Japanese journal of infectious diseases
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Jpn. J. Infect. Dis. · Jan 2011
Increase of apoptosis in a murine model for severe pneumococcal pneumonia during influenza A virus infection.
The mechanisms of severe pneumonia caused by co-infection of bacteria and influenza A virus (IAV) have not been fully elucidated. We examined apoptosis and inflammatory responses in a murine model for pneumococcal pneumonia during IAV infection. Inflammation, respiratory epithelium apoptosis, and inflammatory-cell infiltration increased in a time dependent manner in the lungs of mice co-infected with Streptococcus pneumoniae and IAV, in comparison with those infected with either S. pneumoniae or IAV. ⋯ In contrast, in mice infected with either IAV or S. pneumoniae, apoptosis and activation of factors related to caspase-3 peaked at 48 h. Furthermore, Fas-associated death domain was significantly expressed in the lungs of co-infected mice 24 h after S. pneumoniae infection. These data suggest that early onset of apoptosis and its related factors play important roles in fulminant pneumonia resulting from bacterial pneumonia complicated by co-infection with influenza virus.