(Montana State University - Bozeman, College of Agriculture, 2006) McNamee, Lynnelle Ann; Chairperson, Graduate Committee: Allen G. Harmsen.
Influenza infections result in increased susceptibility to a secondary Streptococcus pneumoniae infection. The aim of the present studies was to determine the mechanism(s) responsible for this increase in susceptibility. Using an in vivo co-infection model, we found that susceptibility to S. pneumoniae was significantly increased at 6 days but not 3 days after an influenza infection. We depleted mice of neutrophils and found that neutrophils were important in the response to S. pneumoniae in mice infected with bacteria only or those infected with influenza for 3 days prior to a S. pneumoniae infection. However, at 6 days, neutrophil depletion did not alter the response to bacterial growth, indicating that neutrophil function was altered. We measured reactive oxygen species (ROS) generation and phagocytosis of S. pneumoniae by lung and bone marrow neutrophils isolated from mice infected with influenza for 3 or 6 days and compared these to neutrophils from either mice stimulated with LPS to induce neutrophil migration or from uninfected mice.
