The objective of the present study was to examine the ways that the T. evansi components
interact with the host by investigating the components of tire parasite which acted as antigens during
infection and to study the dynamics of some of these antigens during infection. Results from this study
could help in identifying new diagnostic reagents, a better understanding of existing diagnostic
methods and target antigen for production of vaccines.
The antigenic components of intact and trypsin-treated T. evansi were identified. Thirty nine
protein bands were detected in the trypanosomal preparations using sodium dodecyl sulphate
polyacrylamide gel electrophoresis (SDS-PAGE). Twenty seven of these components were identified as
antigens using immunoblotting against sera from infected rabbits and rabbits immunised with a range
of soluble parasite materials. The solubilisation procedure and immunisation method affected the
number of antigens recognised by these sera. The trypsin-treated parasites failed to produce any
antibody response as measured by immunoblotting and ELISA
y response as measured by immunoblotting and ELISA.
Two soluble antigens identified by immunoblotting were selected for further study, a trypsin
sensitive component of ~ 52 k.Da which was cleaved from the parasite by the process of trypsinisation
and a non-surface component of ~ 42 k.Da which was recognised strongly by sera from infected rabbits
and rabbits immunised with the parasite soluble materials. Both antigens were also immunogens as
soluble extract. A third antigen of molecular weight of ~72 k.Da recognised by monoclonal antibodies
raised to the intact living trypanosomes was also included in the study
Polyclonal monospecific antibodies were produced to both the 52 k.Da and 42 k.Da antigens.
The 72 k.Da monoclonal antibody and both polyclonal antibodies were labelled separately with biotin
and horseradish peroxidase. These labelled antibodies were used to develop an enzyme-linked
immunosorbent assay (antigon ELISA) to dctoct their corresponding antigens in the blood and tissue
extracts of infected animals, and in immunohistochemical tests on cryostat sections to localise the
antigens in the tissues.
The three antigens were detected in the blood of infected animals at different times. The 52
k.Da antigen was first detected in the blood 6 days after infection, followed by the 42 k.Da antigen 7
days post-infection and the 72 k.Da antigen 8 days after infection. Following the administration of
Berenil, the 72 k.Da was cleared from the circulation the following day. The two other antigens were
cleared from the circulation 2 days after treatment. In the tissue extracts, the 42 k.Da antigen was
detected extravascularly from the spleen, brain and kidneys. In case of the 52 k.Da, it was also detected
from the heart and lungs in addition to the above organs. The 72 k.Da antigen was, however, not
detected in any of the tissue extracts. On cryostat sections prepared from the above organs however,
none of the antigens was detectable.
The 52 k.Da antigen identified as an invariant antigen is a possible candidate for the
diagnosis of infection but only in areas where T. evansi is the only trypanosome species present due to
The difference in the dynamics and localisation of the trypanosomes antigens warrants further
investigation and provides a better understanding of the host-parasite interaction.