pH & Influenza

Influenza is a viral infection of the respiratory tract that causes an estimated 41,000 deaths in the United States each year. The pH or acidity of its environment is important to the function and stability of the virus.

Features

• The influenza virus is an RNA virus (its genetic information is encoded in RNA rather than DNA). The viral genome is enclosed in a protein shell called a capsid, surrounded by an envelope made up of oily molecules, like the molecules that make up cell membranes.

Function

• Once the virus is taken up by a cell, it becomes enclosed in a membrane-bound sac called an endosome. The change in pH that takes place while the virus is in the endosome causes changes in the virus that help it to escape the endosome so it can take over the cell.

Effects

• If the virus is treated with an acidic solution (low pH) before it infects cells, the acidic solution will change the shape of the proteins the virus uses to infect cells and the virus will become inactive. Influenza viruses are inactivated by a pH of 5.2 or below.

Considerations

• The virus cannot tolerate low pH before it has infected the cell; it may need the change in pH that takes place once it's inside the endosome, however, to escape the endosome and infect the cell. The virus does not function well in a very acidic or basic solution (high or low pH).

Significance

• The pH is important for the influenza virus because pH can affect protein folding and aggregation. Acidic or basic pH can denature proteins, like the proteins the virus uses to infect cells, and thereby inactivate the virus.