399-T. Role of Co-Receptor Inhibitors in Blocking HIV-1 Primary Isolates <i>in Vitro</i>

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Session 58 Poster Session
Entry Inhibitors
Session Time: 4:30-6:30 pm
Room 4E-F

399-T.

Role of Co-Receptor Inhibitors in Blocking HIV-1 Primary Isolates in Vitro
P. Citterio*¹, E. Bulgheroni¹, F. Croce¹, M. Lo Cicero¹, P. Bagnarelli², M. Galli¹, and S. Rusconi¹
¹Univ. of Milan and ²Univ. of Ancona, Italy

Background: Different strategies in blocking HIV entry are being evaluated either by targeting one of the cellular receptors, CD4 or co-receptors, or the envelope proteins. The majority of available compounds interfere with the binding of gp120 with the co-receptor. These molecules are chemokine analogues, which interfere in binding with the corresponding cellular receptor thus preventing the entry of HIV-1 in the target cells.
Methods: In this set of experiments we studied the effect on HIV-1 replication of several compounds directed against HIV-1 co-receptors in infections mediated by primary HIV-1 infection (PHI) isolates either from the United States or Italy. All viruses were characterized for their tropism in CCR5- and CXCR4-transformed cell lines and sequenced in their env V3 region. We tested PA14, a monoclonal antibody specifically targeted to CCR5, TAK-779, a small anilide derivative directed against CCR5, and AMD-3100, a bicyclam compound active in X4-tropic viruses. We determined the 50% inhibitory concentration (IC50) according to an ACTG-modified protocol in PBMC. Then, we conducted experiments utilizing IC95 single drugs or combined drugs against infections with RM (R5) or DK (X4) viruses or against mixed infection (1:1).
Results: PA14 inhibited PHI R5-tropic isolates at nanomolar concentrations, whereas it did not show any activity in DK and 14aPre (X4 clinical isolate) infections. Moreover, PA14 inhibited several viruses derived from patients with a mutagenized R5 V3-loop in a dose-dependent manner (IC50 range 0.074-0.093 µM). TAK-779 was active vs RM and MB isolates: IC50 0.0013 and 0.0014 µM, respectively; AMD-3100 was active vs DK and 14aPre isolates: IC50 0.005 and 0.041 µM, respectively, and BA 0.097 µM. Combination of TAK-779 and AMD-3100 inhibited dual infections with RM and DK (85%), whereas single drugs suppressed dual infections less efficiently (30.4-78.8%).
Conclusions: Our experiments indicate a selective activity of these attachment/entry inhibitors against HIV-1 clinical isolates with a defined co-receptor use. Of note, the combined activity of R5- and X4-inhibitors may be useful in inhibiting mixed infections.