GRANULOCYTE-MACROPHAGE COLONY-STIMULATING FACTOR PROMOTES PROLONGED SURVIVAL AND THE SUPPORT OF VIRULENT INFECTION BY AFRICAN SWINE FEVER VIRUS OF MACROPHAGES GENERATED FROM PORCINE BONE-MARROW AND BLOOD

Long-surviving cultures of non-adherent cells of the monocyte-macropha ge lineage were established from the bone marrow and blood of weanling pigs by culturing cells from these tissues in the presence of recombi nant porcine granulocyte-macrophage colony stimulating factor (GM-CSF) . The cells increased in number, principally during the first 4 weeks of culture, bound monoclonal antibodies recognizing porcine macrophage antigens and avidly phagocytosed latex particles. The GM-CSF generate d mononuclear phagocytes were highly infectable with a virulent Malawi isolate of African swine fever virus (ASFV) and able to generate leve ls of virus progeny similar to those produced by fresh ly isolated pig macrophages. The cultured cells retained their susceptibility to ASFV infection for as long as the cultures survived i.e. for up to 3 month s.