibition of intracellular growth. However, mice infected with the ⌬sigF mutant showed a median time to death of 246 days compared with 161 days for wild-type strain-infected animals (P < 0.001). These data indicate that M. tuberculosis sigF is a nonessential alternate sigma factor both in axenic culture and for survival in macrophages in vitro. While the ⌬sigF mutant produces a lethal infection of mice, it is less virulent than its wild-type counterpart by time-to-death analysis.

h Despite the widespread use of the Mycobacterium bovis BCG vaccine, there are more than 9 million new cases of tuberculosis (TB) every year, and there is an urgent need for better TB vaccines. TB vaccine candidates are selected for evaluation based in part on the detection of an antigen-specific gamma interferon (IFN-␥) response. The measurement of mycobacterial growth in blood specimens obtained from subjects immunized with investigational TB vaccines may be a better in vitro correlate of in vivo vaccine efficacy. We performed a clinical study with 30 United Kingdom adults who were followed for 6 months to evaluate the abilities of both a whole-blood-and a novel peripheral blood mononuclear cell (PBMC)-based mycobacterial growth inhibition assay to measure a response to primary vaccination and revaccination with BCG. Using cryopreserved PBMCs, we observed a significant improvement in mycobacterial growth inhibition following primary vaccination but no improvement in growth inhibition following revaccination with BCG (P < 0.05). Mycobacterial growth inhibition following primary BCG vaccination was not correlated with purified protein derivative (PPD) antigen-specific IFN-␥ enzyme-linked immunospot (ELISPOT) responses. We demonstrate that a mycobacterial growth inhibition assay can detect improved capacity to control growth following primary immunization, but not revaccination, with BCG. This is the first study to demonstrate that an in vitro growth inhibition assay can identify a difference in vaccine responses by comparing both primary and secondary BCG vaccinations, suggesting that in vitro growth inhibition assays may serve as better surrogates of clinical efficacy than the assays currently used for the assessment of candidate TB vaccines.

The devR-devS two-component system of Mycobacterium tuberculosis was identified earlier and partially characterized in our laboratory. A devR: :kan mutant of M. tuberculosis was constructed by allelic exchange. The devR mutant strain showed reduced cell-tocell adherence in comparison to the parental strain in laboratory culture media. This phenotype was reversed on complementation with a wild-type copy of devR. The devR mutant and parental strains grew at equivalent rates within human monocytes either in the absence or in the presence of lymphocytic cells. The expression of DevR was not modulated upon entry of M. tuberculosis into human monocytes. However, guinea pigs infected with the mutant strain showed a significant decrease in gross lesions in lung, liver and spleen ; only mild pathological changes in liver and lung; and a nearly 3 log lower bacterial burden in spleen compared to guinea pigs infected with the parental strain. Our results suggest that DevR is required for virulence in guinea pigs but is not essential for entry, survival and multiplication of M. tuberculosis within human monocytes in vitro. The attenuation in virulence of the devR mutant in guinea pigs together with DevR-DevS being a bona fide signal transduction system indicates that DevR plays a critical and regulatory role in the adaptation and survival of M. tuberculosis within tissues.

Tuberculosis (TB) vaccine development is hindered by the lack of clear surrogate markers of protective human immunity to Mycobacterium tuberculosis. This study evaluated the hypothesis that immune-mediated inhibition of mycobacterial growth would more directly correlate with protective TB immunity than other immunologic responses. Bacille Calmette-Guérin (BCG) vaccination, known to induce partial protection against TB, was used as a model system to investigate mechanistic relationships among different parameters of antigen-specific immunity. Effects of primary and booster intradermal BCG vaccinations were assessed in 3 distinct assays of mycobacterial inhibition. Correlations between vaccine-induced growth inhibition and other immune responses were analyzed. BCG significantly enhanced all antigen-specific responses. Peak responses occurred at 2 months after boosting. Statistical analyses suggested that each assay measured unique aspects of mycobacterial immunity. Despite previous evidence that type 1 immune responses are essential for TB immunity, interferon-gamma production did not correlate with mycobacterial inhibition. These results have important implications for TB vaccine development.

Despite the continued importance of tuberculosis as a world-wide threat to public health, little is known about the mechanisms used by human lymphocytes to contain and kill the intracellular pathogen Mycobacterium tuberculosis. We previously described an in vitro model of infection of human monocytes (MN) with virulent M. tuberculosis strain H37Rv in which the ability of peripheral blood lymphocytes to limit intracellular growth of the organism could be measured. In the current study, we determined that lymphocyte-

The mechanisms behind the loss of epithelial barrier function leading to alveolar flooding in acute lung injury (ALI) are incompletely understood. We hypothesized that the tyrosine kinase receptor human epidermal growth factor receptor-2 (HER2) would be activated in an inflammatory setting and participate in ALI. Interleukin-1␤ (IL-1␤) exposure resulted in HER2 activation in human epithelial cells and markedly increased conductance across a monolayer of airway epithelial cells. Upon HER2 blockade, conductance changes were significantly decreased. Mechanistic studies revealed that HER2 trans-activation by IL-1␤ required a disintegrin and metalloprotease 17 (ADAM17)-dependent shedding of the ligand neuregulin-1 (NRG-1). In murine models of ALI, NRG-1-HER2 signaling was activated, and ADAM17 blockade resulted in decreased NRG-1 shedding, HER2 activation, and lung injury in vivo. Finally, NRG-1 was detectable and elevated in pulmonary edema fluid from patients with ALI. These results suggest that the ADAM17-NRG-1-HER2 axis modulates the alveolar epithelial barrier and contributes to the pathophysiology of ALI. Acute lung injury (ALI)3 is a severe clinical disorder with an annual incidence of ϳ200,000 and a mortality of 40% in the United States (1). Most commonly seen in the setting of sepsis (2-4), ALI is marked by disruption of the alveolar barrier, leukocyte activation, release of inflammatory cytokines, and hypercoagulability. The net effect is an increase in alveolar epithelial permeability, resulting in alveolar flooding with proteinrich edema and life-threatening hypoxemia (5). An intact epithelial barrier is essential to maintaining normal pulmonary fluid balance. Indeed, damage to the endothelium alone is insufficient to cause pulmonary edema, whereas epithelial injury results in severe lung injury (6 -8). The epithelium provides a greater resistance to proteins and fluid than the capillary endothelium and is responsible for the active ion transport-dependent removal of edema fluid from the distal air spaces of the lung (9 -11).The tyrosine kinase receptor human epidermal growth factor receptor-2 (HER2) is expressed by pulmonary bronchial epithelial cells and is involved in multiple physiologic processes, including cell proliferation and wound repair. The HER receptor family consists of four type 1, membrane-bound tyrosine kinase receptors: HER1 or epidermal growth factor receptor (EGFR), HER2, HER3, and HER4 (12). HER2 has no known ligand and requires partnering with another HER family member for activation. HER2 and 3 are highly expressed in pulmonary bronchial epithelial cells (compared with HER1 and 4) (13). HER3 is the receptor for the ligand neuregulin-1 (NRG-1), but HER3 has no intrinsic signaling properties (14). Upon NRG-1 binding, HER3 heterodimerizes with HER2, resulting in activation of the HER2 tyrosine kinase domain, HER2 autophosphorylation, and initiation of downstream intracellular signaling cascades (13). NRG-1 is expressed in bronchial epithelial cells (13,15,16) and is shed from the cell ...