Use of an antigen-capture assay for characterisation of monoclonal antibodies to mycobacterial lipoarabinomannan

Monoclonal antibodies directed to six separate antigen molecules of Mycobacterium leprae have been tested in an antigen-capture assay based on combined use of polyclonal ("capture") and monoclonal ("detector") antibody reagents. This approach provides a potentially versatile, sensitive and specific assay for detection and relative quantitation of M. leprae antigens. Characterisation of monoclonal antibodies to mycobacterial lipoarabinomannan (LAM-B) by the antigen-capture assay indicates that some of the antigenic determinants present on LAM-B from M. leprae may be either absent altogether or present at much lower concentrations on the corresponding LAM-B structure form M. tuberculosis.     

Genetic and immunohistochemical analysis of pancreatic acinar cell carcinoma: frequent allelic loss on chromosome 11p and alterations in the APC/beta-catenin pathway

Acinar cell carcinomas (ACCs) are rare malignant tumors of the exocrine pancreas. The specific molecular alterations that characterize ACCs have not yet been elucidated. ACCs are morphologically and genetically distinct from the more common pancreatic ductal adenocarcinomas. Instead, the morphological, immunohistochemical, and clinical features of ACCs overlap with those of another rare pancreatic neoplasm, pancreatoblastoma. We have recently demonstrated a high frequency of allelic loss on chromosome arm 11p and mutations in the APC/beta-catenin pathway in pancreatoblastomas, suggesting that similar alterations might also play a role in the pathogenesis of some ACCs. We analyzed a series of 21 ACCs for somatic alterations in the APC/beta-catenin pathway and for allelic loss on chromosome 11p. In addition, we evaluated the ACCs for alterations in p53 and Dpc4 expression using immunohistochemistry, and for microsatellite instability (MSI) using polymerase chain amplification of a panel of microsatellite markers. Allelic loss on chromosome 11p was the most common genetic alteration in ACCs, present in 50% (6 of 12 informative cases). Molecular alterations in the APC/beta-catenin pathway were detected in 23.5% (4 of 17) of the carcinomas, including one ACC with an activating mutation of the beta-catenin oncogene and three ACCs with truncating APC mutations. One ACC (1 of 13, 7.6%) showed allelic shifts in four of the five markers tested (MSI-high), two (15.4%) showed an allelic shift in only one of the five markers tested (MSI-low), and no shifts were detected in the remaining 10 cases. The MSI-high ACC showed medullary histological features. In contrast, no loss of Dpc4 protein expression or p53 accumulation was detected. These results indicate that ACCs are genetically distinct from pancreatic ductal adenocarcinomas, but some cases contain genetic alterations common to histologically similar pancreatoblastomas.     

Chemical synthesis and serology of disaccharides and trisaccharides of phenolic glycolipid antigens from the leprosy bacillus and preparation of a disaccharide protein conjugate for serodiagnosis of leprosy.

We examined the structural requirements within the species-specific 3,6-di-O-methyl-beta-D-glucopyranosyl-(1 leads to 4)-2,3-di-O-methyl- alpha-L-rhamnopyranosyl-(1 leads to 2)-3-O-methyl-alpha-L-rhamnopyranose unit of the phenolic glycolipid I antigen of Mycobacterium leprae for binding to anti-glycolipid immunoglobulin M from human leprosy sera. We used chemically defined, partially deglycosylated fragments of phenolic glycolipid I, two other minor M. leprae-specific phenolic glycolipids (those containing 6-O-methyl-beta-D-glucopyranosyl-(1 leads to 4)-2,3-di-O-methyl-alpha- L-rhamnopyranosyl-(1 leads to 2)-3-O-methyl-alpha-L-rhamnopyranose and 3,6-di-O-methyl-beta-D-glucopyranosyl-(1 leads to 4)-3-O-methyl-alpha- L-rhamnopyranosyl-(1 leads to 2)-3-O-methyl-alpha-rhamnopyranose units), and phenolic glycolipids from other mycobacteria. Additionally, the trisaccharide of phenolic glycolipid I, the 3,6-di-O-methyl-beta-D-glucopyranosyl-(1 leads to 4)-2, 3-di-O-methyl-alpha-L-rhamnopyranose, the 6-O-methyl-beta-D-glucopyranosyl-(1 leads to 4)-2,3-di-O-methyl-alpha- L-rhamnopyranose, and the beta-D-glucopyranosyl-(1 leads to 4)-2,3-di-O-methyl-alpha- L-rhamnopyranose disaccharides were synthesized and characterized, and their activities were examined. Only the phenolic glycolipids containing 3,6-di-O-methyl-beta-D-glucopyranosyl at the nonreducing terminus were efficient in binding the anti-glycolipid immunoglobulin M, and the 3,6-di-O-methyl-beta-D-glucopyranosyl-containing di- and trisaccharides were the most effective in inhibiting this binding. Thus, the 3,6-di-O-methyl-beta-D-glucopyranosyl substituent was recognized as the primary antigen determinant in phenolic glycolipid I. With this information, bovine serum albumin containing reductively aminated 3,6-di-O-methyl-beta-D-glucopyranosyl-(1 leads to 4)-2,3-di-O-methyl- L-rhamnose was prepared and shown to be highly active in the serodiagnosis of leprosy.     

Mutation of antitrypsin to antithrombin. alpha 1-antitrypsin Pittsburgh (358 Met leads to Arg), a fatal bleeding disorder

Our previous studies predicted a functional relationship between the plasma proteins alpha 1-antitrypsin and antithrombin III. To elucidate this relationship we investigated the plasma of a 14-year-old boy who had died from an episodic bleeding disorder. A variant alpha 1-antitrypsin was identified in which the methionine at position 358 had been replaced by an arginine. This had converted the alpha 1-antitrypsin from its normal function as an inhibitor of elastase to that of an inhibitor of thrombin. This finding indicates that the reactive center of alpha 1-antitrypsin is methionine 358, which acts as a bait for elastase, just as the normal reactive center of antithrombin III is arginine 393, which acts as a bait for thrombin. The independence of the new thrombin inhibitor from heparin control explains the bleeding disorder; it also indicates that heparin normally acts directly on antithrombin III, revealing its inherent inhibitory activity. The episodic nature of the bleeding was a consequence of the mutant protein's being an acute-phase reactant, the level of which increased several-fold after trauma.     

Classification and subtype prediction of adult soft tissue sarcoma by functional genomics

Adult soft tissue sarcomas are a heterogeneous group of tumors, including well-described subtypes by histological and genotypic criteria, and pleomorphic tumors typically characterized by non-recurrent genetic aberrations and karyotypic heterogeneity. The latter pose a diagnostic challenge, even to experienced pathologists. We proposed that gene expression profiling in soft tissue sarcoma would identify a genomic-based classification scheme that is useful in diagnosis. RNA samples from 51 pathologically confirmed cases, representing nine different histological subtypes of adult soft tissue sarcoma, were examined using the Affymetrix U95A GeneChip. Statistical tests were performed on experimental groups identified by cluster analysis, to find discriminating genes that could subsequently be applied in a support vector machine algorithm. Synovial sarcomas, round-cell/myxoid liposarcomas, clear-cell sarcomas and gastrointestinal stromal tumors displayed remarkably distinct and homogenous gene expression profiles. Pleomorphic tumors were heterogeneous. Notably, a subset of malignant fibrous histiocytomas, a controversialhistological subtype, was identified as a distinct genomic group. The support vector machine algorithm supported a genomic basis for diagnosis, with both high sensitivity and specificity. In conclusion, we showed gene expression profiling to be useful in classification and diagnosis, providing insights into pathogenesis and pointing to potential new therapeutic targets of soft tissue sarcoma.     

Immunoglobulin G, A, and M Responses in Serum and Circulating Immune Complexes Elicited by the 16-Kilodalton Antigen of Mycobacterium tuberculosis

The 16-kDa cytosolic antigen of M. tuberculosis was purified to homogeneity by molecular sieving chromatography, and the diagnostic potential of the antigen was evaluated in various categories of patients by enzyme-linked immunosorbent assay (ELISA). The immunoglobulin G (IgG), IgA, and IgM antibody levels to 16-kDa antigen were estimated in the two polar groups, namely, smear- and culture-positive pulmonary tuberculosis (S⁺C⁺) patients and healthy subjects (HS). Sensitivities of 62, 52 and 11% with specificities of 100, 97, and 95% were obtained for the three isotypes, respectively. The total number of positives by a combination of the three isotypes was analyzed in the polar groups, and the sensitivity improved to 83% with a specificity of 93%. Even when a combination of IgG and IgA alone was considered, the sensitivity was 82% with a specificity of 97%. Polyethylene glycol precipitation of the circulating immune complex (CIC) in sera was carried out. The CIC-bound antibodies to 16-kDa antigen were assessed by ELISA in the S⁺C⁺, S⁻C⁺, and S⁻C⁻ categories of patients. Measuring the IgG-IgA-IgM combination positivities of the CIC-bound antibodies gave sensitivities of 97.5, 100, and 45.3%, respectively. The specificity of the assay with these combinations was maintained at 95.4%.     

Prion protein accumulation and neuroprotection in hypoxic brain damage

The function of the normal conformational isoform of prion protein, PrP(C), remains unclear although lines of research have suggested a role in the cellular response to oxidative stress. Here we investigate the expression of PrP(C) in hypoxic brain tissues to examine whether PrP(C) is in part regulated by neuronal stress. Cases of adult cerebral ischemia and perinatal hypoxic-ischemic injury in humans were compared with control tissues. PrP(C) immunoreactivity accumulates within neuronal processes in the penumbra of hypoxic damage in adult brain, and within neuronal soma in cases of perinatal hypoxic-ischemic injury, and in situ hybridization analysis suggests an up-regulation of PrP mRNA during hypoxia. Rodents also showed an accumulation of PrP(C) in neuronal soma within the penumbra of ischemic lesions. Furthermore, the infarct size in PrP-null mice was significantly greater than in the wild type, supporting the proposed role for PrP(C) in the neuroprotective adaptive cellular response to hypoxic injury.     

Serum cholesterol levels and stressor controllability in rats

Whether an organism can control a stressful event is often an important variable determining the impact of the event on physiology and behavior. Numerous behavioral and physiological variables are more adversely affected by uncontrollable stress. The present experiment with rat subjects compared the effect of controllable stress (escape conditioning) or uncontrollable stress (yoked control group) vs. home cage controls on total cholesterol, as well as high-density lipoprotein (HDL) and low/very-low density lipoprotein (LDL/VLDL) serum cholesterol. Results indicated that both stressed groups had higher total and LDL/VLDL cholesterol levels than home cage controls. No group differences were observed with HDL cholesterol. The escape and yoked control subjects did not differ from each other in any dependent measure. Results are discussed in terms of the probable mediators of stress-induced cholesterol increases, and the fact that these mediators may be insensitive to stressor controllability.     

Serological specificity of phenolic glycolipid I from Mycobacterium leprae and use in serodiagnosis of leprosy

The serological activities of the specific phenolic glycolipid I from Mycobacterium leprae, its dissected parts, and related glycolipids from other mycobacteria were examined by enzyme-linked immunosorbent assay against hyperimmune anti-M. leprae rabbit antiserum and sera from patients with leprosy and other mycobacterial diseases. High anti-phenolic glycolipid I immunoglobulin M antibodies were found in 23 of 24 (96%) of lepromatous leprosy patients on short term chemotherapy and in 8 of 13 tuberculoid leprosy patients (62%). Sera from patients with tuberculosis or atypical mycobacterial infections were devoid of anti-phenolic glycolipid I activity. The structurally related phenolic glycolipids from Mycobacterium kansasii and Mycobacterium bovis and the aglycone segments of the M. leprae product showed no significant activity. Thus, the trisaccharide determinant of phenolic glycolipid I is specific in its structure, serological activity, and, to a lesser extent, the antibody class it evokes.