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

Erythroid lineage cells are target cells for human parvovirus B19, and a natural infection often results in transient anemia. To determine whether recombinant B19 capsid proteins (VP1/VP2) also inhibit human hematopoietic progenitor 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 erythroid cells) as compared with the medium control. A similar effect was seen in human hematopoietic stem cell cultures derived from cord blood and adult bone marrow. Preincubation of the B19 capsids with either a monoclonal antibody to the virus or with B19 IgG positive human sera reduced the inhibitory effect. Furthermore, the inhibitory effect could be reduced by preincubating 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 could provide a possible strategy to downregulate indigenous hematopoiesis in fetal stem cell transplantations.

Mixed lymphocyte culture of human fetal liver cells.

OBJECTIVE: In order to study the immunological function of the human fetus in the first and second trimesters, mixed lymphocyte culture (MLC) of fetal liver and thymic cells was performed. MLC is a functional test to determine human lymphocyte antigen-D incompatibilities. METHODS: Human fetal liver and thymic tissue was obtained from abortions in gestational weeks 7-17.5. Forty-seven fetuses were studied with one-way MLC. The cells were stimulated by adding irradiated fetal liver cells, adult bone marrow and peripheral blood lymphocytes. The activity was measured as DNA incorporation of radiolabeled thymidine. RESULTS: The results indicate that the human fetus is competent to react as early as 11-12 weeks of gestation and in some cases even earlier. In very immature fetal livers (< 8 weeks), the MLC seems to be inhibited. CONCLUSIONS: Our data suggest that the human fetus can react against foreign transplantation antigens earlier than previous papers have claimed. The onset of reactivity seems to differ considerably among fetuses. The present findings may explain some of the limited success of in utero transplantations of hematopoietic stem cells in human fetuses of normal immunological status.

Prevention of recurrent spontaneous abortion by intravenous immunoglobulin: a double-blind placebo-controlled study.

The aim of this study was to evaluate the therapeutic efficacy of intravenous immunoglobulin (IVIG) in the prevention of recurrent spontaneous abortion (RSA). In a double-blind, randomized, placebo-controlled study, 41 women with a history of unexplained recurrent spontaneous abortion were treated with IVIG or saline infusions during pregnancy. The birth of a child was considered a successful outcome. The overall success rate was 77% in the IVIG group compared with 79% in the placebo group. For women with primary RSA the success rates were 82 (IVIG) and 89% (placebo), and for women with secondary RSA the rates were 73 (IVIG) and 70% (placebo). We found no statistically significant difference in treatment results between IVIG and placebo.