Publications

Publications

The Pirbright Institute publication directory contains details of selected publications written by our researchers.

There were a total of 2053 results for your search.

Abstract

We have investigated the role of specific components of the thymic stroma during development of CD4(-)8(-) T cell precursors by separating and reaggregating precursor subsets with individual or combinations of stromal cells. We show that while the development of CD25(+) 44(+) precursors is dependent upon a combination of major histocompatibility complex (MHC) class II+ thymic epithelial cells and fibroblasts, their direct descendants, CD25(+) 44(-) precursors, develop to the CD4(+) 8(+) stage in the presence of MHC class II+ thymic epithelial cells alone. Thus, CD25(+) 44(+) precursors are the last developmental stage to be dependent upon fibroblast support. In addition, while metabolically inactive, 1-ethyl-3-(3'-dimethylaminopropyl)carbodiimide (ECDI)-treated fibroblasts retain the ability to promote T cell development, prior treatment with hyaluronidase abrogates this effect, suggesting that fibroblast-associated extracellular matrix components are the key elements involved. In support of this, we show that fibroblasts are located in cortical regions of the thymus where T cell precursors are known to reside, and that these fibroblasts are associated with an extensive extracellular matrix not found on thymic epithelial cells. Finally, antibodies to alpha 4 integrin and CD44 interfere with the efficiency with which CD4(+) 8(+) cells are generated from CD25(+) 44(+) precursors in reaggregate cultures and also reduce the binding of the latter to 3T3 fibroblasts, suggesting these molecules play a role in bringing T cell precursors into contact with fibroblast-associated extracellular matrix.
Cabrita G, Iqbal M, Reddy H, Kemp G (1997)

Activation of the adenovirus protease requires sequence elements from both ends of the activating peptide

Journal of Biological Chemistry 272 (9), 5635-5639

Abstract

The adenovirus protease requires activation by an 11-residue peptide, GVQSLKRRRCF, to achieve maximum proteolytic activity. Derived from the C terminus of the viral protein pVI, the activating peptide (pVI-CT) forms a disulfide bond with cysteine 104 of the protease and causes a conformational change that accompanies the development of proteolytic activity, Results presented here show that the interaction of pVI-CT with the protease is dependent not only on the cysteine 10 but also on glycine 1 and valine 2, Removal of these residues, acetylation of the N-terminal glycine, or mutation of the valine to alanine or threonine significantly reduces or abolishes activation, Peptides lacking Gly-l and Val-2 still form a disulfide bond with the protease but do not cause a conformational change in the protease also they are not effective inhibitors of activation as the interaction is readily reversed by full-length pVI-CT. These results suggest that pVI-CT causes activation by binding to two distinct regions of the protease and in doing so stabilizes the catalytic site, The reversible nature of the activation, suggested by the results presented here, may well reflect an in vivo regulatory mechanism.

Abstract

We have shown that an antibody (9C10) to the alpha 4 integrin induces apoptosis in murine immature CD4(+) CD8(+) thymocytes and in activated (but not resting) mature lymph node T cells. In both cases, apoptosis is blocked by the highly selective protein kinase C (PKC) inhibitor Ro31.8425, suggesting that 9C10 induces signalling through the alpha 4 integrin resulting in PKC activation leading to apoptosis. Overall, our results indicate the potential role of the alpha 4 integrin-mediated interactions in apoptosis induction during T-cell development and following mature T-cell activation.

Abstract

Adenovirus codes for a protease the activity of which can be regulated in vitro by an 11 residue peptide (GVQSLKRRRCF) derived from another viral protein, pVI. Three cysteine residues, one in the activating peptide and two in the protease (C104 and C122), play a central role in both activation and catalysis. Expression of protease mutants in insect cells has shown that C104 is not essential for proteolytic activity. GVQSLKRRRCF also caused a concentration-dependent increase in tryptophan fluorescence of protease expressed in Escherichia coli that paralleled the increase in proteolytic activity, indicating that activation was accompanied by a conformational change. Tryptophan fluorescence of C104S was not increased by the addition of GVQSLKRRRCF, nor was the fluorescence of wildtype protease increased by the addition of the peptide analogues where cysteine is replaced by aspartic acid or serine, suggesting that C104 is involved in activation and C122 in catalysis.
Knight P, Musoke A J, Gachanja J N, Nene V, Katzer F, Boulter N, Hall R, Brown C G D, Williamson S, Kirvar E, Bell-Sakyi L, Hussain K (1996)

Conservation of neutralizing determinants between the sporozoite surface antigens of Theileria annulata and Theileria parva

Experimental Parasitology 82 (3), 229-241

Abstract

The sporozoite surface antigens SPAG-1 of Theileria annulata and p67 of Theileria parva are postulated to contain determinants necessary for host cell invasion and/or recognition and are both being considered as candidates for inclusion in subunit vaccines. Preliminary data suggest that these are related molecules. In this paper we describe the investigation of the relationship between these sporozoite antigens further by analysis of the immunological cross-reactivity using Mabs and sera raised against each antigen. The cross-reactions were examined by carrying out Western blots, IFA tests, and in vitro sporozoite neutralization assays. In addition, sequence comparison data which clearly establish that these surface antigens are encoded by related genes are presented. The regions of SPAG-1 identified as containing cross-reactive epitopes recognized by p67 antiserum correlated to regions of high predicted homology between p67 and SPAG-1, which are located at their respective N- and C-termini. Furthermore, p67 and SPAG-1 were found to contain cross-reactive determinants responsible for neutralization of sporozoite infectivity in vitro, and at least some of these were located in the C-termini of both molecules. The relevance of these findings to the-possible roles for these molecules in host cell invasion is discussed. (C) 1996 Academic Press, Inc.
Mercer D K, Iqbal M, Miller P G G, McCarthy A J (1996)

Screening actinomycetes for extracellular peroxidase activity

Applied and Environmental Microbiology 62 (6), 2186-2190

Abstract

A diverse collection of actinomycete strains were screened for production of extracellular peroxidase activity by adapting a chemiluminescence analysis system developed for horseradish peroxidase-based enzyme-linked immunosorbent assay. Extracellular peroxidase activity was found to be common but quantitatively variable, and this rapid and sensitive screening system permitted identification of a small group of high-producing strains, A range of spectrophotometric assays were compared for the measurement of peroxidase activity in concentrated culture supernatants of two selected thermophilic streptomycetes, Of these, the peroxide-dependent oxidation of 2,4-dichlorophenol was identified as the most robust and reproducible assay for quantitative studies.

Abstract

Ligation of T-cell receptor (TCR) causes mature T cells to proliferate or, on re-exposure to antigen, can cause them to die by activation-induced cell death (AICD). In proliferative responses, costimulatory and adhesive interactions are required and activation of protein kinase C (PKC) has been shown to be essential. Whether or not interactions involving costimulatory signals and PKC have a role in facilitating AICD remains unclear. Here we have examined the role of CD28/B7 and leucocyte function associated antigen-1 (LFA-1)/intracellular adhesion molecule (ICAM) mediated interactions in AICD triggered by staphylococcal enterotoxin B (SEE) in murine lymph node T cells. We show that, after a primary proliferative response to SEE, LFA-1/ICAM-2 adhesive interactions can play a part in AICD following SEE rechallenge, while B7 and ICAM-1 mediated interactions are not essential for this process. In addition, using a highly selective PKC inhibitor, Ro31.8425, we show that PKC activation is essential for the regulation of AICD by SEE rechallenge.
Bell-Sakyi L, Koney E B M, Dogbey O, Sumption K J (1996)

Heartwater in Ghana: Implications for control of ticks

Tropical Animal Health and Production 28 (2), S59-S64

Abstract

Heartwater, an often fatal rickettsial disease of domestic ruminants transmitted by Amblyomma variegatum ticks, ranks with the A. variegatum-associated skin disease dermatophilosis as a major constraint to the upgrading of livestock productivity in Ghana. An epidemiological survey, using new diagnostic tests, is being carried out to determine the incidence and distribution of hear water and other tick-borne diseases in Ghanaian cattle, sheep and goats. Preliminary results from a longitudinal survey being carried out at sites in the Greater Accra Region indicating that although the vector ticks and the disease agent are widespread outside urban areas, not all animals are being exposed to heartwater during the first few months of life when an inverse age related resistance allows development of immunity without clinical disease. Thus a susceptible sub-population, at risk from heartwater, can exist even in areas of high tick challenge. The significance of these results for present and future tick and disease control strategies is discussed.

Abstract

We have developed an in vitro system in which Staphylococcal enterotoxin B (SEB) activated murine lymph node T cells undergo apoptosis following a rechallenge with SEB. Approximately 50% of the cell are induced to die following SEB rechallenge and this apoptosis is sensitive to the PKC inhibitor Ro3 1.8425 and cyclosporin A. We have also found that cells, previously activated with SEB, can be induced to undergo apoptosis with an anti-a4 mAb (9C10) in the absence of any hrther exposure to antigen. Apoptosis induced in these cells by anti-a4 mAb is inhibited by cyclosporin A and Ro3 1.8425, in a comparable way to restimulation with SEB. We suggest that VLA-4 acitvation may be an important costimulatory factor in the induction of apoptosis in activated mature T cells. This pathway may represent one of the mechanisms whereby certain integrin-cell/ECM interactions can regulate apoptosis in activated mature T cells.

Abstract

The bacteriophage T7 RNA polymerase gene was integrated into the fowlpox virus genome under the control of the vaccinia virus early/late promoter, P-7.5. The recombinant fowlpox virus, fpEFLT7pol, stably T7 RNA polymerase in avian and mammalian cells, allowing transient expression of transfected genes under the control of the T7 promoter. The recombinant fowlpox virus expressing T7 RNA polymerase offers an alternative to the widely used vaccinia virus vTF7-3, or the recently developed modified vaccinia virus Ankara (MVA) T7 RNA polymerase recombinant, a highly attenuated strain with restricted host-range. Recombinant fowlpox viruses have the advantage that as no infectious virus are produced from mammalian cells they do not have to be used under stringent microbiological safety conditions.

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