A model of Staphylococcus aureus-induced pneumonia in adult, immunocompetent C57BL/6J mice is described. This model closely mimics the clinical and pathological features of pneumonia in human patients. Using this system, we defined a role for S. aureus strain Newman surface proteins and secreted exotoxins in pneumonia-related mortality.Staphylococcus aureus is an important bacterial pathogen causing pneumonia in both adult and pediatric populations. In recent reports, workers have described the growing incidence of severe S. aureus pneumonia in otherwise healthy individuals, often caused by multi-drug-resistant strains (8, 9). In addition, S. aureus remains one of the most common causes of ventilator-associated pneumonia, contributing to significant morbidity and mortality (18). At present, little is known about the S. aureus virulence factors that play a role in lower respiratory tract disease. The development of an adult, immunocompetent animal model system recapitulating S. aureus pneumonia would provide a useful tool for investigating such factors.To date, small-animal models of S. aureus pneumonia have relied on the use of surgical inoculation methods or infection of immunocompromised animals (6, 17). While these models highlight the inflammatory response to intrapulmonary S. aureus, detailed characterization of S. aureus-encoded virulence factors has not been possible as the organisms are rapidly cleared from the lungs. A murine model of pulmonary infection with agar-embedded S. aureus defined a role for coagulase in hematogenous infection (34), while a neonatal mouse model of S. aureus pneumonia revealed the importance of the accessory gene regulator A (agrA), sarA, and staphylococcal protein A (spa) in the development of disease (10, 13). Together, the data suggest that multiple S. aureus virulence factors contribute to the pathogenesis of pneumonia.We sought to develop a transnasal murine model of S. aureus pneumonia in adult, immunocompetent animals to permit investigation of virulence factors. To define infection parameters leading to evidence of pneumonia in 7-week-old C57BL/6J mice (Jackson Laboratories), groups of 20 animals were inoculated via the intranasal route with either phosphate-buffered saline (PBS) or one of three doses of S. aureus Newman, a human clinical isolate (7). Following 1:100 dilution of an overnight culture into fresh tryptic soy broth, staphylococci were grown with shaking at 37°C to an optical density at 660 nm of 0.5. Culture aliquots (50 ml) were sedimented by centrifugation, and staphylococci were washed and suspended in 750 l PBS. Animals were anesthetized with ketamine and xylazine as previously described (21). After appropriate anesthesia was documented, 30 l of bacterial slurry was inoculated into the left nare, and animals were held upright for 1 min postinoculation. All animals were given food and water ad libitum and observed continually for 72 h. Immediately following inoculation, all animals displayed labored breathing marked by a high respiratory rate and exagger...

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Background Interleukin-4 (IL-4) and STAT6 play an important role in progression of allergic airway disease (AAD) or asthma. IL-4 and STAT6 mediate T helper 2 (Th2) responses in T cells, and immunoglobulin class switching to IgE in B cells. Both, Th2 responses and IgE promote the asthmatic condition. We have previously demonstrated that PARP-14, a member of the poly ADP-ribose polymerase (PARP) family of proteins regulates the transcription function of STAT6. However, the role of PARP-14 in AAD is not known. Objective Here we investigate the role of PARP-14 and the enzyme activity associated with it in AAD dependent on airway hyper-responsiveness (AHR) and lung inflammation. We also elucidate the mechanism by which PARP-14 regulates AAD. Methods The role of PARP-14 and its enzyme activity in AAD and Th2 differentiation were examined using a mouse model of AAD and in vitro T helper cell differentiation. Results PARP-14 deficient animals when compared to controls show reduced lung pathology and IgE. Treating mice with a pharmacological inhibitor for PARP activity reduced the severity of AHR and lung inflammation. Mechanistically, our data indicate that PARP-14 and its enzyme activity aid in the differentiation of T cells towards a Th2 phenotype by regulating the binding of STAT6 to the Gata3 promoter. Conclusion PARP-14 and the catalytic activity associated with it promote Th2 differentiation and AAD in a murine model, and targeting PARP-14 may be a potential new therapy for allergic asthma.