A semi-empirical method for prediction of antigenic determinants on protein antigens

AbstractAnalysis of data from experimentally determined antigenic sites on proteins has revealed that the hydrophobic residues Cys, Leu and Val, if they occur on the surface of a protein, are more likely to be a part of antigenic sites. A semi-empirical method which makes use of physicochemical properties of amino acid residues and their frequencies of occurrence in experimentally known segmental epitopes was developed to predict antigenic determinants on proteins. Application of this method to a large number of proteins has shown that our method can predict antigenic determinants with about 75% accuracy which is better than most of the known methods. This method is based on a single parameter and thus very simple to use

High Fidelity Processing and Activation of the Human α-Defensin HNP1 Precursor by Neutrophil Elastase and Proteinase 3

The azurophilic granules of human neutrophils contain four α-defensins called human neutrophil peptides (HNPs 1–4). HNPs are tridisulfide-linked antimicrobial peptides involved in the intracellular killing of organisms phagocytosed by neutrophils. The peptides are produced as inactive precursors (proHNPs) which are processed to active microbicides by as yet unidentified convertases. ProHNP1 was expressed in E. coli and the affinity-purified propeptide isolated as two species, one containing mature HNP1 sequence with native disulfide linkages (“folded proHNP1”) and the other containing non-native disulfide linked proHNP1 conformers (misfolded proHNP1). Native HNP1, liberated by CNBr treatment of folded proHNP1, was microbicidal against Staphylococcus aureus, but the peptide derived from misfolded proHNP1 was inactive. We hypothesized that neutrophil elastase (NE), proteinase 3 (PR3) or cathepsin G (CG), serine proteases that co-localize with HNPs in azurophil granules, are proHNP1 activating convertases. Folded proHNP1 was converted to mature HNP1 by both NE and PR3, but CG generated an HNP1 variant with an N-terminal dipeptide extension. NE and PR3 cleaved folded proHNP1 to produce a peptide indistinguishable from native HNP1 purified from neutrophils, and the microbicidal activities of in vitro derived and natural HNP1 peptides were equivalent. In contrast, misfolded proHNP1 conformers were degraded extensively under the same conditions. Thus, NE and PR3 possess proHNP1 convertase activity that requires the presence of the native HNP1 disulfide motif for high fidelity activation of the precursor in vitro

The impact of cisplat based chemotherapy on advanced ovarian cancer.

Cisplatinum based chemotherapy has become the standard treatment for ovarian cancers due to its proved superiority over non-cisplat based regimes. However, the therapeutic impact of cisplat based regimes compared to cheaper non-cisplatinum based regimes is questionable when multiple variables such as residual disease, histologic type, grade are introduced. This report is a study of 110 Stage III ovarian cancer patients from 1985-89, with cisplat (n = 69) and non cisplat (n = 41) based chemotherapy. The results of both regimes with reference to the multiple variable factors are presented. We conclude that cisplat based regimes appear to be superior to non-cisplat based regimes except probably in poorly differentiated ovarian tumors where the results were similar with either regimen

High fidelity processing and activation of the human α-defensin HNP1 precursor by neutrophil elastase and proteinase 3.

The azurophilic granules of human neutrophils contain four α-defensins called human neutrophil peptides (HNPs 1-4). HNPs are tridisulfide-linked antimicrobial peptides involved in the intracellular killing of organisms phagocytosed by neutrophils. The peptides are produced as inactive precursors (proHNPs) which are processed to active microbicides by as yet unidentified convertases. ProHNP1 was expressed in E. coli and the affinity-purified propeptide isolated as two species, one containing mature HNP1 sequence with native disulfide linkages ("folded proHNP1") and the other containing non-native disulfide linked proHNP1 conformers (misfolded proHNP1). Native HNP1, liberated by CNBr treatment of folded proHNP1, was microbicidal against Staphylococcus aureus, but the peptide derived from misfolded proHNP1 was inactive. We hypothesized that neutrophil elastase (NE), proteinase 3 (PR3) or cathepsin G (CG), serine proteases that co-localize with HNPs in azurophil granules, are proHNP1 activating convertases. Folded proHNP1 was converted to mature HNP1 by both NE and PR3, but CG generated an HNP1 variant with an N-terminal dipeptide extension. NE and PR3 cleaved folded proHNP1 to produce a peptide indistinguishable from native HNP1 purified from neutrophils, and the microbicidal activities of in vitro derived and natural HNP1 peptides were equivalent. In contrast, misfolded proHNP1 conformers were degraded extensively under the same conditions. Thus, NE and PR3 possess proHNP1 convertase activity that requires the presence of the native HNP1 disulfide motif for high fidelity activation of the precursor in vitro

HNP1 forms released by CNBr cleavage of His₆-proHNP1.

<p>HNP1 peptides were generated by CNBr cleavage of folded His₆-proHNP1A and misfolded His₆-proHNP1B. <b>A</b>) HNP1 generated by CNBr cleavage of His₆-proHNP1B (upper tracing) and His₆-proHNP1A (lower tracing) were resolved by C18 RP-HPLC. Bar indicates fractions containing peptides with molecular weight consistent with that of folded/oxidized HNP1 and peaks marked with arrows were further purified by HPLC. <b>B</b>) MALDI-TOF MS of CNBr-cleaved HNP1 derived from His₆-proHNP1B (upper panel) and His₆-proHNP1A (lower panel). <b>C</b>) Analytical C18 RP-HPLC using the Alliance system of HNP1 generated by CNBr-cleavage of His₆-proHNP1B and His₆-proHNP1A compared with neutrophil derived native HNP1. <b>D</b>) AU-PAGE analysis followed by Coomassie staining of 2 µg of each sample shown in panel C: peak B-derived HNP1 (lane 1), peak A-derived HNP1 (lane 2), native HNP1 (lane 3).</p