Comparative mutational analyses of influenza A viruses

Area of Science:

• Virology
• Molecular Biology
• Bioinformatics

Background:

• RNA viral diversity is driven by error-prone RNA-dependent RNA polymerase (RdRP) and selective pressures.
• Assessing spontaneous mutation frequency in RdRPs of influenza A viruses (IAV) with wide host ranges is challenging due to confounding selective pressures.

Purpose of the Study:

• To compare the spontaneous mutational frequencies and identify mutable motifs in RdRPs from human seasonal and H5N1 influenza A viruses.
• To establish a bioinformatics platform for analyzing RNA virus mutation spectra.

Main Methods:

• Utilized a mini-genome system with a firefly luciferase reporter to analyze RdRPs from human seasonal (Wuhan) and H5N1 (VN1203) IAV.
• Employed high-fidelity reverse transcriptase to generate high-quality mutational spectra for comparative analysis.
• Confirmed findings using recombinant A/Puerto Rico/8/34 (PR8) viruses expressing RdRPs from Wuhan and VN1203 strains.

Main Results:

• Observed correlated mutational spectra between the two RdRPs (τ correlation P < 0.0001).
• Found comparable spontaneous mutational frequencies: H3N2 (5.8 ± 0.9) and H5N1 (6.0 ± 0.5).
• Identified a highly mutable motif "(A)AAG" common to both Wuhan and VN1203 RdRPs.

Conclusions:

• Influenza A virus RdRPs from different subtypes exhibit similar spontaneous mutation rates and a conserved mutable motif.
• The developed bioinformatics approach provides a robust platform for analyzing RNA virus mutation spectra and understanding viral evolution.