397-T. Genotypic and Phenotypic Analysis of <i>in Vitro</i> Generated HIV-1 Escape Isolates to the CCR5 Antagonist SCH-C

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

397-T.

Genotypic and Phenotypic Analysis of in Vitro Generated HIV-1 Escape Isolates to the CCR5 Antagonist SCH-C
J. Riley*, L. Wojcik, S. Xu, and J. Strizki
Schering-Plough Res. Inst., Kenilworth, NJ

Background: SCH-C represents a new class of CCR5 antagonists that has potent antiviral activity against HIV-1 infection. This molecule binds to CCR5 and blocks the entry of HIV-1 isolates that uses this receptor for infection.
Method: To investigate the potential mechanism of viral resistance to this CCR5 antagonist we generated escape variants by infection of peripheral blood mononuclear cells (PBMCs) with different HIV-1 strains followed by continuous passaging in the presence of increasing increments of SCH-C.
Results: After 19 weeks of passage, variants with reduced sensitivity to the compound emerged. Characterization of these viruses showed no switch to other chemokine receptors including CXCR4. Further analyses of these adapted variants showed a high level of cross-resistance with receptor ligands RANTES, MIP1alpha, and a neutralizing CCR5 monoclonal antibody, 2D7. Genotypic analyses of the viral isolates showed a marked degree of sequence variation in gp120 amino acid residues in viruses treated with the compound. To determine the stability of the resistant mutants in the absence of selection, drug was removed and the cultures were passaged in the absence of drug selection. Drug resistant viruses were still detected following 14 weeks of passage in the absence of drug, however by 20 weeks the cultures became sensitive to SCH-C.
Conclusion: From these analyses we have determined that escape viruses to SCH-C continue to use CCR5 as the co-receptor in HIV-1 infection. Additionally, these variants showed high levels of cross-resistance to other receptor ligands and to CCR5 monoclonal antibody 2D7. Genetic analyses showed some sequence diversification in the envelope gene. Further work will be required to determine the effect amino acid substitutions on viral co-receptor usage, viral fitness and drug potency. Finally, removal of selective pressure resulted in gradual reversal to a drug sensitive phenotype suggesting that the mutant virus maybe less fit compared with the wild type.

Š2002 9^th Conference on Retroviruses and Opportunistic Infections