It has also been postulated that frequent, high doses of virus given before an antibody response peaks or cytotoxic chemotherapy-mediated attenuation of the antibody titer might enhance systemic delivery of virus to tumor tissue.4 More recently, preclinical data have suggested that the antireovirus neutralizing antibody response may, paradoxically, enhance therapy in mouse models.5 6 This effect, which occurs after cotreatment with granulocyte-macrophage colony-stimulating factor, was predicated on enhanced monocyte/macrophage virus carriage and delivery to tumor. The gene discussed is CSF2; the disease is neoplasm.