Trypanosomosis is a parasitic disease in man, domestic and wild animals and is of major
economic importance in many parts of the world, particularly in Sub-Saharan Africa.
Trypanosoma congolense, T vivax and T brucei brucei are the major pathogenic
trypanosomes infecting cattle in sub-Saharan Africa. The parasite itself is not directly
responsible for the disease, but rather causes illness through the release of pathogenic factors.
One of the major pathogenic factors released by trypanosomes is proteinases.
Trypanotolerant cattle produce antibodies against a trypanosomal proteinase, congopain, that
inhibit congopain activity. Congopain thus has vaccine potential. This study describes the
mapping of immunogenic epitopes of congopain to identify peptide regions of the protein that
induce enzyme inhibitory antibodies for inclusion in a trypanosome vaccine. This vaccine
approach targets the disease, rather than the parasite by focusing on a pathogenic factor. These
peptides also have potential for use in diagnostic assays. Peptides from the catalytic domain of
a trypanosomal cysteine proteinase, congopain, were selected using an epitope prediction
program. Peptides selected were from the two forms of congopain called CP1 and CP2.
Antibodies against peptide-carrier conjugates were produced in chickens. The antibodies
recognised native congopain, recombinant CP2 and the recombinant catalytic domain (C2).
This suggests that the peptides selected have promise for use in vaccines.
The peptides were also used to determine whether they are natural immunogenic epitopes of
CP2 and thus have potential for use in diagnostic assays. Antibodies in the sera from T.
congolense infected cattle recognised all the peptides in an ELISA. Antibodies in the sera
from C2-immunised, non-infected cattle recognised most of the peptides in an ELISA. In
order to distinguish between T. congolense and T vivax infection, two different peptides from
the C-terminal extensions of CP2 and vivapain were used in ELISA tests with sera from
infected cattle. Although anti-peptide antibodies produced against the two C-terminal
extension peptides were specific for their respective peptides, thereby indicating the
discriminatory power of the peptides selected, there was cross-reactivity by the sera from T.
congolense and T. vivax infected cattle. Optimal antibody binding peptide sequences of these
two peptides need to be identified by testing modified sequences of these two peptides to improve the sensitivity of this assay.
In addition to attempting to define the epitopes of congopain, preliminary studies to increase
the immunogenicity of congopain were also undertaken. Alpha 2-macroglobulin is a natural
host inhibitor of proteinases. Inhibition occurs by entrapment of an active proteinase within
the alpha 2-macroglobulin cage. In addition, it has been demonstrated that antigen complexed
with alpha 2-macroglobulin becomes more immunogenic, resulting in enhanced antigenic
presentation of an entrapped antigen. This study reports the interaction between congopain and
alpha 2-macroglobulin. The preliminary results of this study showing congopain-alpha 2-macroglobulin
interaction could be used to explore the possibility of increasing the
immunogenicity of congopain and congopain epitopes by complexing these to alpha 2-macroglobulin.
Congopain epitopes complexed with alpha 2-macroglobulin could be used to
form a peptide-based vaccine. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2003.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ukzn/oai:http://researchspace.ukzn.ac.za:10413/10108 |
| Date | 28 November 2013 |
| Creators | Mkhize, Pamela Phumelele. |
| Contributors | Coetzer, Theresa Helen Taillefer. |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
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