Generation of replication-proficient influenza virus NS1 point mutants with interferon-hyperinducer phenotype

Area of Science:

• Virology
• Immunology
• Molecular Biology

Background:

• The NS1 protein of influenza A virus is crucial for antagonizing the host interferon response.
• Viruses lacking functional NS1 protein are impaired in IFN-compromised cells but can replicate in cells lacking interferon signaling.

Purpose of the Study:

• To identify specific mutations within the NS1 protein that modulate the interferon response during influenza A virus infection.
• To develop a method for generating replication-proficient, interferon-inducing influenza virus mutants.

Main Methods:

• An unbiased mutagenesis approach was used to create a library of approximately 40,000 point mutants in the NS1 protein.
• Mutant viruses were selected based on their ability to induce interferon (IFN) and green-fluorescent protein (GFP) expression in IFN-competent cells, while replicating in IFN-compromised cells.

Main Results:

• Mutant viruses with altered NS1 proteins were isolated that induced higher IFN levels in competent cells and had reduced capacity to counteract exogenous IFN.
• These mutations were located in previously unreported sites within the RNA-binding domain, effector domain, or linker region of NS1.
• Subtle NS1 alterations reduced its IFN antagonist effectiveness without compromising viral replication capacity.

Conclusions:

• The study identified key NS1 protein positions that regulate the interferon response, demonstrating that minor mutations can significantly impact viral antagonism.
• The developed methodology can generate replication-proficient, IFN-inducing influenza virus mutants with potential applications in vaccine development against various viruses.