Exercise, alveolar macrophage function, and susceptibility to respiratory infection

Davis, J. M., M. L. Kohut, L. H. Colbert, D. A. Jackson, A. Ghaffar, and E. P. Mayer. Exercise, alveolarmacrophage function, and susceptibility to respiratory infection.J. Appl. Physiol. 83(5):1461-1466, 1997.The effects of exercise on susceptibility torespiratory infection were determined by using a murine model ofintranasal challenge with herpes simplex type 1 virus (HSV-1). Twodoses of treadmill exercise were assessed: moderate short-term (30 min)exercise and prolonged strenuous exercise to voluntary fatigue(2.5-3.5 h). Morbidity and mortality among exercised and controlmice were compared after intranasal challenge with HSV-1. We alsoassessed the ability of alveolar macrophages to restrict HSV-1 viralreplication (intrinsic resistance) among exercise and control groups ofmice at several time points postexercise. Exercise to fatigue followedby exposure to viral infection resulted in greater morbidity andmortality than either no exercise or short-term moderate exercise. Inaddition, antiviral resistance of macrophages obtained from the lungsof both exercised groups was suppressed, albeit for a longer durationin the fatigued group. These data are particularly important in thatthey identify an exercise-induced decrease in antiviral resistance of aspecific component of the immune system within the lungs, inconjunction with increased susceptibility to respiratory infection invivo. The specific mechanism of decreased antiviral resistance ofalveolar macrophages and its role in respiratory infection afterexercise remains to be determined.