Effect of naturally-occurring gp41 HR1 variations on susceptibility of HIV-1 to fusion inhibitors

BACKGROUND: Sequence variations in the gp41 heptad repeat 1 (HR1) region have been identified in some treatment-naive HIV-1-infected patients but it remained elusive whether they confer resistance to fusion inhibitors. OBJECTIVE: To evaluate whether naturally occurring sequence variations in the HIV-1 group M gp41 HR1 region affect the sensitivity to inhibition by T-20 and T-1249. METHODS: Site-directed mutagenesis was used to generate HIV-1 NL4-3 mutants containing changes in the gp41 HR1 domain which have been previously identified in treatment-naive patients infected with various HIV-1 group M subtypes. HIV-1 variants were produced by transient transfection of 293T cells and used to determine viral infectivity and sensitivity to the fusion inhibitors T-20 and T-1249. RESULTS: Most naturally occurring sequence variations in the HR1 domain did not reduce viral infectivity. Three of the 10 HIV-1 variants analysed containing a single substitution of L33V, which is frequently present in subtype D isolates, or combined changes of L54M/Q56K or L34M/L54M/Q56R showed about fivefold reduced sensitivity to inhibition by T-20. In comparison, none of these HR1 sequence variations conferred resistance to T-1249. CONCLUSION: Some naturally occurring sequence variations in the gp41 HR1 region reduce sensitivity of HIV-1 to inhibition by T-20 but not T-1249.