XI International HIV Drug Resistance Workshop: Basic Principles and Clinical Implications Seville, Spain, 2–5 July 2002

BACKGROUND: The nucleocapsid (NC) protein of HIV-1 contains two zinc fingers with non-classical Cys-X2-Cys-X4-His-X4-Cys (CCHC) sequences. These zinc fingers are attractive as antiviral targets because they are essential for key events during viral replication and they are highly conserved. Studies were undertaken to determine if representative compounds could selectively target the viral NC zinc fingers and inhibit strains of HIV-1 resistant to classical drugs. Moreover, extensive in vitro resistance induction studies were performed in an attempt to identify mutational escape strains of HIV-1.

METHODS: Antiviral activity was evaluated by classic CPE assays, biochemical assays were utilized for other viral and cellular proteins, and immunoblotting analysis was applied to evaluate the effect of NC inhibitors on viral proteins.

RESULTS: NC inhibitors demonstrated equivalent in vitro antiviral potency against HIV-1, HIV-2 and SIV, each of which contains CCHC zinc fingers. In contrast, a series of other viruses (not retroviruses) were unaffected by the NC inhibitors. Mechanism of action studies demonstrated a direct action on the HIV-1 NC protein zinc fingers, but there was no inhibitory action on a panel of cellular zinc finger-containing proteins or on HIV-1 virus attachment and fusion events, on the reverse transcriptase, integrase or protease enzymes, or on virus gene expression. NC inhibitors modified zinc fingers of the HIV-1 Gag precursor polyproteins and disrupted normal processing of those precursors. Equivalent disruption of Gag polyproteins was observed in cell cultures transfected with a proviral DNA containing mutated zinc fingers. Finally, a series of attempts to induce in vitro resistance to the NC inhibitors has yet to yield HIV-1 escape mutants demonstrating loss of antiviral sensitivity.

CONCLUSION: (1) The data are consistent with an antiviral action elicited by selective targeting of the HIV NC zinc fingers. (2) NC inhibitors are active against HIV-1 strains resistant to other drugs. (3) In vitro induction of virus strains resistant to NC inhibitors has thus far proved unsuccessful, as predicted from the essential and conserved nature of NC zinc fingers. (4) NC zinc finger inhibitors may be a valuable addition to current therapies and may help curb the rapid emergence of viral resistance.

PRESENTING AUTHOR: WG Rice

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2002-07-02
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