Hili Inhibits HIV Replication in Activated T Cells

Area of Science:

• Molecular Biology
• Virology
• Immunology

Background:

• Piwil proteins are known to restrict mobile genetic elements in the germ line.
• Human Piwil 2 (Hili) is expressed in various cell lines.
• CD4+ T cells are the primary targets for HIV replication.

Purpose of the Study:

• To investigate the role of human Piwil 2 (Hili) in inhibiting HIV replication.
• To understand the mechanism by which Hili affects viral replication.
• To explore Hili's function in activated T cells and its impact on other mobile genetic elements.

Main Methods:

• Assessed Hili expression in resting and activated CD4+ T cells.
• Depleted Hili in cells and measured viral protein and particle levels.
• Investigated Hili's interaction with tRNA and targeted tRNAArg(UCU) with antisense oligonucleotides.
• Examined Hili's effect on intracisternal A particle (IAP) retrotransposition.

Main Results:

• Hili expression is induced upon T cell activation and inhibits HIV replication in CD4+ T cells.
• Hili depletion leads to increased viral loads.
• Hili binds to specific tRNA species, including rare ones with codons overrepresented in the HIV genome.
• Targeting tRNAArg(UCU) mimics Hili's antiviral effect.
• Hili also inhibits the retrotransposition of endogenous IAPs.

Conclusions:

• Human Piwil 2 (Hili) acts as a host antiviral factor against HIV and endogenous retroelements.
• Hili's mechanism involves binding to specific tRNAs, potentially interfering with viral replication and retrotransposition.
• Hili represents a novel intracellular defense mechanism against both exogenous and endogenous mobile genetic elements.