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Mawela, KG (PhD)

Kedibone Gloria Mawela was born in Ga-Seabe, Mpumalanga, in 1976 and grew up in Alexandra Township, Johannesburg. She received her primary and part of her high school education in Alexandra and matriculated in Giyani, Limpopo Province, in 1994. She graduated from Rhodes University with a BSc in 1999.

She obtained a BScHons in Chemistry from the Medical University of Southern Africa (Medunsa) in 2004 and anMSc in Phytomedicine from the University of Pretoria in 2008. During her MSc studies, she was also placed on the DST-NRF Internship Programme and was based at CSIR Biosciences for the year 2006/2007. Having completed her studies, she joined the CSIR team to pursue her PhD studies.

In her thesis, Evaluation of RANTES analogue expression in Nicotiana benthamiana and Lycopersicon esculentum and their topical microbicidal activity, the promovenda used plants to evaluate expression of the two RANTES (regulated upon activation, normal T cell expressed and secreted) analogues (5P12 and 6P4), which were developed at the University of Geneva. The analogues had higher anti-HIV potency and a strong potential for use as microbicides. Hence they were previously expressed in various biological systems and via chemical synthesis.

Her objective was to prove that they can also be expressed in plants. For her cloning and protein expression strategies, she designed primers to amplify the RANTES analogues with an inclusion of nine nucleotide sequence encoding methionine, valine and serine at the N-terminal ends. The PCR amplicons of the RANTES analogues were then cloned into the pTRA and MagnICON vectors so as to deliver the RANTES genes in plants for transient expression via agrobacterium-mediated transfection.

Unfortunately, the transiently expressed proteins were inactive when biological activity was conducted. This was as a result of the presence of the three added amino acids. On the other hand, the low yields also complicated the study, hence she designed new primers such that the three amino acids were removed and perhaps the yields might also improve. In this way, she fused the RANTES genes to an E. coli heat labile enterotoxin B subunit (LT-B) that cleaves in vivo. Ultimately, the newly designed primers ensured that the transiently expressed protein began with glutamine instead of methionine and better yields were obtained. Transient expression was initially done in Nicotiana benthamiana. As a result of aggregation of the chemokines that drastically affected the yields, the candidate considered a second host with low pH medium that is preferred by chemokines to circumvent aggregation. Lycopersicon esculentum was selected for transient expression due to its citric and malic acid contents. Eventually, she showed that both N. benthamiana and L. esculentum provided a proof of concept that RANTES analogues may be expressed in plants.

Thesis title:

Evaluation of RANTES analogue expression in Nicotiana benthamiana and Lycopersicon esculentum and their topical microbicidal activity.

Supervisor: Prof JN Eloff
External Co-supervisor: Dr E Chakauya (CSIR)
External Co-supervisor: Dr RK Chikwamba (CSIR)
External examiner: Prof O Hartley (University of Geneve, Switzerland)
External examiner: Dr AT Maredza (University of the Witwatersrand)
External examiner: Dr KE Palmer (University of Louisville, USA)
External examiner: Dr O Ruzvidzo (North-West University)