Characterisation and kinetics of aptamer binding to HIV-1 subtype C gp120

Date
2011-03-29
Authors
Millroy, Laura
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Abstract
Aptamers are artificial nucleic acid ligands that can be engineered to bind to with high specificity to a macromolecule. Their binding specificity and small size allow for a range of therapeutic applications. One avenue of research is to develop aptamers with specific and strong affinity to the HIV-1 envelope glycoprotein gp120. Aptamers could act as novel HIV- 1 entry inhibitor drugs or as targeted drug delivery systems to HIV-1 infected cells. Prior to any downstream applications, novel gp120 aptamers need to be biophysically characterised with regards to their target binding characteristics. Eight aptamers (B11, B19, B84, B65, B5, P10, P2 and T58) that have been previously isolated against gp120 and effectively block HIV-1 entry into target cells were used in this study. Secondary structures of selected antigp120 aptamers were computationally determined and analysed. Between one and five structures were predicted for each aptamer. The relative stability of the aptamers was analysed and B11 was shown to have the most stable structure. Using surface plasmon resonance technology aptamer binding was tested and binding kinetics was determined. Five aptamers (B11, B19, B84, B65 and B5) raised against gp120 derived from a subtype B isolate called HIV-1BA-L were tested for binding to monomeric HIV-1DU151 gp120. Kinetic analysis of B11, B65 and B84 followed. The remaining three aptamers (P10, P2 and T58) were raised against whole HIV-1CAP45 pseudovirus and were tested for binding on monomeric HIV-1CAP45 gp120. All three were used for binding kinetic assessment on monomeric HIV-1CAP45 gp120. The dissociation constants were found to be similar to that of previously characterised antigp120 aptamers within the nanomolar range of 16.9 nM to 221 nM. Using the dissociation constant and predicted structure, P2 and B84 were identified as having the greatest potential for further characterisation.
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