In vitro myelosuppressive effects of the parvovirus minute virus of mice (MVMi) on hematopoietic stem and committed progenitor cells

The interaction of two strains of the parvovirus minute virus of mice (MVM) with the mouse hematopoietic system has been studied. The immunosuppressive strain MVMi, but not the prototype virus MVMp, inhibited hematopoiesis in vitro, as judged by colony-forming assays of the erythroid burst-forming unit and granulocyte-monocyte colony- forming unit (CFU-GM) progenitors. Interestingly, primitive hematopoietic cells of the stem compartment (CFU-S12d), were equally susceptible to the MVMi cytotoxic infection, unravelling an unprecedented feature of virus-hematopoiesis interactions. The replication of both strains of MVM virus was evaluated in primary myeloid cells of long-term bone marrow cultures. A high viral DNA synthesis and maturation was observed in MVMi-infected myeloid cells, but it was undetectable in MVMp infections; moreover, the expression of the cytotoxic nonstructural NS-1 protein, a more reliable parameter of cell permissiveness to MVM infection, was only detected in MVMi- infected cells. Correspondingly, MVMi was propagated to high titers of infectious virus and it mediated an acute myelosuppression in these cultures. We conclude that MVMi has a wider tropism than was previously suspected and it is proposed that cytotoxic infection of hematopoietic stem cells, besides that of committed progenitors, may provide an additional basis to understand the pathogenesis of certain animal and human bone marrow failures of viral etiology.