PF74 Reinforces the HIV-1 Capsid To Impair Reverse Transcription-Induced Uncoating

Area of Science:

• Virology
• Structural Biology
• Biophysics

Background:

• Human immunodeficiency virus type 1 (HIV-1) infection relies on capsid disassembly (uncoating) after cell entry.
• The HIV-1 capsid is crucial for viral reverse transcription and nuclear entry.
• The small molecule PF74 inhibits HIV-1 by binding to the capsid and affecting uncoating, but its mechanism is unclear.

Purpose of the Study:

• To elucidate the mechanism by which PF74 alters HIV-1 capsid stability and influences viral infection.
• To investigate the direct effects of PF74 on the mechanical properties and disassembly of HIV-1 cores.

Main Methods:

• Utilized time-lapse atomic force microscopy (AFM) to observe HIV-1 cores.
• Studied the morphology and physical properties of recombinant capsid assemblies and isolated HIV-1 cores.
• Assessed capsid stability and disassembly dynamics in the presence of varying PF74 concentrations.

Main Results:

• PF74 binding stabilized the HIV-1 capsid lattice in a concentration-dependent manner.
• At 10 μM, PF74 significantly increased capsid mechanical stability, comparable to a hyperstable mutant.
• PF74 inhibited complete capsid disassembly during 24-hour reverse transcription, allowing partial dissociation while maintaining core integrity.

Conclusions:

• PF74 directly stabilizes the HIV-1 capsid lattice, interfering with the uncoating process.
• Capsid stabilization by PF74 permits reverse transcription but disrupts a late stage of uncoating.
• Findings provide direct evidence for PF74's mechanism of action in early HIV-1 infection.