Faculty of Natural and Agricultural Sciences
School of Biological Sciences
Department of Biochemistry
Selected Highlights from Research Findings
Since the Department of Biochemistry became involved in 1994 in the study of the wax coat that surrounds the mycobacterial pathogen that causes tuberculosis, a wonder world of structure and mechanism unfolded that has now become one of the frontiers of science in the understanding of how tuberculosis comes about and how it can be managed. The wax coat of mycobacteria consists of a collection of mycolic acids that are unique in structure and characteristic for every species of Mycobacterium that exists.
Until as late as 2000, scientists did not believe that antibodies to free mycolic acids even existed in human TB patients, nor that free mycolic acids played any significant role in establishing the disease, other than providing the pathogen with a wax coat of protection against the chemical warfare of the body's immune system. Prof Jan Verschoor and his group established an international consortium of experts that have reported discoveries proving that mycolic acids induce antibodies in patients that are not deterred by co-infection with HIV, thereby providing a strong surrogate marker of active TB for diagnosing the disease in HIV burdened communities. Convert macrophages into foam cells, a characteristic phenomenon found in lung lesions of TB patients manipulate host immunity in a way that could be exploited to cure experimental asthma in mice. It was found that mycolic acids convert macrophages into foam cells, a characteristic phenomenon found in lung lesions of TB patients to manipulate host immunity. In the laboratory, this was exploited to cure experimental asthma in mice. Structure-function studies are now undertaken on mycolic acids. The year 2007 heralded the publication of the first ever stereo-controlled chemical synthesis of a biologically active mycolic acid, an outcome of research collaboration with University of Bangor, UK, where one of our PhD students participated in the break-through. All the main subclasses of mycolic acids can now be chemically synthetised, as well as any structural variant to determine structure-function relationships. A UP MSc student is currently modelling the structures of the mycolic acids by molecular dynamics in Bangor. Prof Baird, who leads the group in Bangor, has been appointed as extraordinary professor to UP. A recent PhD graduate from his group is now a post-doctoral fellow in Pretoria. The collaboration is financially supported by the Royal Society and NRF. Prof Verschoor is currently on sabbatical in Bangor as a visiting professor, through a Commonwealth Fellowship supported by the British Council.
Contact person: Prof JA Verschoor.
Ticks place a tremendous economical strain on agriculture, more so in deprived developing countries in which alternative control measures are not established and freely available. To date, the Boophilus, Rhipicephalus, Hyalomma and Amblyomma species have been identified as the economically most significant species that need to be controlled. Boophilus microplus, in which increasing acaracide resistance occurs and its recent introduction into West Africa is of growing concern. To date, only a single recombinant vaccine based on the gut glycoprotein Bm86 of B. microplus has been extensively validated and is commercially available (Willadsen, Australia). Validation of Bm86 homologues from other Boophilus and Rhipcephalus species are currently actively pursued and could result in a vaccine specific for vaccinating against Boophilus. Although this recombinant vaccine effectively decreases the weight and offspring of Boophilus ticks, co-treatment with acaracides are still required. During the past few years, numerous vaccine candidates have been identified but their validation remains elusive. The most extensively studied candidate is subolesin (4D8) identified from the Lyme disease-transmitting tick, Ixodes scapularis (de la Fuente, USA). It has been shown to very significantly impede digestion and reproduction of some 10 ixodid tick species belonging to 6 genera. Our group has identified three proteins interacting with subolesin. The use of anti-hemostatics as vaccines has also been investigated using boophilin G2 (a thrombin inhibitor) and the B. microplus homologue of ixolaris (a factorX inhibitor). Quantitative real-time PCR of these two candidates revealed that both transcripts are expressed throughout the B. microplus lifecyle in most tick tissues, but most abundantly in gut. Although in vivo gene silencing of these two candidates did not reveal a significant phenotype, gut abnormalities were detected in some ticks from the boophilin-silenced group. Transcriptional responses were identified between boophilin and ixolaris, which did not occur towards salp14 (another fX-inhibitor). The observations that boophilin is both an exposed- and concealed antigen in combination with the observed phenotype in gut tissue, attest to vaccination trials. The possibility of a continuous host immune system boosting effect as well as a more severe effect on gut tissue (tick digestion) when used in combination with Bm86 is envisaged. Future studies on the physiological roles and transcriptional responses of boophilin and ixolaris is in progress. The need for more vaccine candidates are actively explored in our laboratory by global reverse genetic approaches such as RNA-interference libraries and DNA microarrays.
Contact person: Dr C Maritz-Olivier.
Ticks place a tremendous economical strain on agriculture, more so in deprived developing countries in which alternative control measures are not established and freely available. To date, the Boophilus, Rhipicephalus, Hyalomma and Amblyomma species have been identified as the economically most significant species that need to be controlled. Boophilus microplus, in which increasing acaracide resistance occurs and its recent introduction into West Africa is of growing concern. To date, only a single recombinant vaccine based on the gut glycoprotein Bm86 of B. microplus has been extensively validated and is commercially available (Willadsen, Australia). Validation of Bm86 homologues from other Boophilus and Rhipcephalus species are currently actively pursued and could result in a vaccine specific for vaccinating against Boophilus. Although this recombinant vaccine effectively decreases the weight and offspring of Boophilus ticks, co-treatment with acaracides are still required. During the past few years, numerous vaccine candidates have been identified but their validation remains elusive. The most extensively studied candidate is subolesin (4D8) identified from the Lyme disease-transmitting tick, Ixodes scapularis (de la Fuente, USA). It has been shown to very significantly impede digestion and reproduction of some 10 ixodid tick species belonging to 6 genera. Our group has identified three proteins interacting with subolesin. The use of anti-hemostatics as vaccines has also been investigated using boophilin G2 (a thrombin inhibitor) and the B. microplus homologue of ixolaris (a factorX inhibitor). Quantitative real-time PCR of these two candidates revealed that both transcripts are expressed throughout the B. microplus lifecyle in most tick tissues, but most abundantly in gut. Although in vivo gene silencing of these two candidates did not reveal a significant phenotype, gut abnormalities were detected in some ticks from the boophilin-silenced group. Transcriptional responses were identified between boophilin and ixolaris, which did not occur towards salp14 (another fX-inhibitor). The observations that boophilin is both an exposed- and concealed antigen in combination with the observed phenotype in gut tissue, attest to vaccination trials. The possibility of a continuous host immune system boosting effect as well as a more severe effect on gut tissue (tick digestion) when used in combination with Bm86 is envisaged. Future studies on the physiological roles and transcriptional responses of boophilin and ixolaris is in progress. The need for more vaccine candidates are actively explored in our laboratory by global reverse genetic approaches such as RNA-interference libraries and DNA microarrays.
Contact person: Dr ARM Gaspar.
Ticks place a tremendous economical strain on agriculture, more so in deprived developing countries in which alternative control measures are not established and freely available. To date, the Boophilus, Rhipicephalus, Hyalomma and Amblyomma species have been identified as the economically most significant species that need to be controlled. Boophilus microplus, in which increasing acaracide resistance occurs and its recent introduction into West Africa is of growing concern. To date, only a single recombinant vaccine based on the gut glycoprotein Bm86 of B. microplus has been extensively validated and is commercially available (Willadsen, Australia). Validation of Bm86 homologues from other Boophilus and Rhipcephalus species are currently actively pursued and could result in a vaccine specific for vaccinating against Boophilus. Although this recombinant vaccine effectively decreases the weight and offspring of Boophilus ticks, co-treatment with acaracides are still required. During the past few years, numerous vaccine candidates have been identified but their validation remains elusive. The most extensively studied candidate is subolesin (4D8) identified from the Lyme disease-transmitting tick, Ixodes scapularis (de la Fuente, USA). It has been shown to very significantly impede digestion and reproduction of some 10 ixodid tick species belonging to 6 genera. Our group has identified three proteins interacting with subolesin. The use of anti-hemostatics as vaccines has also been investigated using boophilin G2 (a thrombin inhibitor) and the B. microplus homologue of ixolaris (a factorX inhibitor). Quantitative real-time PCR of these two candidates revealed that both transcripts are expressed throughout the B. microplus lifecyle in most tick tissues, but most abundantly in gut. Although in vivo gene silencing of these two candidates did not reveal a significant phenotype, gut abnormalities were detected in some ticks from the boophilin-silenced group. Transcriptional responses were identified between boophilin and ixolaris, which did not occur towards salp14 (another fX-inhibitor). The observations that boophilin is both an exposed- and concealed antigen in combination with the observed phenotype in gut tissue, attest to vaccination trials. The possibility of a continuous host immune system boosting effect as well as a more severe effect on gut tissue (tick digestion) when used in combination with Bm86 is envisaged. Future studies on the physiological roles and transcriptional responses of boophilin and ixolaris is in progress. The need for more vaccine candidates are actively explored in our laboratory by global reverse genetic approaches such as RNA-interference libraries and DNA microarrays.
Contact person: Prof AWH Neitz.
The fight against malaria has now been stepped up through the application of cutting-edge technologies. The Malaria Research Programme under Prof AI Louw and Dr L Birkholtz is applying DNA microarray and proteomic technologies to identify and validate drug targets in the human malaria parasite, Plasmodium falciparum. These parasites have an absolute requirement for highly charged polyamines. By depleting the parasites of their endogenous polyamines, an indication can be obtained of the functions of the polyamines as well as validation of this pathway as an antimalarial target. The use of functional genomics in antimalarial drug discovery was reviewed extensively by us (L Birkholtz et al, 2006; L Birkholtz et al, Acta Tropica, 2007). Polyamine-dependent transcripts indicative of cell cycle arrest were identified as well as a resultant hypermethylated state in the parasite due to increased S-adenosylmentionine levels. Moreover, a feedback response of the parasite transcriptome was observed after the perturbation thereby providing evidence for gene regulation at the transcriptional level in Plasmodia. Furthermore, the work provided the first indication of remarkable, alternative compensatory responses induced in the parasite to overcome the lack of intracellular polyamines. In addition, the cytostatic effect of these inhibitors was shown to result in a unique profile discernable from usual cytostatic responses (Clark et al, Biol Chem, 2007; van Brummelen et al, 2007 submitted). This work will have a significant impact on the further development of polyamines and their derivatives as antimalarial drug targets. The expertise of this group is now used to establish the Functional Genomics Core Expertise Group of the newly established South African Malaria Initiative (SAMI). Collaborators include Prof M Llinas (Princeton University, USA) and Dr E Marechal (CNRS, France) and involve three PhD students. The work is funded in part by the Department of Science and Technology through SAMI and microarray experiments were performed with the help of the African Centre for Gene Technologies microarray facility.
Contact person: Prof AI Louw.
The fight against malaria has now been stepped up through the application of cutting-edge technologies. The Malaria Research Programme under Prof AI Louw and Dr L Birkholtz is applying DNA microarray and proteomic technologies to identify and validate drug targets in the human malaria parasite, Plasmodium falciparum. These parasites have an absolute requirement for highly charged polyamines. By depleting the parasites of their endogenous polyamines, an indication can be obtained of the functions of the polyamines as well as validation of this pathway as an antimalarial target. The use of functional genomics in antimalarial drug discovery was reviewed extensively by us (L Birkholtz et al, 2006; L Birkholtz et al, Acta Tropica, 2007). Polyamine-dependent transcripts indicative of cell cycle arrest were identified as well as a resultant hypermethylated state in the parasite due to increased S-adenosylmentionine levels. Moreover, a feedback response of the parasite transcriptome was observed after the perturbation thereby providing evidence for gene regulation at the transcriptional level in Plasmodia. Furthermore, the work provided the first indication of remarkable, alternative compensatory responses induced in the parasite to overcome the lack of intracellular polyamines. In addition, the cytostatic effect of these inhibitors was shown to result in a unique profile discernable from usual cytostatic responses (Clark et al, Biol Chem, 2007; van Brummelen et al, 2007 submitted). This work will have a significant impact on the further development of polyamines and their derivatives as antimalarial drug targets. The expertise of this group is now used to establish the Functional Genomics Core Expertise Group of the newly established South African Malaria Initiative (SAMI). Collaborators include Prof M Llinas (Princeton University, USA) and Dr E Marechal (CNRS, France) and involve three PhD students. The work is funded in part by the Department of Science and Technology through SAMI and microarray experiments were performed with the help of the African Centre for Gene Technologies microarray facility.
Contact person: Dr L Birkholtz.
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