Studies on Altered Gene Expression in Theileria annulata Infected Cells and in Uninfected Cells of a Related Lineage

Dando, Caroline (1997) Studies on Altered Gene Expression in Theileria annulata Infected Cells and in Uninfected Cells of a Related Lineage. PhD thesis, University of Glasgow.

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Abstract

The macroschizont stage of the protozoan parasite Theileria annulata has the unique ability to immortalise the bovine leukocyte in which it resides. Little is known of the mechanisms by which the parasite is able to induce immortalisation, but a number of associated changes to host cell gene expression have been documented. One such modification is an alteration in the profile of surface polypeptides expressed by the infected cell. One of these infection associated surface antigens is recognised by monoclonal antibody 4115. In T. annulata infected cells this molecule was shown to have a variable molecular mass of between 90 and 125 kDa when different cell lines were analysed. Immune bovine sera failed to recognise this antigen and it is likely that it is encoded by a bovine gene, the expression of which is up-regulated by the presence of the parasite. Characterisation of this antigen and investigation of how its production is elevated upon infection would provide insights into its possible function, and allow a clearer understanding of how the parasite modulates host cell gene expression. To initiate these studies immunoaffinity chromatography was used to purify the antigen (TaHBL20/125) from T. annulata (Hissar) infected cells, and the N terminus of the polypeptide was sequenced. Homology was found between this peptide sequence and the human intracellular adhesion molecule, ICAM-1. Information from the amino acid sequence data was then used to design degenerate oligonucleotide pools and an infected cell cDNA library was screened with these probes. Considerable problems were encountered in the design of the oligonucleotides and the gene of interest was not isolated. However, establishment of antigen purification protocols provide the basis for further study. T. annulata is known to infect cells of the monocyte/macrophage and B cell lineages. TaHBL20/125 could therefore represent an up-regulated host molecule associated with cells of a related lineage. Monoclonal antibody 4115 was found to recognise an antigen of 160 kDa in the human leukemic cell line HL-60. Furthermore, differentiation of HL-60 towards granulocytes resulted in a significant increase in the expression of the g160 kDa antigen. Previous studies on differentiation in T. annulata have drawn general parallels between the processes of differentiation in the parasite and higher eukaryotic cells. The reactivity shown by monoclonal antibody 4H5 against HL-60 during differentiation to granulocytes was used as a sensitive marker to extend these parallel studies. The results indicated that during differentiation of HL-60 there is a reversible phase with respect to the 4H5 epitope and that the ability to differentiate is modulated by conditions which alter the growth rate relative to division. As similar findings have been found in T. annulata it is proposed that the basic mechanisms controlling differentiation in higher eukaryotes and protozoan cells may be related, reflecting the operation of a primitive mechanism which has been retained by lower and higher eukaryotes.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Additional Information: Adviser: Brian Shiels
Keywords: Animal diseases, Parasitology
Date of Award: 1997
Depositing User: Enlighten Team
Unique ID: glathesis:1997-75847
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 19 Nov 2019 17:44
Last Modified: 19 Nov 2019 17:44
URI: http://theses.gla.ac.uk/id/eprint/75847

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