Effect of "in vitro" exposure of bovine alveolar macrophages to different strains of bovine respiratory syncytial virus.

A vaccine strain of respiratory syncytial (RS) virus and an isolate from pneumonic calves (AC2) were inoculated onto cultures of bovine alveolar macrophages recovered by lung lavage, and the functional properties of the cells observed over a period of 10 days. In most cultures no infectious virus was produced although immunofluorescence indicated the presence of virus antigens in some cells. No significant difference was noted between infected and control macrophage cultures in their capacity to phagocytose latex particles (neutral phagocytosis), although the ability to phagocytose complement-coated Candida krusei cells was affected, particularly with the AC2 strain after 6 days. Killing of C. krusei cells was slightly affected by infection of macrophages with the vaccine strain and was dramatically affected by infection with strain AC2. C3b and Fc receptor expression was adversely affected by both virus strains. Production of neutrophil chemotactic factors was increased in cultures infected with both strains, but was greater with AC2, suggesting that some properties of the cells were activated.