Colonial dissociation and susceptibility to phagocytosis of Pseudomonas aeruginosa grown in a chamber implant model in mice.

Pseudomonas aeruginosa strains were grown in 1-cm plastic chambers sealed at both ends with porous Millipore filters and implanted in the peritonea of mice. Mucoid and nonmucoid strains of P. aeruginosa isolated from a patient with cystic fibrosis largely retained their phenotypes when grown for up to 1 year in this in vivo system, although colonial dissociation occurred, as observed in chronic lung infections of patients with cystic fibrosis. In the absence of added opsonins, P. aeruginosa M2 cells taken directly from the in vivo system were significantly more susceptible to phagocytosis than were the same P. aeruginosa cells after being washed in buffer. Phagocytosis of in vivo-grown P. aeruginosa cells could be further enhanced by using a porin protein F-specific monoclonal antibody.     

Are three sputum acid-fast bacillus smears necessary for discontinuing tuberculosis isolation?

To evaluate the efficacy of three sputum acid-fast bacillus (AFB) smears to rule out pulmonary tuberculosis, sputum AFB smear and culture results were analyzed at two university-affiliated teaching hospitals. The negative predictive value of the smear increased by only 0.2% on days 2 and 3 each, indicating that in low-prevalence populations, there is limited value in requiring three negative sputum AFB smears before discontinuing tuberculosis isolation.     

Elevated abeta42 in skeletal muscle of Alzheimer disease patients suggests peripheral alterations of AbetaPP metabolism

The levels of amyloid-beta40 (Abeta40) and Abeta42 peptides were quantified in temporalis muscles and brain of neuropathologically diagnosed Alzheimer disease (AD) and of nondemented individuals. This was achieved by using a novel analytical approach consisting of a combination of fast-performance liquid chromatographic (FPLC) size exclusion chromatography developed under denaturing conditions and europium immunoassay on the 4.0- to 4.5-kd fractions. In the temporalis muscles of the AD and nondemented control groups, the average values for Abeta42 were 15.7 ng/g and 10.2 ng/g (P = 0.010), and for Abeta40 they were 37.8 ng/g and 29.8 ng/g (P = 0.067), respectively. Multiple regression analyses of the AD and control combined populations indicated that 1) muscle Abeta40 and muscle Abeta42 levels were correlated with each other (P < 0.001), 2) muscle Abeta40 levels were positively correlated with age (P = 0. 036), and 3) muscle Abeta42 levels were positively correlated with Braak stage (P = 0.042). Other forms of the Abeta peptide were discovered by mass spectrometry, revealing the presence of Abeta starting at residues 1, 6, 7, 9, 10, and 11 and ending at residues 40, 42, 44, 45, and 46. It is possible that in AD the skeletal muscle may contribute to the elevated plasma pool of Abeta and thus indirectly to the amyloid deposits of the brain parenchyma and cerebral blood vessels. The increased levels of Abeta in the temporalis muscles of AD patients suggest that alterations in AbetaPP and Abeta metabolism may be manifested in peripheral tissues.     

Human Mannose-Binding Protein Inhibits Infection of HeLa Cells by Chlamydia trachomatis

The role that collectin (mannose-binding protein) may play in the host’s defense against chlamydial infection was investigated. Recombinant human mannose-binding protein was used in the inhibition of cell culture infection by Chlamydia trachomatis (C/TW-3/OT, E/UW-5/Cx, and L₂/434/Bu), Chlamydia pneumoniae (AR-39), and Chlamydia psittaci (6BC). Mannose-binding protein (MBP) inhibited infection of all chlamydial strains by at least 50% at 0.098 μg/ml for TW-3 and UW-5, and at 6.25 μg/ml for 434, AR-39, and 6BC. The ability of MBP to inhibit infection with strain L₂ was not affected by supplementation with complement or addition of an L₂-specific neutralizing monoclonal antibody. Enzyme-linked immunosorbent assay and dot blot analyses showed MBP bound to the surface of the organism to exert inhibition, which appeared to block the attachment of radiolabeled organisms to HeLa cells. Immunoblotting and affinity chromatography indicated that MBP binds to the 40-kDa glycoprotein (the major outer membrane protein) on the outer surface of the chlamydial elementary body. Hapten inhibition assays with monosaccharides and defined oligosaccharides showed that the inhibitory effects of MBP were abrogated by mannose or high-mannose type oligomannose-oligosaccharide. The latter carbohydrate is the ligand of the 40-kDa glycoprotein of C. trachomatis L₂, which is known to mediate attachment, suggesting that the MBP binds to high mannose moieties on the surface of chlamydial organisms. These results suggest that MBP plays a role in first-line host defense against chlamydial infection in humans.     

Systemic Chlamydia trachomatis infection in mice: a comparison of lymphogranuloma venereum and trachoma biovars.

We developed a murine model of systemic infection with Chlamydia trachomatis biovar lymphogranuloma venereum (LGV). The pathological features of this infection resemble those of human LGV infection since both are characterized by granuloma formation. Mice developed resistance to reinfection with LGV, and this resistance was based on cellular immune mechanisms since it was transferable with immune spleen cells but not with immune serum. Resistance required viable organisms for induction. We compared LGV biovar infection with trachoma biovar infection. Trachoma biovar produced similar but less marked microbiological and pathological features. Cross-immunity was less apparent between serovars from trachoma and LGV biovars than it was between serovars within the same biovar. This model of systemic C. trachomatis infection will be useful in exploring virulence features of LGV.     

Cytokine responses during mycobacterial and schistosomal antigen-induced pulmonary granuloma formation. Production of Th1 and Th2 cytokines and relative contribution of tumor necrosis factor.

Synchronized pulmonary granulomas (GRs) were induced in presensitized mice by intravenous embolization of polymer beads bound with purified protein derivative (PPD) of Mycobacteria tuberculosis or soluble antigens derived from Schistosoma mansoni eggs (SEA). Uncoated beads served as a foreign body control (CON). Antigen-coated beads elicited GRs with characteristic epithelioid macrophages and multinucleate giant cells by 4 days after embolization. Unlike PPD GR, SEA bead lesions contained eosinophils, whereas CON beads elicited only a limited mononuclear infiltrate. GRs and draining lymph nodes (LN) were assessed on days 2, 4, and 8 for Th1-(interleukin-2 [IL-2], interferon-gamma[IFN] and Th2-type (IL-4, IL-5, and IL-10) cytokines. CON GR produced only a small amount of IFN-gamma on day 2 and failed to induce a significant response in draining LN. In contrast, both PPD and SEA antigen-coated beads induced reactive lymphoid hyperplasia but differed greatly in local and regional cytokine profiles. PPD GR produced IFN-gamma on day 2 and the draining LN produced predominantly Th1 cytokines on days 2 and 4. In contrast, SEA beads GRs were dominated by Th2 cytokines. The corresponding LN produced IL-2 and IL-4 on day 2; IL-2, IL-4, IFN-gamma, and IL-10 on day 4; then IL-2, IFN-gamma, and IL-4 on day 8, probably reflecting maturational changes of T cells. Macrophages (MP) from bead GR also showed different patterns of IL-6 and tumor necrosis factor (TNF) production. Compared with CON GR, MPs from PPD GR were weak sources of IL-6, whereas those of SEA GR showed enhanced and accelerated production. In contrast, MP of PPD GR had augmented TNF-producing capacity, whereas those of SEA GR showed delayed TNF production. In vivo depletion of TNF, respectively, caused 40 and 10% decreases in PPD GR and SEA GR but had no effect on CON GR area, indicating that TNF contributed to a greater degree to the PPD response. These data show that depending on the inciting agent, GR can be mediated by different cytokines. Characterization of inflammatory lesions by cytokine profiles should allow design of more rational therapeutic interventions.     

Effect of Chlamydia pneumoniae on cellular ATP content in mouse macrophages: role of Toll-like receptor 2

Chlamydiae are obligate intracellular gram-negative bacteria and are dependent on the host cell for ATP. Thus, chlamydial infection may alter the intracellular levels of ATP and affect all energy-dependent processes within the cell. We have shown that both live C. pneumoniae and inactivated C. pneumoniae induce markers of cell death prior to completion of the bacterial growth cycle. As depletion of ATP could account for the observed increase in cell death, the effects of C. pneumoniae on ATP concentrations within mouse macrophages were investigated. Live, heat-killed, and UV-inactivated C. pneumoniae cultures (at multiplicities of infection [MOIs] of 0.01, 0.1, and 1.0) were incubated with mouse bone marrow macrophages isolated from C57BL/6J mice and mice deficient in Toll-like receptors. Treatment of the macrophages with both live and inactivated C. pneumoniae increased the ATP content of the cells. In cells infected with live C. pneumoniae, the increase was inversely proportional to the MOI. In cells treated with inactivated C. pneumoniae, the increase in ATP content was smaller than that induced by infection with live organisms and was proportional to the MOI. The increase in ATP content early in the developmental cycle was independent of the growth of C. pneumoniae, while sustained induction required live organisms. The capacity of C. pneumoniae to increase the ATP content was ablated in macrophages deficient in expression of either Toll-like receptor 2 or the Toll-like receptor accessory protein MyD88. In contrast, no effect was observed in macrophages lacking expression of Toll-like receptor 4.     

Frequent presence of neuroendocrine small cells in thymic carcinoma: a light microscopic and immunohistochemical study

AIMS: Neuroendocrine differentiation has been described in conventional carcinomas of various organs. Small cells postulated to be neuroendocrine cells were observed previously in some thymic carcinomas. This study was conducted to confirm and characterize the presence of neuroendocrine small cells in thymic carcinomas by light microscopy and immunohistochemistry. METHODS AND RESULTS: Twenty-two thymic carcinomas were studied by light microscopy to detect the presence of small neuroendocrine-like cells. They were found in four of 10 squamous cell carcinomas (SCC) and seven of eight adenosquamous carcinomas (ASC). No small cells were observed in three lymphoepithelioma-like carcinomas (LELC) and one adenocarcinoma. The small cells were located within the tumour nests and constituted less than 1% of the entire tumour. In one case, small cells also extended outside the tumour nests. Rosette formation was seen in three cases. They were proved to be neuroendocrine cells by their immunoreactivity to neuron-specific enolase, chromogranin A, and/or synaptophysin. A few scattered neuroendocrine small cells were found only by immunohistochemistry in one case each of SCC, ASC, and LELC. The small cells were also strongly positive for cytokeratin (CK) 8 and CK18 but negative for CK19 and CK20. The predominant carcinoma cells other than the neuroendocrine small cells also displayed neuroendocrine markers in 68% of the cases studied. CONCLUSIONS: Neuroendocrine small cells can be recognized by light microscopic examination in approximately 61% of thymic SCC and ASC. Neuroendocrine markers, CK8 and CK18 can aid in confirming their presence. The neuroendocrine small cells present in thymic carcinomas are different from the main carcinoma cells displaying immunohistochemical neuroendocrine markers. The presence of neuroendocrine small cells could be an useful marker for the differentiation of thymic carcinomas from thymomas and carcinomas of other sites.