561-T. Impact of Gag Sequence Polymorphisms on HIV-1 Resistance to Protease Inhibitors

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Session 75 Poster Session
Resistance to Antiretroviral Chemotherapeutic Agents
Session Time: 4:30-6:30 pm
Room 4E-F

561-T.

Impact of Gag Sequence Polymorphisms on HIV-1 Resistance to Protease Inhibitors
L. Carron de la Carrière, F. Mammano, and F. Clavel
INSERM U552, Hosp. Bichat, Paris, France

Background: Mutations in Gag cleavage sites are known to substantially affect HIV susceptibility to protease inhibitors (PI) in the context of protease (PR) resistance mutations. Little is known, however, on the impact of natural Gag polymorphisms and the role of Gag mutations outside of the cleavage sites in PI resistance.
Methods: We constructed chimeric viruses carrying Gag sequences from PI-naive or PI-experienced viruses in association with either wild-type (WT) or mutant PR. PI susceptibility and replicative capacity of the reconstructed viruses were tested in a single-cycle assay.
Results: We first identified a virus (210), in which the Gag sequence promoted a marked hypersusceptibility to PIs. The ritonavir IC90 of WT PR was decreased 8-fold by 210 Gag relative to NL4-3 Gag (17nM vs 137nM), and that of a PR with 3 mutations (I54V, L63P, V82A) was decreased 5-fold (194nM vs 979nM). Similar observations were made with indinavir. Hypersusceptibility was not related to reduced fitness, since insertion the 210 Gag sequence next to either WT or resistant PR did not significantly modify viral replicative capacity. To extend this observation, a larger series of chimeric viruses was reconstructed by rapid homologous recombination of NL4-3 with plasma–derived Gag sequences from PI-naïve or PI-experienced patients. Again, we observed that different Gag sequences could substantially modify (up to 3-fold) PI susceptibility of WT or mutated PR. Interestingly, the level of susceptibility observed with Gag sequences from PI-experienced patients (only one of which had a A431V Gag cleavage site mutation) was significantly higher than that observed with treatment-naïve patients, suggesting that changes in Gag outside of the cleavage sites could be associated with a decrease in PI susceptibility. Genetic analysis of these two groups of Gag sequences is under way. Finally, we observed that insertion of Gag sequences from non-B subtypes, most notably from subtypes F and G, produced a marked increase in PI susceptibility.
Conclusions: Sequence differences in Gag, located outside of the cleavage sites, can affect HIV-1 susceptibility to PI.