Parvovirus B19-induced perturbation of human megakaryocytopoiesis in vitro

Abstract

Parvovirus B19 infection leads to transient aplastic crises in individuals with chronic hemolytic anemias or immunodeficiency states. An additional unexplained sequela of B19 infection is thrombocytopenia. Because B19 is known to have a remarkable tropism for human erythropoietic elements, and is not known to replicate in nonerythroid cells, the etiology of this thrombocytopenia is uncertain. We sought to define the pathobiology of B19-associated thrombocytopenia by examining the role of B19 on in vitro megakaryocytopoiesis. B19 infection of normal human bone marrow cells significantly suppressed megakaryocyte (MK) colony formation compared with mock-infected cells. No such inhibition was observed with a nonpathogenic human parvovirus, the adeno-associated virus 2 (AAV). The B19-MK cell interaction was also studied at the molecular level. Whereas low-density bone marrow cells containing erythroid precursor cells supported B19 DNA replication, no viral DNA replication was observed in B19-infected MK-enriched fractions as determined by the presence of viral DNA replicative intermediates on Southern blots. However, analysis of total cytoplasmic RNA isolated from B19-infected MK fractions showed a low-level expression of the B19 genome as detected by quantitative RNA dot blots as well as by Northern analysis. Furthermore, a frame-shift mutation in a recombinant AAV-B19 hybrid genome segment that encodes the viral nonstructural (NS1) protein significantly reduced the observed inhibition of MK colony formation. These studies indicate tissue- tropism of B19 beyond the erythroid progenitor cell, and lend support to the hypothesis that B19 genome expression may be toxic to cell populations that are nonpermissive for viral DNA replication.

Thrombocytopenia in hydropic fetuses with parvovirus B19 infection: incidence, treatment and correlation with fetal B19 viral load

“…The NS1 gene of B19V may be responsible for this direct cytotoxicity to megakaryocytes. 12 An inhibitory effect of this NS1 protein on the colony-forming ability of megakaryocytic progenitor cells in vivo was confirmed in an animal model of parvovirus infection. The degree of inhibitory effect was dependent on the parvovirus infective load, and the depletion of megakaryocyte progenitor cells in the bone marrow appeared to coincide with erythroid progenitor depletion.…”

Parvovirus B19 infection in Taiwanese patients with hematological disorders

“…of B19 beyond the erythroid progenitor cell [Murray et al, 1994]. Previous studies also demonstrated that NS-1 protein, produced by parvovirus B19, could inhibit megakaryocyte colony formation [Ozawa et al, 1988;Srivastava et al, 1990]. Whether B19 infection is implicated in the pathogenesis of ITP in adult patients remains controversial [Lefrere et al, 1989;Van Elsacker-Niele et al, 1996].…”

Human parvovirus B19‐induced acquired pure amegakaryocytic thrombocytopenia

“…Parvoviruses have a remarkable tissue tropism for erythroid elements in the bone marrow and are known to cause transient aplastic crisis in patients with various haemolytic anaemias (Young & Brown, 2004) but their relationship to platelets is not well documented. In vitro exposure of human bone marrow cells to parvovirus has been shown to significantly suppress megakaryocyte colony formation (Srivastava et al, 1990). This may be the mechanism of amegakaryocytic thrombocytopenic purpura secondary to parvovirus.…”