Improved HSV-1 amplicon packaging using virion host shutoff mutants lacking mRNAse activity

Area of Science:

• Neuroscience
• Molecular Biology
• Virology

Background:

• Herpes simplex virus type 1 (HSV-1) vectors are valuable for gene delivery to the central nervous system due to their capacity and neurotropism.
• Vector toxicity, particularly from the virion host shutoff (vhs) protein, limits the clinical application of HSV-1 vectors.
• The vhs protein's mRNAse activity causes translational arrest, contributing to cellular toxicity.

Purpose of the Study:

• To investigate the role of the vhs protein (encoded by the U(L)41 gene) in HSV-1 amplicon packaging.
• To determine if vhs influences the survival of neurons after transduction with HSV-1 vectors.
• To explore strategies for reducing HSV-1 vector toxicity while maintaining efficacy.

Main Methods:

• Utilized HSV-1 viruses with deletions in the U(L)41 open reading frame.
• Assessed the impact of U(L)41 deletions on amplicon packaging efficiency.
• Evaluated vector-induced toxicity in dissociated cortical neurons.
• Tested mRNAse-inactive point mutants of vhs to partially restore function.

Main Results:

• Deletion of U(L)41 significantly reduced amplicon yield but also decreased vector toxicity.
• Partial restoration of vhs function using point mutants improved amplicon titers.
• mRNAse-inactive vhs mutants enhanced titers without causing the toxicity associated with wild-type HSV-1.

Conclusions:

• The vhs protein is a key contributor to HSV-1 vector toxicity.
• Modifying vhs function offers a viable strategy to improve the safety profile of HSV-1 gene delivery vectors.
• Targeting vhs can enhance the therapeutic potential of HSV-1 vectors for central nervous system gene therapy.