5th International Workshop on HIV Drug Resistance & Treatment Strategies


4-8 June 2001, Scottsdale, Arizona

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[TITLE:] EMERGENCE OF AN UNUSUAL RESISTANCE PROFILE FOR CONOCURVONE, AN EARLY-STAGE INHIBITOR OF HIV-1 REPLICATION

[AUTHOR(S):] M Kearney1,2, L Pallansch1, S Cox3, J Coates3 and RW Buckheit Jr1
1 Southern Research Institute, Frederick, Md., USA; 2 National Cancer Institute, Frederick, Md., USA; and 3 AMRAD Operations Pty, Victoria, Australia
Antivir Ther. 2001;6 Suppl 1:11

A unique inhibitor of HIV-1, conocurvone, was isolated from extracts of the Australian shrub Conospermum incurvum. This compound, a trimeric napthoquinone, is a potent inhibitor of HIV-1-induced cell killing (EC50<20 µM) that is relatively strain specific (HIV-1RF > HIV-1NL4-3 >>> HIV-1IIIB). Recent in vitro mechanism of action studies revealed that conocurvone possesses dual inhibitory activity against both HIV-1 integrase and HIV cell-mediated fusion. To determine whether either of these mechanisms is a biologically relevant viral target for conocurvone, a drug-resistant HIV-1RF virus was generated by passaging under drug selection. This virus, denoted cono-R, was used as a template to identify conocurvone resistance-engendering mutations and to determine the mechanism of action of conocurvone. Genotypic analysis of this cono-R virus revealed four amino acid changes in gp120, four in gp41, and none in integrase, suggesting that conocurvone targets the HIV-1 envelope protein. Additionally, several of the envelope mutations that arose under conocurvone selection have also been identified in CD4-independent viruses. One of the gp41 mutations introduces a premature stop codon at position W766 and, as a result, truncated more than 100 amino acids from the cytoplasmic tail of the HIV envelope protein, similar to some CD4-independent viruses. Interestingly, when an analogous proviral clone (HIV-1pNL4-3 W766*) was constructed, the resultant virus was replication-defective yet able to fully induce syncitia formation in CEM-SS cells. Furthermore, three of the cono-R gp120 mutations, V64A, G145E and N315K, conferred conocurvone-resistance to NL4-3 when introduced into the pNL4-3 provirus. The G145E and N315K mutations are located within the V1/V2 and the V3 loop, respectively. These variable loops have been implicated in determining viral co-receptor usage. These resistance selection data indicate that conocurvone targets gp120 of HIV-1 and inhibits HIV fusion in T cells. This study suggests that HIV-1 may escape the activity of fusion inhibitors by introducing specific mutations that alter envelope conformation and receptor usage.

PRESENTING AUTHOR: M Kearney

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