Enhanced human receptor binding by H5 haemagglutinins

Area of Science:

• Virology
• Molecular Biology
• Structural Biology

Background:

• Human H5N1 influenza virus infections are a concern.
• Mutations in H5N1 viruses can alter receptor binding avidity.

Purpose of the Study:

• To compare receptor binding properties of H5N1 mutants with wild-type viruses.
• To determine the structures of H5N1 haemagglutinins in complex with receptor analogues.

Main Methods:

• Isolation and characterization of mutant H5N1 influenza viruses from humans.
• Analysis of receptor binding avidity to human and avian receptors.
• Determination of haemagglutinin structures using X-ray crystallography.

Main Results:

• Mutants from Vietnam acquired basic residues, increasing human receptor avidity but decreasing avian receptor avidity.
• An Egyptian double mutant (Δ133/Ile155Thr) enhanced human receptor avidity while maintaining avian receptor avidity.
• None of the studied mutants exhibited a preference for human receptors over avian receptors.

Conclusions:

• Mutant H5N1 viruses can exhibit altered receptor binding profiles, with some adapting to human receptors.
• These mutants may represent intermediate stages in the evolution of H5N1 viruses with broader host potential.
• Further research is needed to understand the implications for H5N1 transmission and pathogenicity.