ALBERT

Description: Cytopenia after high-dose chemotherapy and autologous stem cell reinfusion is a major cause of morbidity. Ex vivo cultured expansion and differentiation of CD34+ peripheral blood progenitor cells (PBPC) to neutrophil precursors may shorten the neutropenic period further. We explored the use of these ex vivo cultured PBPCs in nine patients with metastatic breast cancer. All underwent PBPC mobilization with cyclophosphamide, VP-16, and G-CSF. Subsequently, they underwent four to five apheresis procedures. One apheresis product from each patient was prepared using the Isolex 300 Magnetic Cell Separation System (Baxter Immunotherapy, Irvine, CA) to obtain CD34+ cells. These cells were then cultured in gas permeable bags containing serum-free X-VIVO 10 (BioWhittaker, Walkersville, MD) medium supplemented with 1% human serum albumin and 100 ng/mL PIXY321. At day 12 of culture the mean fold expansion was 26x with a range of 6 to 64x. One patient's cells did not expand because of a technical difficulty. The final cell product contained an average of 29.3% CD15+ neutrophil precursors with a range of 18.5% to 48.1%. The patients underwent high-dose chemotherapy with cyclophosphamide, carboplatin, and thiotepa. On day 0, the cryopreserved PBPCs were reinfused and on day +1 the 12-day cultured cells were washed, resuspended, and reinfused into eight of nine patients. One patient was not infused with cultured cells. The mean number of cultured cells reinfused was 44.6 x 10(6) cells/kg with a range of 0.8 to 156.6 x 10(6) cells/kg. No toxicity was observed after reinfusion. The eight patients have recovered absolute neutrophil counts 〉 500/microL on a median of 8 days (range 8 to 10 days); the median platelet transfusion independence occurred on day 10 (range 8 to 12 days) and platelet counts 〉 50,000/microL were achieved by day 12 (range 9 to 14) for the seven patients whose platelet counts could be determined. Expanded CD34+ selected PBPC can be obtained and safely reinfused into patients.

Description: Cytopenia after high-dose chemotherapy and autologous stem cell reinfusion is a major cause of morbidity. Ex vivo cultured expansion and differentiation of CD34+ peripheral blood progenitor cells (PBPC) to neutrophil precursors may shorten the neutropenic period further. We explored the use of these ex vivo cultured PBPCs in nine patients with metastatic breast cancer. All underwent PBPC mobilization with cyclophosphamide, VP-16, and G-CSF. Subsequently, they underwent four to five apheresis procedures. One apheresis product from each patient was prepared using the Isolex 300 Magnetic Cell Separation System (Baxter Immunotherapy, Irvine, CA) to obtain CD34+ cells. These cells were then cultured in gas permeable bags containing serum-free X-VIVO 10 (BioWhittaker, Walkersville, MD) medium supplemented with 1% human serum albumin and 100 ng/mL PIXY321. At day 12 of culture the mean fold expansion was 26x with a range of 6 to 64x. One patient's cells did not expand because of a technical difficulty. The final cell product contained an average of 29.3% CD15+ neutrophil precursors with a range of 18.5% to 48.1%. The patients underwent high-dose chemotherapy with cyclophosphamide, carboplatin, and thiotepa. On day 0, the cryopreserved PBPCs were reinfused and on day +1 the 12-day cultured cells were washed, resuspended, and reinfused into eight of nine patients. One patient was not infused with cultured cells. The mean number of cultured cells reinfused was 44.6 x 10(6) cells/kg with a range of 0.8 to 156.6 x 10(6) cells/kg. No toxicity was observed after reinfusion. The eight patients have recovered absolute neutrophil counts 〉 500/microL on a median of 8 days (range 8 to 10 days); the median platelet transfusion independence occurred on day 10 (range 8 to 12 days) and platelet counts 〉 50,000/microL were achieved by day 12 (range 9 to 14) for the seven patients whose platelet counts could be determined. Expanded CD34+ selected PBPC can be obtained and safely reinfused into patients.

Description: Botrocetin, a component of Bothrops jararaca venom, induces von Willebrand factor (vWF)-dependent platelet agglutination and has been proposed as an alternative agent to ristocetin for evaluating vWF function. However, important differences between the vWF-platelet interactions induced by these two agents have suggested that different regions of vWF and the platelet may be involved in the interactions induced by the two agonists. We have recently demonstrated that binding of vWF to the platelet glycoprotein (GP) Ib receptor, either induced by ristocetin or as occurs spontaneously with asialo-vWF or vWF from IIb von Willebrand disease, is mediated by a domain residing on a 52/48- kilodalton (kD) tryptic fragment of vWF. This fragment extends from amino acid residue Val (449) to Lys (728). We have now found that this 52/48-kD fragment blocks botrocetin-induced binding of vWF to platelets and completely inhibits botrocetin-induced platelet agglutination. These results provide evidence that the vWF domain-mediating, botrocetin-induced platelet agglutination lies within the region delimited by this fragment and is therefore close to or identical with that which mediates ristocetin-induced binding and spontaneous binding of vWF to platelet GPIb. Anti-GPIb monoclonal antibodies also blocked agglutination, which showed that botrocetin, like ristocetin, induces binding of vWF to the GPIb receptor.

Description: In order to evaluate the role of proteolysis in acquired von Willebrand's disease (vWD) associated with the myeloproliferative syndrome, we have determined the relative quantity of von Willebrand factor (vWF) fragments as compared with the intact 225 kDa subunit in four patients. The plasma vWF of each individual lacked large multimers; each had a prolonged bleeding time; and both platelet and leukocyte counts were elevated. Plasma was obtained from blood drawn into 1 mmol/L leupeptin, 6 mmol/L N-ethylmaleimide, and 5 mmol/L EDTA to prevent in vitro proteolysis. vWF was isolated from plasma by immunoadsorbent chromatography, reduced, subjected to SDS-5% polyacrylamide gel electrophoresis, and immunoblotted with a mixture of 55 anti-vWF monoclonal antibodies. In three patients with essential thrombocytosis (ET) the 176 and 140 kDa fragments were increased in proportion to the intact 225 kDa subunit indicating increased proteolysis. Treatment of one ET patient with CCNU (Lomustine) decreased the platelet count and, to a lesser extent, the white blood cell count. This was associated with a correction of the bleeding time, a partial correction of the multimeric abnormality, and a lessening of vWF cleavage. In a patient with polycythemia rubra vera (PRV) the proportion of the 176 kDa fragment was increased to the upper limit of normal but there was no definite evidence of increased proteolysis. These studies provide evidence that proteolysis plays a role in the acquired von Willebrand's disease associated with the myeloproliferative syndrome. However, other mechanisms must also be considered.

Description: Type IIB von Willebrand disease is characterized by enhanced ristocetin- induced platelet aggregation and absence of large von Willebrand factor multimers from plasma. An alteration of the von Willebrand factor molecule resulting in increased reactivity with platelets appears to be the basis for these abnormalities. We have now identified a new variant of type IIB von Willebrand disease in a family in which the four affected members also have chronic thrombocytopenia, in vivo platelet aggregate formation, and spontaneous platelet aggregation in vitro. In spite of repeatedly prolonged bleeding times and persistent thrombocytopenia, their bleeding diathesis is only moderate.

Description: In Type I von Willebrand disease, the whole series of von Willebrand factor (vWF) multimers is present in plasma, but all are decreased in quantity. No structural abnormality of individual multimers has been demonstrated so far in these patients. We now describe five individuals, from two unrelated families, who had this form of the disease and in whom the complex banding pattern of each vWF multimer was markedly abnormal. Inheritance was autosomal dominant and the clinical expression was mild. A bleeding history was elicited in three of the patients and included recurrent epistaxis, menometrorrhagia, and bleeding following tooth extraction. Replacement therapy had never been required. Although vWF levels in plasma were within the normal range in all of them, the ristocetin cofactor activity was decreased in four, and the bleeding time was prolonged in three. Analysis of vWF multimeric structure by agarose gel electrophoresis, including a newly developed high-resolution technique, demonstrated that the main band of each multimer was present, but a second, well-defined band always seen in normal individuals was missing in the patients. Two additional bands had altered mobility and were less well defined than in normal subjects, and a fifth, less intense band was also undetectable in the patients. Treatment with 1-deamino-8-D-arginine vasopressin (DDAVP) was assessed in two patients. It caused the circulating levels of vWF to increase and correct the bleeding time, but did not alter the structural abnormality. This study describes, therefore, a new variant form of Type I von Willebrand disease with aberrant structure of individual repeating multimers and an associated functional abnormality of vWF. In keeping with previously accepted terminology, the designation of Type IC von Willebrand disease has been adopted for this new variant.

Description: Congenital deficiency of factor XI is a rare condition associated with a mild to moderate bleeding diathesis that is most commonly found in persons of Jewish ancestry. The disorder has been reported sporadically in a number of other ethnic groups, but rarely in the black population. We report on the genetic analysis of the factor XI genes of two African American patients: a 9-year-old boy (the propositus) with mild factor XI deficiency and his mother. Both individuals have lifelong histories of excessive bleeding. Dideoxyfingerprinting, a technique combining components of single-strand conformational polymorphism analysis and dideoxy-chain termination sequencing, was used in the analysis. Both patients were found to be heterozygous for a mutation changing serine 248 to glutamine, whereas the propositus was heterozygous for an additional mutation on the paternal allele changing glutamine 226 to arginine. Both mutations reside in the third apple domain of the factor XI heavy chain, an area that has been shown to contain binding sites for factor IX, platelets, and glycosaminoglycans. Previously reported mutations in the factor XI gene seem to cause deficiency primarily by reducing protein expression. Because both alleles in the propositus contain amino acid substitutions, the significant amount of circulating factor XI in his plasma must be comprised entirely of abnormal molecules. Factor XI circulates as a homodimer, and the presence of mutations in both alleles of the factor XI gene suggests that his bleeding disorder is caused in part by the effect of the two abnormal gene products forming dimers in different combinations. Three neutral (not associated with amino acid changes) DNA polymorphisms were also identified in the two subjects: a C to T change at nucleotide 472 in exon 5, A to G at nucleotide 844 in exon 8, and T to C at nucleotide 1234 in exon 11. Analysis of a random sample of normal volunteers showed that these polymorphisms are relatively common, with allele frequencies of 7.4%, 19%, and 18%, respectively. This suggests that there is considerable genetic heterogeneity in the factor XI gene. © 1998 by The American Society of Hematology.

Description: Children with sickle cell disease (SCD) and stroke receive chronic transfusions to prevent stroke recurrence. Transfusion risks including infection, erythrocyte allosensitization, and iron overload suggest a need for alternative therapies. We previously used hydroxyurea (HU) and phlebotomy in two young adults with SCD and stroke as an alternative to transfusions. We have now prospectively discontinued transfusions in 16 pediatric patients with SCD and stroke. Reasons to discontinue transfusions included erythrocyte alloantibodies or autoantibodies, recurrent stroke on transfusions, iron overload, noncompliance, and deferoxamine allergy. HU was started at 15 mg/kg/d and escalated to 30 mg/kg/d based on hematologic toxicity. Patients with iron overload underwent phlebotomy. The children have been off transfusions 22 months, (range, 3 to 52 months). Their average HU dose is 24.9 ± 4.2 mg/kg/d, hemoglobin concentration is 9.4 ± 1.3 g/dL, and mean corpuscular volume (MCV) is 112 ± 9 fL. Maximum percentage fetal hemoglobin (%HbF) is 20.6% ± 8.0% and percentage HbF-containing erythrocytes (%F cells) is 79.3% ± 14.7%. Fourteen patients underwent phlebotomy with an average of 8,993 mL (267 mL/kg) removed. Serum ferritin has decreased from 2,630 to 424 ng/mL, and 4 children have normal ferritin values. Three patients (19%) had neurological events considered recurrent stroke, each 3 to 4 months after discontinuing transfusions, but before maximal HU effects. These preliminary data suggest some children with SCD and stroke may discontinue chronic transfusions and use HU therapy to prevent stroke recurrence. Phlebotomy is well-tolerated and significantly reduces iron overload. Modifications in HU therapy to raise HbF more rapidly might increase protection against stroke recurrence.

Description: We used immunoblotting of purified factor VIII coagulant protein (FVIII) to localize FVIII inhibitor epitopes in 76 inhibitor plasmas to either the 92-kd FVIII polypeptide (and its 54-kd and/or 44-kd thrombin fragments), the 80-kd polypeptide (and its 72-kd thrombin fragment), or both of these polypeptides. We also used immunoblotting to examine the immunoglobulin class and subclass content of 12 inhibitors with monoclonal antibodies specific for human IgG subclasses and IgM. Seven hemophilic (alloantibody) and five spontaneous (autoantibody) inhibitors contained IgG-1 and IgG-4 antibody; one of the spontaneous inhibitors also contained IgG-3. In one hemophilic inhibitor, the IgG-4 component reacted strongly with the 92-kd and 80-kd polypeptides, whereas the IgG-1 component reacted only minimally with the 92-kd polypeptide although its reactivity with the 80-kd polypeptide was strong. Another hemophilic inhibitor was affinity purified and subjected to quantitative radial immunodiffusion, and the presence of IgG-1 and IgG-4 antibody was confirmed. We conclude that the inhibitors examined are not monoclonal but are probably of restricted polyclonal origin and that different IgG subclasses in an inhibitor plasma can have different degrees of FVIII polypeptide reactivity.

Description: Sialophorin, previously called gpL115, is the heavily sialylated surface protein that is defective in lymphocytes of Wiskott-Aldrich syndrome patients. Using the monoclonal antibody L10 as a probe, sialophorin expression was detected on isolated T lymphocytes and thymocytes, B cell lines, monocytes, neutrophils, and platelets, but not on erythrocytes, fibroblasts, and glioblastoma cells. This unusual distribution pattern suggests that sialophorin is expressed on all circulating cells except erythrocytes. Trace amounts of the sialophorin molecules on lymphocytes are incompletely sialylated, but significant amounts of the molecules on thymocytes are incompletely sialylated. The molecular form of sialophorin on T lymphocytes, thymocytes, and monocytes is the previously characterized species of apparent mol wt 115,000. A newly described sialophorin species of apparent mol wt 135,000 was found on neutrophils and platelets. The 115,000 lymphocyte/monocyte form and the 135,000 platelet/neutrophil form were shown to be substantially similar. The two forms have approximately the same content of sialylated O-linked carbohydrate units since both undergo the same atypical shift in electrophoretic mobility on desialylation. Both contain the epitope recognized by the monoclonal antibody L2 and the epitope recognized by L10 antibody. Moreover, evidence from another study indicates that the polypeptide portions are identical, cumulatively suggesting that 115,000 sialophorin and 135,000 sialophorin are identical except for the presence on the latter of additional neutral saccharide residues.