Growth, Differentiation and the Regulation of Trypanosoma brucei Infections

Aslam, Nasreen (1992) Growth, Differentiation and the Regulation of Trypanosoma brucei Infections. MSc(R) thesis, University of Glasgow.

Abstract

The experiments described in this thesis were conducted to determine how trypanosome growth may regulate the course of an infection. The question of whether cloned stocks of Trypanosoma brucei differ in the courses of infection that they produce in inbred mice was addressed. Accurate parasitaemic profiles were obtained for 6 cloned stocks of trypanosomes and from a comparison of these it was shown that the courses of infection differed between them. Infections with one of the cloned stocks were characterised by the occurence of a high parasitaemia and no remission of infection whilst infections with another were characterised by a low parasitaemia and several cycles of remission and recrudescence. Parasitaemic profiles obtained for the other four cloned stocks were intermediate between these two extremes. Parasitaemic profiles were also compared between three lines of trypanosomes derived from the same cloned stock but differing in the number of rapid syringe-passages undergone through mice. Parasitaemias were shown to increase as a result of rapid syringe-passaging. Rates of trypanosome population growth, replication of slender forms and differentiation from slender to stumpy forms were compared between cloned stocks of trypanosomes known to differ in the courses of infection that they produced in inbred mice. The objective of this study was to determine whether the observed differences in the courses of infection could be explained by differences in these rates. When cloned stocks were compared a positive correlation was observed between the rate of growth, rate of replication and course of infection: high parasitaemias were associated with faster rates of growth and replication. This correlation was not observed however, in the second comparison between the with three trypanosome lines of the same genotype but different passage histories. From these results it would appear that the basis of the variation in the courses of infection differs between trypanosomes in the laboratory and in the field. A relationship was not observed between rates of trypanosome differentiation and courses of infection in either of the two comparisons made. The relationship between variable antigen type (VAT) expression and trypanosome growth rates was reinvestigated. Growth rates in mice were compared between pairs of cloned trypanosome populations each of which homogeneously expressed a different VAT. Two groups of VATs were compared and within each group, the lines expressing different VATs were of the same passage history. In a sensitive assay of relative growth, no significant differences were found in 4 of 6 experiments using the first group of VATs and in 1 of 3 experiments using the second group. In those experiments where a difference was observed the data were analysed further to determine the differences in population doubling times. These differences were less than 10% in all cases. It was concluded that variable antigen expression will exert no effect on rates of trypanosome population growth.

• Item Type: Thesis (MSc(R))
• Qualification Level: Masters
• Additional Information: Adviser: Mike Turner
• Keywords: Parasitology
• Date of Award: 1992
• Depositing User: Enlighten Team
• Unique ID: glathesis:1992-75410
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 19 Nov 2019 20:12
• Last Modified: 19 Nov 2019 20:12
• URI: https://theses.gla.ac.uk/id/eprint/75410