Deep mutational scanning identifies sites in influenza nucleoprotein that affect viral inhibition by MxA

Area of Science:

• Virology
• Immunology
• Molecular Biology

Background:

• The innate immune factor MxA inhibits influenza virus replication.
• Human influenza strains exhibit greater MxA resistance than avian strains, linked to viral nucleoprotein (NP) variations.
• Previous studies identified resistance-conferring NP mutations from documented zoonotic transmissions.

Purpose of the Study:

• To systematically identify all single amino-acid mutations in influenza NP that affect MxA sensitivity using deep mutational scanning.
• To uncover novel sites in NP influencing MxA resistance beyond those identified through historical adaptation studies.

Main Methods:

• Deep mutational scanning of all single amino-acid mutations in influenza NP.
• Quantification of MxA sensitivity in the context of replication-competent virus.
• Comparison of identified mutations with those from historical influenza adaptations.

Main Results:

• Identified new NP sites where mutations confer MxA resistance.
• Re-identified known mutations associated with increased MxA resistance during human adaptation.
• Found that highly conserved sites in NP are critical for MxA resistance and cluster in MxA recognition regions.

Conclusions:

• This study systematically maps NP sites affecting MxA sensitivity, revealing conserved regions crucial for resistance.
• Deep mutational scanning provides a powerful strategy for identifying host-factor interaction sites in viral proteins.
• Findings enhance understanding of influenza virus adaptation and host immune evasion mechanisms.