Pigs, PAMs and Pathogens: using primary alveolar macrophages from abattoir acquired porcine lungs to model pulmonary infections

The similarity between the porcine and human immune system makes pigs an ideal model for studying infectious disease. We have been using alveolar macrophages recovered from abattoir-sourced porcine lungs to create a model to study Streptococcus pneumoniae infections in the lung. Pneumonia is a leading cause of death from infectious disease, with S. pneumoniae the most common cause of bacterial pneumonia. Although much studied, there is still a lot we don’t know about the early stages of infection. Recent research in our lab has found a previously unknown intracellular phase for S. pneumoniae within splenic macrophages Alveolar macrophages were recovered by bronco-alveolar lavage and used in gentamicin protection assays. Macrophages challenged with S. pneumoniae at an MOI of 25 bacteria per cell were found to contain live bacteria up to 5 h after infection. Analysis of samples collected at 45, 90, 180 and 300 min after challenge found less than 10 % of the challenge dose present at 45 min, decreasing to 0.02 % after 5 h. The presence of bacteria inside the macrophages was confirmed by confocal microscopy. Studies are on-going to unpick the processes that allow the bacteria to resist phagocytosis by the macrophages, and to use the model to investigate the interaction of the macrophages with other respiratory pathogens. The use of abattoir-acquired porcine cells contributes to the 3Rs – reducing and replacing laboratory animals, and refinement of method as pigs are more akin to humans than mice. J. McNicholl is sponsored by the Daphne Jackson Trust.