​Tick vector biology

Project Manager: Dr Ben Mans

Discovery of arthropod proteins involved in a blood-feeding lifestyle (in collaboration with OVR-New Generation Vaccines Programme): Specific objectives for the immediate future

a) Discovery of tick vaccine candidates
b) Tick genomics and transcriptomics
c) Expand our knowledge base for tick vector biology & systematics
d) Systematics, life cycle & host relationships of Nuttalliellia (missing link/live fossil).

Discovery of the proteins involved in a blood-feeding lifestyle encompass two basic approaches: Identification of proteins and their characterization & Identification of proteins involved in a blood-feeding lifestyle.

Identification of proteins involved in blood-feeding behavior, consists of the description of the proteomes of various organs from blood-feeding organisms. Proteomes are described primarily on nucleic acid level by the construction of organ-specific cDNA libraries or via genome analysis. This gives a transcriptomic view of potential proteins expressed in the specific organ in question. Such transcriptomes needs to be verified on protein level to determine levels of expression and or potential modifications to proteins. This is done primarily, via proteomic methodology that fractionates crude organ extracts selectively by exploiting protein specific properties such as molecular mass, iso-electric point and hydrophobicity. Basic techniques include one and two-dimensional electrophoresis, liquid chromatography, followed by Edman sequencing and peptide mass fingerprinting. This allows for the establishment of proteomic fingerprints of organs that can investigated for dynamic change induced by the environment or the developmental stage of the organism.

Characterization of proteins involved in a blood-feeding lifestyle: Proteins identified using transcriptome and protein methodologies are analyzed for bioinformatical content that allows their assignment to specific protein-families and primitive annotation of function. This information once curated remains a basic resource for future research that can be stored in propriety or public databases. Functional confirmation and elucidation of molecular mechanisms of action are essential steps for in-depth description of identified proteins. This is accomplished by characterization of wild-type proteins purified from their organs of origin and by expression of recombinant proteins in heterologous systems. Localization of proteins to sub-cellular level, identification of antigenic potential and functional modulation by knock-down strategies is important for further validation of function and vaccine potential. Testing of promising proteins in vaccine trials will be the eventual outcome.

Development of an attenuated heartwater vaccine  

Project Leader: Lefoka Molepo

Heartwater, caused by Ehrlichia ruminantium is probably the most economically important livestock disease in South Africa, and it is estimated to cost the country approximately R400 million annually. The live-blood vaccine developed by Onderstepoort half a century ago is still marketed as the only commercially available vaccine, but it does not protect against all field isolates of the heartwater parasite and is cumbersome to users, having to be inoculated intravenously. Innovative research, resulted in the development of an attenuated bacterial vaccine prepared from tissue culture. Tests have shown that: vaccination of cattle, sheep, Boer and Angora goats with culture material by intramuscular route was safe and no treatment of vaccine reactions were required; all animals were protected against a subsequent lethal intravenous needle challenge from homologous and heterologous virulent field isolates; vaccinated sheep infested with infected ticks were fully protected. All results, showing the attenuated culture-derived vaccine as an ideal candidate for commercial development and testing.

>>> Back to Epidemiology, vaccines and diagnostics dev​​elopment​