Structural Domains of the Herpes Simplex Type 1 gD Protein that Restrict HIV-1 Particle Infectivity

Area of Science:

• Virology
• Molecular Biology
• Immunology

Background:

• Herpes simplex virus type 1 (HSV-1) glycoprotein D (gD) was previously shown to restrict human immunodeficiency virus type 1 (HIV-1) particle infectivity.
• This restriction involves the incorporation of HSV-1 gD and exclusion of HIV-1 envelope glycoproteins (gp120/gp41) from nascent viral particles.

Purpose of the Study:

• To identify the structural domains of HSV-1 gD responsible for restricting HIV-1 infectivity.
• To investigate the relationship between gD's cell surface expression, its incorporation into HIV-1 particles, and the resulting restriction of infectivity.

Main Methods:

• Generation of HSV-1 gD deletion mutants and chimeric proteins with the non-restrictive HSV-1 glycoprotein B (gB).
• Analysis of chimeric proteins to assess the impact of specific domains (cytoplasmic tail domain - CTD, transmembrane domain - TMD) on gD function.
• Evaluation of cell surface expression, incorporation into HIV-1 particles, and restriction of infectious HIV-1 release.
• Investigation of gD localization within detergent-resistant membranes (DRMs) and co-localization with raft markers.

Main Results:

• Deletion of gD's CTD or replacement of its TMD with gB's TMD only slightly reduced restriction activity.
• Replacing gD's CTD with gB's CTD significantly decreased cell surface expression, HIV-1 particle incorporation, and restriction efficiency.
• Chimeric proteins with gB's CTD showed reduced surface expression and HIV-1 restriction, while removal of gB's CTD or replacement with gD's CTD enhanced both.
• HSV-1 gD alone fractionated into DRMs and co-localized with the GM1 raft marker, suggesting a mechanism for its incorporation into budding virus particles.

Conclusions:

• HSV-1 gD surface expression is a critical factor for restricting HIV-1 particle infectivity.
• The cytoplasmic tail domain (CTD) of gD plays a significant role in its incorporation into HIV-1 particles and subsequent restriction.
• The transmembrane domain (TMD) of gB can influence protein transport and incorporation into HIV-1.
• Intrinsic properties of gD, potentially related to its membrane association, also contribute to the observed restriction of HIV-1 infectivity.