RESUMEN
Infection by HIV-1 most often results from the successful transmission and propagation of a single virus variant, termed the transmitted/founder (T/F) virus. Here, we compared the attachment and entry properties of envelope (Env) glycoproteins from T/F and chronic control (CC) viruses. Using a panel of 40 T/F and 47 CC Envs, all derived by single genome amplification, we found that 52% of clade C and B CC Envs exhibited partial resistance to the CCR5 antagonist maraviroc (MVC) on cells expressing high levels of CCR5, while only 15% of T/F Envs exhibited this same property. Moreover, subtle differences in the magnitude with which MVC inhibited infection on cells expressing low levels of CCR5, including primary CD4(+) T cells, were highly predictive of MVC resistance when CCR5 expression levels were high. These results are consistent with previous observations showing a greater sensitivity of T/F Envs to MVC inhibition on cells expressing very high levels of CCR5 and indicate that CC Envs are often capable of recognizing MVC-bound CCR5, albeit inefficiently on cells expressing physiologic levels of CCR5. When CCR5 expression levels are high, this phenotype becomes readily detectable. The utilization of drug-bound CCR5 conformations by many CC Envs was seen with other CCR5 antagonists, with replication-competent viruses, and did not obviously correlate with other phenotypic traits. The striking ability of clade C and B CC Envs to use MVC-bound CCR5 relative to T/F Envs argues that the more promiscuous use of CCR5 by these Env proteins is selected against at the level of virus transmission and is selected for during chronic infection.