Substitutions T200A and E227A in the hemagglutinin of pandemic 2009 influenza A virus increase lethality but decrease...

Area of Science:

• Virology
• Molecular Biology
• Pathogenesis

Background:

• The 2009 pandemic influenza virus (H1N1) caused a global health crisis.
• Understanding viral evolution and adaptation is crucial for pandemic preparedness.
• The hemagglutinin (HA) protein plays a key role in influenza virus entry and infectivity.

Purpose of the Study:

• To investigate the impact of specific swine influenza virus-like substitutions (T200A and E227A) in the HA of the 2009 pandemic influenza virus.
• To determine how these HA mutations affect viral pathogenesis and transmission.
• To identify potential adaptive changes in swine-origin influenza viruses.

Main Methods:

• Site-directed mutagenesis was used to introduce T200A and E227A substitutions into the HA gene of the 2009 pandemic influenza virus.
• Viral replication was assessed in mammalian cell cultures.
• Disease severity in infected mice was measured by weight loss and lethality.
• Transmission efficiency was evaluated in a ferret model.

Main Results:

• The T200A and E227A substitutions significantly increased viral replication in mammalian cells.
• Infected mice exhibited enhanced disease, characterized by greater weight loss and increased lethality.
• Co-occurrence of both substitutions led to decreased transmission in ferrets.
• Amino acids 200T and 227E appear to be adaptive changes in swine-origin influenza viruses.

Conclusions:

• Swine influenza virus-like substitutions T200A and E227A in the HA alter the pathogenesis and transmission of the 2009 pandemic influenza virus.
• These mutations are associated with increased viral replication and virulence in mammals.
• The findings suggest a trade-off between pathogenesis and transmission, with these amino acids potentially representing adaptive changes for swine-origin influenza viruses.