|dc.description.abstract||Nearly half of all individuals living with HIV worldwide at present are woman and
the best current strategy to prevent sexually transmitted HIV is antiretrovirals (ARVs).
Microbicides are ARV’s which directly target viral entry and avert infection at mucosal
surfaces. However, most promising ARV entry inhibitors are biologicals which are costly
to manufacture and deliver to resource-poor areas. Microbicides formulated as simple
gels, which are currently not commonly used in ARV therapy, show immense potential
for use in prevention and treatment of multidrug-resistant viral infections in developing
Among the most potent HIV entry inhibitory molecules are lectins, which target the
high mannose N-linked glycans which are displayed on the surface of HIV envelope
glycoproteins. Of the microbicides, the red algal protein griffithsin (GRFT) has potent
anti-HIV inhibitory activity and is active by targeting the terminal mannose residues on
high mannose oligosaccharides. It has a total of 6 carbohydrate binding sites per
homodimer, which likely accounts for its unparalleled potency. The antiviral potency of
GRFT, coupled with its lack of cellular toxicity and exceptional environmental stability
make it an ideal active ingredient of a topical HIV microbicide.
Scytovirin (SVN) is an equally potent anti-HIV protein, isolated from aqueous
extracts of the cyanbacterium, Scytonema varium. Low, nanomolar concentrations of
SVN have been reported to inactivate laboratory strains and primary isolates of HIV-
1. The inhibition of HIV by SVN involves interactions between the protein and HIV-1
envelope glycoproteins gp120, gp160 and gp41.
Current recombinant production methods for GRFT and SVN molecules are
unfortunately hampered by inadequate production capacities. This project therefore
aimed to determine if these molecules can be produced in plant cell culture systems.
The transgenic tobacco cell culture system was evaluated to determine if it can be an
alternative, cost effective production system for these molecules.
Results of the study show that the microbicide genes can be cloned into plant
transformation vectors, used to successfully transform SR1 tobacco cell lines and
adequately produce 3.38ng and 10.5ng of GRFT and SVN protein respectively, per
gram of SR1 tobacco callus fresh weight.
The promising results attained in this study form the basis for further work in
optimising plant cell based production systems for producing valuable anti-HIV
microbicides, a possible means to curbing the elevated HIV infection rates worldwide.||en_US