Browsing by Author "Chikwamba, Rachel"

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    Open Access
    Riding the tide of biopharming in Africa: Considerations for risk assessment
    (2006) Chakauya, Ereck; Chikwamba, Rachel; Rybicki, Edward P
    In the past few years, plant biotechnology has gone beyond traditional agricultural production of food, feed and fibre, and moved to address more complex contemporary health, social and industrial challenges. The newera involves production of novel pharmaceutical products, speciality and fine chemicals, phytoremediation and production of renewable energy resources to replace nonrenewable fossil fuels. Plants have been shown to provide a genuine and low-cost alternative production system for high-value products. Currently, the principal plant-made products include antibodies, feed additives, vaccine antigens and hormones for human and animal health, and industrial proteins. Despite the unique advantages of scalability, cost and product safety, issues of politics, environmental impact, regulation and socioeconomics still limit the adoption of biopharmaceuticals, especially in the developing world. Plant-based production systems have further complicated biosafety, gene flow and environmental impact assessments with generally genetically modified plants, topics that are already partially understood. This article provides a background to biopharming, highlighting basic considerations for risk assessment and regulation in developing countries, with an emphasis on plant-based vaccine production in South Africa.
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    Open Access
    Targeted expression of the anti-HIV microbicide lectin griffithsin in maize and tobacco
    (2013) Stark, Hester Catharina (Therese); Rybicki, Ed; Chikwamba, Rachel
    Plants are emerging as cost friendly alternative production systems for a variety of pharmaceuticals. Numerous therapeutic proteins have been produced in plant systems (Giddings et al., 2000; Ma et al., 2003). Protein based microbicides,-namely, neutralising antibodies and peptide lectins- lend themselves to production in plants (De Muynck et al., 2010; Matoba et al., 2010; Sexton et al. 2006; O’Keefe et al., 2009). One of these lectins, namely Griffithsin (GRFT) was isolated from the blue green algae Griffithsia and is being developed as a leading anti-HIV microbicide peptide (Mori et al., 2005). As literature indicates, the optimal production of any protein is an empirical experimentation with different host systems, vector systems, codon optimisations and subcellular targeting. (Maclean et al., 2007; Yang et al., 2005). The latter sometimes results in unexpected locations which might reflect on an inherent property of the protein itself or specifically be associated with the plant organ involved (Chikwamba et al., 2003). This again can influence protein yield- and activity, and impact downstream purification. In this study we aimed to compare expression levels using both Zea mays (maize) and Nicotiana benthamiana (tobacco) with relevant vector technologies. We expressed GRFT in maize using an endosperm specific maize expression vector with and without a signal peptide. In tobacco we utilised both the pTRA binary vector and magnICON deconstructed viral vector system to express GRFT with different subcellular targeting signals.