JM-2763

We describe the development of chimeric virus technology (CVT) for human immunodeficiency virus (HIV) type 1 (HIV-1) env genes gp120 , gp41 , and gp160 for evaluation of the susceptibilities of HIV to entry inhibitors. This env CVT allows the recombination of env sequences derived from different strains into a proviral wild-type HIV-1 clone (clone NL4.3) from which the corresponding env gene has been deleted. An HIV-1 strain (strain NL4.3) resistant to the fusion inhibitor T20 (strain NL4.3/T20) was selected in vitro in the presence of T20. AMD3100-resistant strain NL3.4 (strain NL4.3/AMD3100) was previously selected by De Vreese et al. (K. De Vreese et al., J. Virol. 70:689-696, 1996). NL4.3/AMD3100 contains several mutations in its gp120 gene (De Vreese et al., J. Virol. 70:689-696, 1996), whereas NL4.3/T20 has mutations in both gp120 and gp41 . Phenotypic analysis revealed that NL4.3/AMD3100 lost its susceptibility to dextran sulfate, AMD3100, AMD2763, T134, and T140 but not its susceptibility to T20, whereas NL4.3/T20 lost its susceptibility only to the inhibitory effect of T20. The recombination of gp120 of NL4.3/AMD3100 and gp41 of NL4.3/T20 or recombination of the gp160 genes of both strains into a wild-type background reproduced the phenotypic (cross-)resistance profiles of the corresponding strains selected in vitro. These data imply that mutations in gp120 alone are sufficient to reproduce the resistance profile of NL4.3/AMD3100. The same can be said for gp41 in relation to NL4.3/T20. In conclusion, we demonstrate the use of env CVT as a research tool in the delineation of the region important for the phenotypic (cross-)resistance of HIV strains to entry inhibitors. In addition, we obtained a proof of principle that env CVT can become a helpful diagnostic tool in assessments of the phenotypic resistance of clinical HIV isolates to HIV entry inhibitors.

Bicyclams are low-molecular-weight anti-human immunodeficiency virus (HIV) agents that have been shown to act as potent and selective CXC chemokine receptor 4 (CXCR4) antagonists. Here, we demonstrate that bicyclams are potent inhibitors of feline immunodeficiency virus (FIV) replication when evaluated in Crandell feline kidney (CRFK) cells. With a series of bicyclam derivatives, 50% inhibitory concentrations (IC 50 s) against FIV were obtained in this cell system that were comparable to those obtained for HIV-1 IIIB replication in the human CD4 + MT-4 T-cell line. The bicyclams were also able to block FIV replication in feline thymocytes, albeit at higher concentrations than in the CRFK cells. The prototype bicyclam AMD3100, 1-1′-[1,4-phenylene-bis(methylene)]-bis(1,4,8,11-tetraazacyclotetradecane), was only fourfold less active in feline thymocytes (IC 50 , 62 ng/ml) than in CRFK cells (IC 50 , 14 ng/ml). AMD2763, 1,1′-propylene-bis(1,4,8,11-tetraazacyclotetradecane), which is a less potent CXCR4 antagonist, was virtually inactive against FIV in feline thymocytes (IC 50 , >66.5 μg/ml), while it was clearly active in CRFK cells (IC 50 , 0.9 μg/ml). The CXC chemokine stromal-cell-derived factor 1α had anti-FIV activity in CRFK cells (IC 50 , 200 ng/ml) but not in feline thymocytes (IC 50 , >2.5 μg/ml). When primary FIV isolates were evaluated for their drug susceptibility in feline thymocytes, the bicyclams AMD3100 and its Zn 2+ complex, AMD3479, inhibited all six primary isolates at equal potency. The marked susceptibility of FIV to the bicyclams suggests that FIV predominantly uses feline CXCR4 for entering its target cells.