Immune recognition of a molecule naturally presented as a monomeric or an oligomeric structure: the model of the human chorionic gonadotropin alpha subunit.

The immune recognition of a molecule naturally presented as a monomeric or an oligomeric structure is analyzed using the human chorionic gonadotropin alpha subunit (hCG-alpha) as a model. Indeed, hCG-alpha circulates as either a free subunit or combined to the beta subunit (hCG-beta) to form the dimeric hCG hormone. A T cell study was performed in BALB/c (H-2d) mice which were found to be high responders to hCG-alpha. Mice were immunized with the free hCG-alpha or the dimeric hCG alpha/beta, and their lymph node cells were challenged in vitro with either alpha subunits from different species, hCG or peptides spanning the entire primary structure of hCG-alpha. Proliferation and IL-2 assays demonstrated that hCG-alpha-primed lymph node cells responded equally well to hCG-alpha and hCG alpha/beta, suggesting that both the free and combined hCG-alpha subunits are processed in a similar way. Among the various synthetic peptides used, only those mimicking the hCG-alpha(59-92) C-terminus portion were able to stimulate hCG-alpha-primed lymph node cells, demonstrating that this region contains immunodominant T cell recognition site(s). The hCG-alpha(23-43) and (32-59) peptides, although incapable of stimulating T cells primed with hCG-alpha, elicited a T cell response when used as immunogens. These regions encompassed cryptic epitopes which were not generated during hCG-alpha processing in H-2d mice. The T cell epitopes of hCG-alpha above described as immunodominant or cryptic on the free alpha subunit, had similar characteristics when the alpha/beta dimer was used as the immunogen. In contrast, T cells primed with peptides mimicking immunodominant sites recognized differently the hCG-alpha and the hCG alpha/beta antigens. Moreover, the analysis of the B cell response to all the immunogenic hCG-alpha peptides indicated that they bear B and T cell epitopes as well. Antibodies elicited against the hCG-alpha(59-92) or (32-59) peptide were capable of recognizing the alpha subunit in its free form but not in the alpha/beta hCG dimer. Such study deserves attention for the comprehensive mechanisms of the immune response to hCG as well as for the design of anti-hCG vaccines.     

Activity of Bisnaphthalimidopropyl Derivatives against Trypanosoma brucei

Current treatments for African trypanosomiasis are either toxic, costly, difficult to administer, or prone to elicit resistance. This study evaluated the activity of bisnaphthalimidopropyl (BNIP) derivatives against Trypanosoma brucei. BNIPDiaminobutane (BNIPDabut), the most active of these compounds, showed in vitro inhibition in the single-unit nanomolar range, similar to the activity in the reference drug pentamidine, and presented low toxicity and adequate metabolic stability. Additionally, using a murine model of acute infection and live imaging, a significant decrease in parasite load in BNIPDabut-treated mice was observed. However, cure was not achieved. BNIPDabut constitutes a new scaffold for antitrypanosomal drugs that deserves further consideration.     

CHROMagar mSuperCARBA and RAPIDEC® Carba NP test for detection of carbapenemase-producing Enterobacteriaceae

A novel chromogenic medium CHROMagar mSuperCARBA was evaluated to detect carbapenem-resistant Gram-negatives. This medium is as sensitive and as specific as the SUPERCARBA medium for detecting KPC, MBL and OXA-48-type producers (100% and 100%, respectively) and is compatible with subsequent testing of carbapenemase activity using the RAPIDEC^® CARBA NP.     

Breast Density Analysis Using an Automatic Density Segmentation Algorithm

Breast density is a strong risk factor for breast cancer. In this paper, we present an automated approach for breast density segmentation in mammographic images based on a supervised pixel-based classification and using textural and morphological features. The objective of the paper is not only to show the feasibility of an automatic algorithm for breast density segmentation but also to prove its potential application to the study of breast density evolution in longitudinal studies. The database used here contains three complete screening examinations, acquired 2 years apart, of 130 different patients. The approach was validated by comparing manual expert annotations with automatically obtained estimations. Transversal analysis of the breast density analysis of craniocaudal (CC) and mediolateral oblique (MLO) views of both breasts acquired in the same study showed a correlation coefficient of ρ = 0.96 between the mammographic density percentage for left and right breasts, whereas a comparison of both mammographic views showed a correlation of ρ = 0.95. A longitudinal study of breast density confirmed the trend that dense tissue percentage decreases over time, although we noticed that the decrease in the ratio depends on the initial amount of breast density.     

A monoclonal antibody against a synthetic peptide is specific for the free native human chorionic gonadotropin beta-subunit

A totally synthetic molecule (109-145 peptide) analogous to the beta-subunit carboxyl terminus was used as an antigen in the development of antibodies by the hybridoma technique. A monoclonal antibody (702 D7) specifically recognized the free native beta-human CG (beta hCG). 702 D7 was of the immunoglobulin G1 subclass and was directed against an antigenic site localized in a 10-amino acid sequence (109-118) or less. The recognition of an epitope located in the 109-118 region could explain the specific recognition of beta hCG observed with 702 D7, in contrast to monoclonal antibodies directed against a 118-145 region with a recognition of both beta hCG and whole hCG, as observed with a second monoclonal antibody (1032) to synthetic peptide. Immunohistochemical results and preliminary data obtained from the immunoradiometric assay show that 702 D7 provides a clinical tool for the detection of free beta-subunit secretion even at low concentrations, and could allow the study of this subunit or its metabolites produced by normal and tumoral cells.     

Effects of chronic noradrenaline on the nitric oxide pathway in human endothelial cells

Altered endothelium-dependent vasodilation has been observed in congestive heart failure (CHF), a disease characterized by a sustained adrenergic activation. The purpose of our study was to test the hypothesis that chronically elevated catecholamines influence the nitric oxide (NO) pathway in the human endothelium. Human umbilical vein endothelial cells (HUVEC) were exposed for 7 days to a concentration of noradrenaline (NA, 1 ng/mL) similar to that found in the blood of patients with CHF. Kinetics of endothelial constitutive NO synthase (ecNOS) and inducible NO synthase (iNOS) activity, measured by [³H]L-arginine to [³H]L-citrulline conversion, and protein expression of ecNOS and iNOS, assessed by Western blot analysis, were unaffected by chronic NA treatment. Furthermore, no changes in subcellular fraction-associated ecNOS were found; this indirectly shows that chronic NA did not cause phosphorylation of the enzyme. Moreover, [³H]L-arginine transport through the plasma membrane was conserved in chronically NA-treated cells. The data demonstrate that prolonged in vitro exposure to pathologic CHF-like NA does not affect the L-arginine NO pathway in human endothelial cells. Received: 11 July 1997, Returned for revision: 13 August 1997, Revision received: 6 October 1997, Returned for 2. revision: 17 November 1997, 2. Revision received: 5 January 1998, Accepted: 26 January 1998