INTERACTION OF BOVINE RESPIRATORY SYNCYTIAL VIRUS WITH BOVINE ALVEOLAR MACROPHAGES IN-VIVO - EFFECTS OF VIRUS-INFECTION UPON SELECTED CELL FUNCTIONS

The effect of bovine respiratory syncytial virus (BRSV) upon alveolar macrophage (AM) function was investigated using an in vivo calf inocul ation model. Alveolar macrophages were collected sequentially from liv e calves at multiple time points during the 14 day period following vi ral inoculation. Alveolar macrophages from bronchoalveolar lavage flui ds were purified by density gradient centrifugation (> 95% AM) prior t o in vitro evaluation of cell functions. There were significant but va riable and inconsistent differences in the functions of AM from the BR SV inoculated calves compared to the control calves. Fc-receptor media ted phagocytosis was either increased or unchanged by BRSV inoculation . Nonopsonized phagocytosis was decreased during the early postinocula tion period and later increased. There was a variable effect on AM pha gosome lysosome fusion with increased fusion activity on postinoculati on days 2 through 5, 7 and 12 but reduced activity on days 6 and 10. T he AM respiratory burst, as measured by nitroblue tetrazolium dye redu ction, was essentially unaffected with a reduction in activity on day 10 only. In this model, BRSV inoculation of calves primarily resulted in an alteration of the membrane associated phagocytic functions of th e alveolar macrophages (p < 0.05).