Myeloproliferative sarcoma virus (MPSV), a new tool for the study of hematopoiesis.

MPSV induces a myeloproliferative syndrome in susceptible mice associated with an invasion of hematopoietic and nonhematopoietic organs with tumor nodules. The effect of the virus on the various hematopoietic precursors (CFU-S, CFU-C, CFU-E, BFU-E) was studied in vivo in the spleen, blood, and bone marrow, and in vitro, using colony assays in semisolid medium. After in vivo and in vitro infection MPSV induces the appearance of CFU-C, independent of added colony-stimulating activity and of pure and mixed BFU-E, independent of burst-promoting activity. MPSV also induces in vivo an amplification of the size and concentration of the hematopoietic system, including hematopoietic stem cells. MPSV infection may also alter the hemapoietic microenvironment. Modification of the disease by total body irradiation followed by bone marrow stem cell reconstitution or by splenectomy is compatible with mediation of the virus effect at the level of hematopoietic microenvironment. MPSV may constitute a new tool to study the regulation of murine hematopoiesis and viral genetic information, which can specifically induce characteristic disturbances of this system.