Persistent B19 Parvovirus Infection in Patients Infected with Human Immunodeficiency Virus Type 1 (HIV-1): A Treatable Cause of Anemia in AIDSOBJECTIVE: To determine the role of B19 parvovirus in red cell aplasia of patients infected with human immunodeficiency virus type 1 (HIV-1). DESIGN: Uncontrolled clinical trial, with assay of serum, peripheral blood cells, and bone marrow for virus using DNA hybridization and immunocytochemistry techniques; these assays were then correlated with clinical findings, results of immunoassays for antivirus antibodies, and with immunoglobulin (Ig) therapy. SETTING: Government medical referral center, and university and private hospitals. PATIENTS: Seven patients with pure red cell aplasia and serologic evidence of infection with HIV-1. MEASUREMENTS AND MAIN RESULTS: All patients had giant pronormoblasts in the bone marrow (present in transient aplastic crisis caused by acute B19 parvovirus infection). High concentrations of B19 parvovirus were demonstrated in sera, in several cases in samples separated by weeks or months. Viral DNA and capsid protein were present in the bone marrow of three patients studied, and active viral replication was detected by southern analysis. There was no antivirus IgG in capture immunoassay and no or very low levels of antivirus IgM. The patients did not have symptoms of fifth disease, the illness caused by this virus in immunologically normal persons. Six patients were treated with a regimen of intravenous commercial immunoglobulin. In all cases, this therapy resulted in rapid reduction in serum virus concentrations and full recovery of erythropoiesis. Relapses in two cases were predicted by DNA hybridization studies, and these cases were successfully retreated. CONCLUSIONS: The B19 parvovirus is a remediable cause of severe chronic anemia in HIV-infected patients. Recognition of and therapy for parvovirus in this population will avoid erythrocyte transfusion and should prevent transmission of the virus to other persons, including immunosuppressed persons and women of child-bearing age.
Identification of a Human Heme Exporter that Is Essential for ErythropoiesisA Heme Export Protein Is Required for Red Blood Cell Differentiation and Iron HomeostasisHemoproteins are critical for the function and integrity of aerobic cells. However, free heme is toxic. Therefore, cells must balance heme synthesis with its use. We previously demonstrated that the feline leukemia virus, subgroup C, receptor (FLVCR) exports cytoplasmic heme. Here, we show that FLVCR-null mice lack definitive erythropoiesis, have craniofacial and limb deformities resembling those of patients with Diamond-Blackfan anemia, and die in midgestation. Mice with FLVCR that is deleted neonatally develop a severe macrocytic anemia with proerythroblast maturation arrest, which suggests that erythroid precursors export excess heme to ensure survival. We further demonstrate that FLVCR mediates heme export from macrophages that ingest senescent red cells and regulates hepatic iron. Thus, the trafficking of heme, and not just elemental iron, facilitates erythropoiesis and systemic iron balance.
Germline ETV6 mutations in familial thrombocytopenia and hematologic malignancyKinetics of Central Nervous System Microglial and Macrophage Engraftment: Analysis Using a Transgenic Bone Marrow Transplantation ModelTo determine the kinetics of tissue macrophage and microglial engraftment after bone marrow (BM) transplantation, we have developed a model using the ROSA 26 mouse. Transplanted ROSA 26 cells can be precisely identified in recipient animals because they constitutively express beta-galactosidase (beta-gal) and neomycin resistance. B6/129 F2 mice were irradiated and transplanted with BM from ROSA 26 donors and their tissues (spleen, marrow, brain, liver, and lung) examined at various time points to determine the kinetics of engraftment. Frozen sections from transplanted animals were stained histochemically for beta-gal to identify donor cells. At 1, 2, 6, and 12 months posttransplantation, 98% to 100% of granulocyte-macrophage colonies were of donor (ROSA 26) origin determined by beta-gal staining and by neomycin resistance. Splenic monocytes/macrophages were 89% donor origin by 1 month confirming quick and complete engraftment of hematopoietic tissues. At this time, only rare ROSA 26 tissue macrophages or microglia were observed. Alveolar macrophage engraftment was evident by 2 months and had increased to 61% of total tissue macrophages at 1 year posttransplantation. The kinetics of liver Kupffer cell engraftment were similar to those seen in the lung. However, donor microglial engraftment remained only 23% of total microglia at 6 months and increased to only 30% by 1 year. Also, donor microglia were predominantly seen at perivascular and leptomeningeal, and not parenchymal, sites. The data show that microglia derive from BM precursors but turn over at a significantly slower rate than other tissue macrophages. No clinical or histological graft-versus-host disease was observed in the recipients of ROSA 26 BM. These kinetics may impact strategies for the gene therapy of lysosomal storage diseases. Because individual donor cells can be identified in situ, the ROSA 26 model should have many applications in transplantation biology including studies of homing and differentiation.