Anti-Influenza A Virus Activities of Type I/III Interferons-Induced Mx1 GTPases from Different Mammalian Species.

This research article studies the antiviral effect of certain proteins named Mx against the influenza A virus. The research found that specific residues in a part of the Mx protein, named the “loop L4”, are critical for the antiviral function of these proteins in different mammalian species.

Understanding Anti-Influenza activities of Mx Proteins

• The research primarily focuses on proteins named Mx, which are induced by Type I/III interferons in mammals. These interferons are part of the body’s innate defense mechanism against viruses.
• The focus is on influenza A viruses and how Mx proteins of different species play a key role in defense against these viruses.
• The researchers believe that such an antiviral protein (Mx) should have a specific platform for recognizing the viruses it defends against. They aim to identify such a structure in human MxA proteins.

The Evolution-Guided Approach

• Researchers use an evolution-guided approach to identify viral recognition platform in human MxA. This is based on the concept of an antagonistic arms race between MxA and its viral targets and the genomic signature it has left in primate genomes.
• The study reveals that “loop L4”, a surface-exposed structure that protrudes from the compact structure of the MxA stalk, undergoes recurrent positive selection.
• The authors then apply this reasoning to Mx1 proteins, expecting that loop L4 must be a recognition platform for influenza viruses across different species.

Comparative Analysis and Key Findings

• The anti-influenza activity of Mx1 proteins from five different mammalian species was examined by observing the number of viral nucleoprotein-positive cells after infection.
• This comparative analysis shows a substantial reduction in virus nucleoprotein-positive cells among populations of cells expressing equine, bubaline, porcine, and bovine Mx1 proteins when compared to Mx-negative cells. This suggests strong anti-influenza activity of Mx1 proteins.
• The researchers identify aromatic residue at positions 561 or 562 in the L4 loop as a critical determinant of the anti-influenza function and/or specificity of mammalian Mx1 proteins.