| dc.description.abstract | Three members of the Salivarian trypanosomes, namely, Trypanosoma vivax,
T congolense and T brucei brucei, cause African animal trypanosomosis. In the
. attempt to arrive at an effective vaccine, research has focused on identifying
trypanosome antigens that would elicit imrnunoprotection. Variant surface
glycoproteins, (VSGs), the predominant proteins forming the 12-15 nm thick surface
coat of the parasites, are strong immunogens, but are ineffectual as components of a
vaccine since they are hyper-variable and alter through a process termed antigenic
variation. More attention is consequently being given to antigens that are non-variant
or that have a significantly reduced capacity to vary. Certain domestic and wild
animals such as the African Cape Buffalo (Synercus caffer) display a level of
resistance to the disease (trypanotolerance). Part of the mechanism of
trypanotolerance may be attributed tothe ability of these ungulates to raise antibodies
against vital trypanosome antigens.
In this study, serum from trypanosome-infected Buffalo was used to screen T
congolense cDNA and genomic DNA expression libraries with the aim of identifying
genes encoding non-variant antigens recognised during an infection to determine
whether these constitute vaccine candidate antigens. A variety of techniques were
employed to purify and characterise selected clones of interest. These included:
nucleic acid preparation, PCR amplification, restriction enzyme analysis, agarose gel
electrophoresis, Southern and Northern analyses and sequencing.
A VSG-like gene was identified and cloned for characterisation by
sequencing. Southern analysis showed that this gene occurs as a single copy within
the T congolense IL 3000 and IL 1180 genomes. In addition, through Northern
analysis, it was determined that it is expressed in both the metacyclic and bloodstream
stages of the parasite. It was observed that the putative protein encoded by this gene
is similar to 117, an invariant T brucei flagellar antigen with noted diagnostic potential.
Based on preliminary evidence of its invariance and immunogenicity, the putative
protein may hold potential as a candidate vaccine antigen. Further work should be
done to determine the cellular localisation of the putative protein as well as its
protective potential. | en |
