Reliability of a pretransplant i.v. BU test dose performed 2 weeks before myeloablative FluBu conditioning regimen.

A pretransplant test dose of i.v. BU was previously used in pediatric patients undergoing a reduced-intensity allogeneic hematopoietic SCT (HSCT). Here, we used a BU test dose in 23 adult patients who were not pancytopenic and underwent a myeloablative allogeneic HSCT prepared with fludarabine and i.v. BU (FluBU). Pharmacokinetics (PK) of BU were calculated after a test dose (0.8 mg/kg) was performed 2 weeks before transplant. Targeted BU area under the curve (AUC) range was 4800-5200 microM min. The mean BU dose calculated after the test dose was 3.5+/-0.5 mg/kg. To validate the test dose, PK studies were repeated in 17 patients after the first dose of BU during the conditioning regimen. An AUC below the therapeutic value of 4000 microM min was observed in 23% of the patients receiving a wt-based dose and in 0% of patients whose dose was calculated on the basis of the test dose (P=0.03). In patients who had a test dose, a significant correlation (P<0.0001) between the first and subsequent doses of BU during the conditioning regimen was observed. Our findings may allow more centers to pursue transplant strategies with targeted BU by overcoming the time limitation for PK studies during the conditioning regimen.

Cloning of the cellular receptor for feline leukemia virus subgroup C (FeLV-C), a retrovirus that induces red cell aplasia.

Feline leukemia virus-C (FeLV-C) causes red cell aplasia in cats, likely through its interaction with its cell surface receptor. We identified this receptor by the functional screening of a library of complementary DNAs (cDNA) from feline T cells. The library, which was cloned into a retroviral vector, was introduced into FeLV-C-resistant murine (NIH 3T3) cells. The gene conferring susceptibility to FeLV-C was isolated and reintroduced into the same cell type, as well as into FeLV-C-resistant rat (NRK 52E) cells, to verify its role in viral infection. The receptor cDNA is predicted to encode a protein of 560 amino acids with 12 membrane-spanning domains, termed FLVCR. FLVCR has significant amino acid sequence homology with members of the major facilitator superfamily and especially D-glucarate transporters described in bacteria and in C. elegans. As FeLV-C impairs the in vivo differentiation of burst-forming unit-erythroid to colony-forming unit-erythroid, we hypothesize that this transporter system could have an essential role in early erythropoiesis. In further studies, a 6-kb fragment of the human FLVCR gene was amplified by polymerase chain reaction from genomic DNA, using homologous cDNA sequences identified in the human Expressed Sequence Tags database. By radiation hybrid mapping, the human gene was localized to a 0.5-centiMorgan region on the long arm of chromosome 1 at q31.3.