17th International HIV Drug Resistance Workshop 10-14 June 2008, Sitges, Spain

STRUCTURAL EXPLANATIONS TO ALTERED DRUG RESISTANCE PATHWAYS IN HIV-1 NON-CLADE B PROTEASES

Antivir Ther. 2008; 13(Suppl. 3):A42 (abstract no. 37)

RM Bandaranayake¹, C Ng¹, M Kolli¹, M Prabu-Jeyabalan¹, M Nalam¹, J Kakizawa², A Heroux3, NM King¹, W Sugiura² and CA Schiffer^1
1University of Massachusetts Medical School, Massachusetts, USA; ²National Institute of Infectious Diseases, Tokyo, Japan; ³Brookhaven National Laboratory, New York, USA

BACKGROUND: The majority of HIV-1 infections across the world result from non-B clades. CRF01_AE is predominantly seen in Southeast Asia and the protease differs by ~10% when compared with the clade B protease. CRF01_AE polymorphisms are often associated with drug resistance in the clade B protease. CRF01_AE protease has been observed to develop the unique N88S mutation in response to nelfinavir (NFV) therapy, which is not commonly seen in clade B protease. We present here, structural and binding thermodynamic data on CRF01_AE protease in order to explain how sequence polymorphisms within CRF01_AE protease might affect its activity and to explain the altered NFV resistance pathway observed in CRF01_AE.

METHODS: The crystal structure of HIV-1 CRF01_AE N88S protease in complex with darunavir (DRV) was determined to a resolution of 1.76 Å. The structure was compared with the clade B protease–DRV structure to determine effects of sequence polymorphisms on protease structure and substrate binding. Binding constants and thermodynamic parameters for CRF01_AE and clade B protease were determined by isothermal titration calorimetry.

RESULTS: Calorimetric data indicate that wild-type CRF01_AE protease binding is tenfold and twofold weaker to NFV and DRV, respectively. The CRF01_AE structure shows a significant change in the flap hinge region of the protease when compared with the clade B structure. The CRF01_AE flap hinge packs against the core region of the protease via a network of unique hydrogen bonds that are not seen in the clade B structure. The Ser88 side chain in the CRF01_AE structure is involved with a novel network of hydrogen bonds and interacts with the side chain of Asp30. This is likely to disrupt a crucial hydrogen bond required for NFV binding.

CONCLUSIONS: Structural data indicate that sequence polymorphisms in HIV-1 CRF01_AE cause significant structural changes within the protease when compared with clade B protease. Calorimetric data suggest that wild- type CRF01_AE protease might have lower affinity for NFV and DRV. This weakened affinity may permit the alternative pathway for NFV resistance via N88S, which is a mutation outside the active site.

2008-06-10
37

Copyright © 2008 - International Medical Press Ltd.. Reproduction of this abstract (other than one copy for personal reference) must be cleared through the International Medical Press Ltd. 2-4 Idol Lane, London EC3R 5DD UK.