Identifying changes in selective constraints: host shifts in influenza

Area of Science:

• Virology
• Genomics
• Evolutionary Biology

Background:

• Influenza A's natural reservoir is waterfowl, with viruses typically not adapted for human transmission.
• Reassortment or host shifts can introduce avian influenza A viruses into humans, potentially causing pandemics.
• Understanding mutations facilitating avian-to-human transmission is crucial for pandemic prediction and control.

Purpose of the Study:

• To develop and apply a novel phylogenetic approach for identifying mutations enabling avian influenza A virus adaptation to the human host.
• To pinpoint specific amino acid sites under different selection pressures in avian versus human influenza A viruses.

Main Methods:

• Utilized a sitewise non-homogeneous phylogenetic model.
• Accounted for differences in amino acid equilibrium frequencies across hosts and locations.
• Analyzed genetic data from avian and human influenza A viruses.

Main Results:

• Identified 172 amino acid sites with strong support for different selection constraints between human and avian viruses.
• Identified 518 amino acid sites with moderate support for distinct selection pressures.
• Provided a resource of critical sites for experimental virologists studying avian flu adaptation.

Conclusions:

• The novel phylogenetic model effectively identifies key mutations for avian influenza A virus host shifts.
• The identified sites are valuable for predicting the pandemic potential of influenza strains.
• This method has broad applications for studying evolutionary changes in selective constraints when temporal data is available.