Contribution of NOD2 to lung inflammation during Staphylococcus aureus-induced pneumonia.

Staphylococcus aureus is the most commonly found Gram-positive bacterium in patients admitted in intensive-care units, causing septicaemia or pneumonia. In this work, we investigated the role of NOD2 in S. aureus-induced pneumonia. We found that the absence of NOD2 affected weight loss and recovery speed. Nod2-/- mice showed a reduced lung inflammation in comparison to wild-type animals, with lower presence of cytokines in broncho-alveolar lavage fluids and reduced recruitment of neutrophils. Furthermore, histological analysis of the lungs revealed less severe lesions in Nod2-/- mice at day 2 and day 7 post-infection. In conclusion, we demonstrated that NOD2 is not a crucial receptor to fight S. aureus-induced pneumonia, but that it contributes to the inflammatory response in the lungs. Interestingly, the absence of NOD2 led to a lesser inflammation and was finally beneficial for the animal recovery.