Different selection patterns of resistance and cross-resistance to HIV-1 agents targeting CCR5

Identification of CCR5 as an antiretroviral target led to the development of several CCR5 antagonists in clinical trials and the approval of maraviroc. Evaluating the mechanism of drug resistance to CCR5 agents may have implications in the clinical development of this class of agents. We have analysed the resistance profile of two R5 HIV-1 strains [BaL and a clinical isolate (CI)] after long-term passage in cell culture in the presence of TAK-779, the first developed non-peptidic small molecule targeting CCR5. Genotypic and phenotypic tests were used to evaluate the resistance of virus isolated from cell culture in the presence of the CCR5 inhibitor TAK-779. Mutations conferring resistance appeared in the gp120 sequence but were not confined to the V3 loop region, and both strains had a different mutation pattern. Recombination of the env gene of the BaL-derived resistant virus into the HIV-1 HXB2 wild-type backbone conferred resistance to TAK-779 and cross-resistance to maraviroc, with 63- and 11-fold changes in their EC50 (50% effective concentration), respectively, together with an apparent reduction of the maximal plateau inhibition (MPI) of TAK-779 but not of maraviroc. Conversely, the resistant CI viruses showed an similar to 50% reduction in MPI for both TAK-779 and maraviroc. We confirm that different pathways to the generation of CCR5 drug resistance/cross-resistance may occur that strongly depend on cell culture conditions, CCR5 availability and the genetic background of the HIV strain. Our study provides complementary information to understand the complexity of resistance to CCR5 antagonists.