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Toxins 2012, 4(7), 554-567; doi:10.3390/toxins4070554
Article

Humanized-Single Domain Antibodies (VH/VHH) that Bound Specifically to Naja kaouthia Phospholipase A2 and Neutralized the Enzymatic Activity

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Received: 19 June 2012 / Revised: 26 June 2012 / Accepted: 6 July 2012 / Published: 19 July 2012
(This article belongs to the Special Issue Toxin-Antibody Interactions)
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Abstract

Naja kaouthia (monocled cobra) venom contains many isoforms of secreted phospholipase A2 (sPLA2). The PLA2 exerts several pharmacologic and toxic effects in the snake bitten subject, dependent or independent on the enzymatic activity. N. kaouthia venom appeared in two protein profiles, P3 and P5, after fractionating the venom by ion exchange column chromatography. In this study, phage clones displaying humanized-camel single domain antibodies (VH/VHH) that bound specifically to the P3 and P5 were selected from a humanized-camel VH/VHH phage display library. Two phagemid transfected E. coli clones (P3-1 and P3-3) produced humanized-VHH, while another clone (P3-7) produced humanized-VH. At the optimal venom:antibody ratio, the VH/VHH purified from the E. coli homogenates neutralized PLA2 enzyme activity comparable to the horse immune serum against the N. kaouthia holo-venom. Homology modeling and molecular docking revealed that the VH/VHH covered the areas around the PLA2 catalytic groove and inserted their Complementarity Determining Regions (CDRs) into the enzymatic cleft. It is envisaged that the VH/VHH would ameliorate/abrogate the principal toxicity of the venom PLA2 (membrane phospholipid catabolism leading to cellular and subcellular membrane damage which consequently causes hemolysis, hemorrhage, and dermo-/myo-necrosis), if they were used for passive immunotherapy of the cobra bitten victim. The speculation needs further investigations.
Keywords: snake bite; snake venom; phospholipase A2 (PLA2); single domain antibody (SdAb); VH/VHH; homology modeling; molecular docking snake bite; snake venom; phospholipase A2 (PLA2); single domain antibody (SdAb); VH/VHH; homology modeling; molecular docking
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Chavanayarn, C.; Thanongsaksrikul, J.; Thueng-in, K.; Bangphoomi, K.; Sookrung, N.; Chaicumpa, W. Humanized-Single Domain Antibodies (VH/VHH) that Bound Specifically to Naja kaouthia Phospholipase A2 and Neutralized the Enzymatic Activity. Toxins 2012, 4, 554-567.

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