Recombinant parvovirus B19 empty capsids inhibit fetal hematopoietic colony formation in vitro

Erythroid lineage cells are target cells for human parvovirus B19, and a na tural infection often results in transient anemia. To determine whether rec ombinant B19 capsid proteins (VP1/VP2) also inhibit human hematopoietic pro genitor growth, a model system was set up, The B19 capsids were inoculated into primary cultures of hematopoietic stem cells derived from human fetal liver, resulting in a 70-95% reduction of BFU-E (burst-forming unit erythro id cells) as compared with the medium control. A similar effect was seen in human hematopoietic stem cell cultures derived from cord blood and adult b one marrow. Preincubation of the B19 capsids with either a monoclonal antib ody to the virus or with B19 IgG positive human sera reduced the inhibitory effect, Furthermore, the inhibitory effect could be reduced by preincubati ng the target cells with a monoclonal antibody to the cellular receptor for the virus, the P antigen. These findings thus show that the inhibition of colony formation of human hematopoietic stem cells can occur in the absence of parvovirus B19 nonstructural proteins. We speculate that B19 capsid cou ld provide a possible strategy to downregulate indigenous hematopoiesis in fetal stem cell transplantations. Copyright (C) 2001 S. Karger AG, Basel.