How Flu Evolves to Escape Immunity

Influenza haemagglutinin

Influenza haemagglutinin (Photo credit: AJC1)

Kelley Monaghan (12:00 Micro) found this article from Science Daily detailing one mechanism as to how influenza changes from year to year, via the process of antigenic drift.  Here is Kelley’s summary:

From research published recently in the journal Science, Scientists have discovered the reason behind the flu’s immunity to vaccines. They previously knew that this immunity was due to a substitution in a single amino acid, believing that this occurred on 130 places on its surface. But, the recent discovery proved that the single amino acid substitution happens at seven places instead of 130 places. This discovery could help us make more efficient flu vaccines in the future, due to the more thorough understanding of the flu viruses’ evolution. From University of Cambridge, Professor Derek Smith believe that scientists would be able to foretell what the evolution of the flu would be, and put that knowledge of the evolution into the vaccine to make them one step better than our current vaccines.

The flu vaccine makes it possible for our immune system to easily make antibodies when infected with the flu that kill the virus. That is what the flu vaccine allows our body to do; by introducing inactivated flu it teaches our immune system how to fight the three types of the flu virus. This vaccine is completely efficient until the virus evolves, leaving the vaccine now useless. The immune system doesn’t know how to fight the new evolved virus, because this new strain of the flu virus is immune to the old vaccine. Vaccines must be updated due to the constant evolving virus, and because of this twice a year the World Health Organization meets to update the vaccines to address the new stains.

Researchers conducted tests from viruses they created to see what caused the development of new strains. They did this by creating viruses that had both different amino acid substitutions and combinations and recorded this then tested to see which substitutions and combinations ended up leading to the development of the new strain. This experiment showed that it only took one amino acid substitution for the flu to form new strains. This shocked many scientists because prior to this experiment, they believed for the flu to develop new strains it had to undergo at least the substitution of four amino acids. In addition, they discovered that the receptor-binding site was close to where the changes to the one amino acid happened; the change in the one amino acid happening on the surface at seven spots. The receptor binging site is extremely important to the flu virus because that is where attachment to the host occurs. In conclusion, this recent discovery could be extremely beneficial in the way we make our vaccines against the flu virus. Because understanding the flu virus’s evolution we can make more efficient vaccines.

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About ycpmicro

My name is David Singleton, and I am an Associate Professor of Microbiology at York College of Pennsylvania. My main course is BIO230, a course taken by allied-health students at YCP. Views on this site are my own.

Posted on December 5, 2013, in Guest Post. Bookmark the permalink. Comments Off on How Flu Evolves to Escape Immunity.

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