Amphotericin B as a mycolic acid specific targeting agent in tuberculosis

Abstract

The serious threat of tuberculosis, especially XDR-TB, is a reality in Southern Africa particularly in individuals with HIV/AIDS. Therefore the importance of development of new or improved anti-TB treatment must now be emphasized more than ever. In this study, a model was created to target isoniazid (toxophore) specifically to a cholesterol rich environment where mycobacteria reside in macrophages, by making use of a sterol binding drug, Amphotericin B (haptophore). Isoniazid was covalently linked to Amphotericin B via a Schiff base to a linker molecule, terephthalaldehyde. Although this molecule showed a loss of biological activity, a discovery was made by serendipity that could have great impact in understanding how Mycobacterium tuberculosis enters and survives in the host macrophage. During the testing of the compound, it was discovered that Amphotericin B bound to mycolic acids at least as well as it binds to cholesterol, its natural ligand. This could provide proof of the structural similarity between mycolic acids and cholesterol but many more controls need to be investigated. As cholesterol was previously shown in literature to be critical for entry and survival of Mycobacterium tuberculosis in macrophages, the indication of a structural mimicry between the cell wall mycolic acids and cholesterol and the attraction of these two chemical entities to one another seems to be highly relevant. This characteristic can now be further explored to improve the understanding of the process of entry and survival of Mycobacterium tuberculosis in the macrophage host. Copyright 2006, University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria. Please cite as follows: Benadie, Y 2006, Amphotericin B as a mycolic acid specific targeting agent in tuberculosis, MSc dissertation, University of Pretoria, Pretoria, viewed yymmdd < http://upetd.up.ac.za/thesis/available/etd-04212008-151642 / >