Mechanism of HIV-1 Virolytic Inactivation by Env-Targeting Peptide Triazole Thiols

HIV-1 Env is the only virus-specific protein on the virion surface and is essential for cell receptor interactions and subsequent virus-cell fusion, therefore it is an important therapeutic target for inhibiting the initial steps leading to host cell infection. Peptide triazoles (PTs) are novel antagonistic entry inhibitors of HIV-1 Env, which block gp120 binding to CD4 and co-receptor on the host cell. We have determined that a subclass of PTs that contain a C-terminal cysteine, peptide triazole thiols (PTTs), cause irreversible viral inactivation and lysis. We determined that the thiol group is required for lytic activity and hypothesize that PTT-induced lysis requires disulfide exchange between Env and PTT. To understand the lytic mechanism of action of PTTs, we performed structure activity relationship studies and found a disproportionate loss of lysis activity vs binding upon linker truncation, indicating that a minimum length is required for lysis. Molecular dynamics simulation displayed the trajectory of the peptide SH group and suggested that it could interfere with conserved disulfides clustered proximal to the CD4 binding site in gp120, which was validated by Gp120 protein ligand and mutational analysis. Additionally, viral inhibition assays using sulfhydryl blocking and reducing agents inhibited and enhanced p24 release induced by PTT’s, respectively. Our data suggest that PTTs hijack the native HIV entry process by triggering disulfide exchange between gp120 and the peptide group thiol, leading to molecular transformations of the HIV-1 trimer. The specificity and potency of the peptide triazole thiols as virolytic agents argue for their potential as drug leads for therapeutic approaches to suppress the spread of AIDS.Ph.D., Biochemistry -- Drexel University, 201