Cathepsin G and neutrophil elastase play critical and non-redundant roles in lung protective immunity against S. pneumoniae in mice

Neutrophil serine proteases cathepsin G (CtsG), neutrophil elastase (NE) and proteinase-3 (PR3) have recently been shown to contribute to killing of Streptococcus pneumoniae in vitro. However, their relevance in lung protective immunity against different serotypes of S. pneumoniae in vivo has not been determined so far. We here infected CtsG-deficient mice and CtsG/NE deficient mice with two serotypes of S. pneumoniae exhibiting different virulence profiles. Despite similar neutrophil recruitment, both CtsG KO mice and, even more accentuated, CtsG/NE KO mice infected with serotype 19 S. pneumoniae demonstrated a…