Getting the flu is not fun. Generally, young, strong and healthy people spend a week in bed, but are then over it. For others, however, the viral infection is just the beginning.

Fighting off a respiratory virus can weaken the body, putting it at risk for a secondary infection from another virus or bacteria. These secondary infections, like pneumonia, are the leading cause of death during flu pandemics.

Our group has discovered that viruses in the lung trigger a very predictable sequence of events that affect vulnerability to these secondary bacterial infections.

We found that the body’s response to a secondary infection changes over time during flu, and that these responses are initially triggered by how the immune system recognizes the outside shell of a virus, called the viral capsid.

We also found that capsids of viruses other than flu can trigger the same sequence of events, making us either more or less likely to develop secondary pneumonias.

The Francis Family Foundation is providing funding for us to understand exactly how viral capsids are recognized by our immune system and how the initial immune response to a virus makes secondary infection either less or more likely to develop.

Our experiments are focusing on:

• how the immune cells recognize viruses;
• what happens in the body after a virus is recognized;
• how long the response takes; and,
• the cell signaling that drives these processes.

The results of this work will help make better vaccines for patients facing life-threatening pneumonias. It may also contribute to the development of bacterial therapies, by improving our understanding of how the body differentiates between viruses and bacteria.