Bioluminescence assay for the highly sensitive detection of botulinum neurotoxin A activity.

This article describes a novel bioluminescence assay for detecting the proteolytic activity of Botulinum NeuroToxins (BoNT) in complex matrices. The assay is capable of detecting traces of BoNT in blood samples as well as in food drinks. The assay was responsive to BoNT/A subtypes 1 to 5, and serotype E3 in buffered solutions. It was responsive to filtered Clostridium botulinum supernatants and BoNT/A1 in complex with neurotoxin associated proteins in bouillon and milk (3.8% fat) down to 400 fM after 4 h RT incubation and in bouillon at concentrations down to 120 fM after 21 h RT incubation. In combination with an immunocapture/enrichment step it could detect BoNT/A1 in citrated plasma at concentrations down to 30 fM (1.2 mouse LD50 per mL). The simplicity of the assay, combined with a demonstrated ability to lyophilize the reagents, demonstrates its usefulness for detection of BoNT in non-specialised analytical laboratories.

Characterization and expression analysis of two human septin genes, PNUTL1 and PNUTL2.

The presence and role of septin proteins in yeast is well documented, but there is a growing appreciation for this family of proteins beyond yeast and extending to human cells. In this report we present the characterization and comparison of two highly similar human septin genes, PNUTL1 and PNUTL2. We compare the exon/intron structure of both genes, the steady-state mRNA levels in tumor cell lines and adult organs, the conceptual translation products from alternatively processed mRNAs and the development of specific immunologic reagents distinguishing either PNUTL1 or PNUTL2. The results illustrate a remarkable similarity between the two genes and their protein products while identifying specific differences in mRNA expression patterns. A summary of the described functional roles for mammalian septins is discussed along with an attempt to assimilate the alternative nomenclature existing for the same human septins, such as references to PNUTL1 and PNUTL2 as hCDCrel-1 and hCDCrel-2, respectively. The characterization of PNUTL1 and PNUTL2 represents a fundamental step in completing the characterization of the entire family of human septin genes.

Biochemical characterization of binding sites for dihydropyridine and omega-conotoxin in brain of adult chicken.

Binding studies using the calcium channel blockers omega-conotoxin and dihydropyridine revealed a rather equal amount of binding sites in brain from adult chicken. The omega-conotoxin binding sites could be solubilized using digitonin, without substantial loss, whereas a great decrease in dihydropyridine binding sites was observed, indicating that both types of binding sites have different sensitivity to solubilization. In contrast to ion exchange chromatography where both binding sites comigrated, glycoprotein affinity chromatography led to a different partition of the binding sites in the flow through and eluate fractions. Our results indicate that both types of calcium channel blockers bind to different targets in adult chicken.

Alterations in gene expression associated with stepwise acquisition of malignancy in murine cytotoxic T cell lines.

We have isolated a series of variant cell lines from a murine CD8+ T cell clone representing distinct stages in stepwise acquisition of malignancy. A first type of variant has acquired independency of restimulation with MHC/Ag but has kept dependence on IL-2 for continuous growth in culture. A second type of variant has acquired, in addition, independency of IL-2. A third type of variant was isolated from tumors induced upon injection of IL-2 independent variants into syngeneic mice. Clonal relatedness between the cell line was ascertained by Southern blot and sequence analyses of their TCR beta chain genes. The cell lines were analyzed for their expression of genes typical for CD8+ T cells, using Northern blot hybridization, flow cytometry, and functional methods. Concentrating on the transition from IL-2 dependent to IL-2 independent cellular growth, we find the same triad of changes in two independently derived groups of variant cell lines: loss of expression of the CD8 alpha gene with concomitant loss of CD8 from the cell surface, a slight but significant overexpression of IL-2R alpha and beta chains with increased low affinity IL-2 binding sites, and constitutive overexpression of c-myc. Autocrine IL-2 dependent growth could be excluded. Expression of p56lck did not vary between the cell lines. We discuss the possibility that IL-2 independent growth may be associated with intracellular redistribution of p56lck from CD8 alpha to IL-2R beta, thus generating constitutively active IL-2R. Ex vivo established tumor variants differed from their parental culture cell lines by their constitutive secretion of IFN-gamma.(ABSTRACT TRUNCATED AT 250 WORDS)

Affinity enhancement and transmembrane signaling are associated with distinct epitopes on the CD8 alpha beta heterodimer.

CD8 is a heterodimeric membrane glycoprotein on MHC class I-restricted T lymphocytes that cooperates with the alpha beta CD3 TCR in the recognition of MHC class I molecules presenting antigenic peptides. Co-operation has two components: enhancement of the affinity of MHC/peptide-TCR interaction, and signal transduction through the T cell membrane. The cytolytic function of CTL is primarily dependent on the affinity-enhancement component of CD8-TCR cooperation whereas activation of resting CD8+ T cells is primarily dependent on transmembrane signaling. Using a panel of mAb, two to the alpha-chain and three to the beta-chain of CD8, we investigated the relationships between epitopes and functional regions of the CD8 molecule. Two of the antibodies, one to the alpha-chain and one to the beta-chain of CD8, inhibit the cytolytic function of CTL but not the generation of CTL from resting T cells. Another two antibodies, also one to the alpha- and one to the beta-chain, inhibited the generation of CTL while enhancing the cytolytic function of CTL. These results suggest that both the alpha- and beta-chain of CD8 possess two distinct regions, one involved in affinity enhancement and the other in transmembrane signaling. The former may be the MHC class I-binding region whereas the latter may associate with the alpha beta CD3 TCR. The data can explain the apparent functional equivalence of CD8 alpha alpha homodimers and alpha beta heterodimers.