Multiple Pathways To Avoid Beta Interferon Sensitivity of HIV-1 by Mutations in Capsid

Area of Science:

• Virology
• Immunology
• Molecular Biology

Background:

• Type I interferons (IFNs) suppress HIV-1 replication by upregulating IFN-stimulated genes (ISGs).
• The HIV-1 capsid protein (CA) influences viral sensitivity to IFNs, but mechanisms of adaptation are unclear.
• Previous studies linked IFN sensitivity to CA interactions with host factors like CPSF6 and CypA.

Purpose of the Study:

• To investigate how HIV-1 evolves resistance to IFN-β-mediated restriction targeting the viral capsid.
• To determine the role of CA mutations and host factor interactions in IFN resistance.
• To elucidate the distinct mechanisms by which HIV-1 evades IFN-β blocks.

Main Methods:

• Experimental evolution of an IFN-β-hypersensitive HIV-1 CA mutant (RGDA/Q112D virus) in IFN-β-treated cells.
• Isolation and characterization of IFN-β-resistant variants with specific CA mutations (Q4R or G94D/G116R).
• Assays to assess CA binding to host factors (MxB, CPSF6, CypA) and viral kinetics (reverse transcription, uncoating).

Main Results:

• IFN-β-resistant HIV-1 variants emerged with Q4R or G94D/G116R mutations in CA.
• These mutations altered CA binding to MxB, CPSF6, and CypA, but not solely due to known factor interactions.
• The Q4R mutation accelerated reverse transcription and uncoating, while G94D/G116R affected reverse transcription in an IFN-β-dependent manner, suggesting unknown host factor involvement.

Conclusions:

• HIV-1 employs multiple, known host factor-independent pathways to overcome IFN-β restriction.
• Altering CA sequences and subsequent biological properties (e.g., reverse transcription, uncoating kinetics) are key evasion strategies.
• The findings reveal novel mechanisms of viral adaptation to innate immune responses.