Over 50 years ago, Clayton Loosli showed that serum antibody protected mice against influenza viral pneumonia. Flu shots in humans are designed to maximize serum antibody. They greatly reduce mortality but are variable in their ability to protect against illness. In order to understand this variability, our laboratory has long tried to clarify the relative roles of local and systemic antibody in preventing and promoting recovery from both upper and lower respiratory tract infection with the influenza virus. The role of systemic humoral and cell-mediated immunity in preventing influenza was examined in a ferret study done by W. Henry Barber.
Ferrets are susceptible to the flu.
They also have a long trachea, which makes it surgically possible to create an anatomically isolated tracheal pouch. The pouch enabled us to study responses to infection of the nose or trachea separately. The infection did not spread beyond the pouch. Three weeks after recovery from the infection, when the animals exhibited peak serum antibody levels against the virus, they were rechallenged with the identical virus in both the pouch and nose. The pouch was immune from infection, but rhinitis developed in all animals and they shed virus from the nose.