Evaluation of atypical human immunodeficiency virus immunoblot reactivity in blood donors

Blood donors reactive by enzyme-linked immunosorbent assay for antibody to the human immunodeficiency virus (HIV) who showed atypical patterns of viral core protein reactivity on Western blot were monitored for several months. Characterization of their antibodies was performed by 1) use of recombinant HIV proteins; 2) determination of cross-reactivity to HTLV-I, HTLV-II, and HTLV-IV: 3) assessment of immune status; and 4) identification of potentially interfering autoantibodies. Nineteen of 20 donors maintained the same HIV antibody reactivity throughout the follow-up period; the other donor became fully antibody-positive. Eighteen of 20 donors' sera showed clear reactivity with HIV recombinant core proteins. Ten of 19 donor samples demonstrated cross-reactivity to HTLV-IV; 3 of these 10 also cross-reacted with HTLV-I. The immune status of all donors was normal, although the medical histories and HLA antibody screens suggested possible autoimmune reactivity in 9 of 18 donors. During follow-up interviews, three donors reported possible risk factors for HIV infection that had not been acknowledged at the time of blood donation. We conclude that exclusion of donors with these atypical serologic test results is warranted while further studies to determine significance are being conducted.     

Correlation of P-glycoprotein expression and function in childhood acute leukemia: a children's cancer group study

Clinical drug resistance may be attributed to the simultaneous selection and expression of genes modulating the uptake and metabolism of chemotherapeutic agents. P-glycoprotein (P-gp) functions as a membrane-associated drug efflux pump whose increased expression results in resistance to anthracyclines, epipodophyllotoxins, vinca alkaloids, and some alkylating agents. This type of resistance occurs as both de novo and acquired resistance to therapy for leukemia. We have studied P- gp expression and function in childhood acute leukemias by developing a series of doxorubicin- and vincristine-selected CEM, T-cell lymphoblastoid cell lines that recapitulate the low levels of expression and resistance seen clinically. These cell lines have been used to develop flow cytometric assays for the semiquantitative measurements of P-gp expression with the MRK16 monoclonal antibody and P-gp function using the enhanced retention of rhodamine 123 in the presence of verapamil, a resistance modulator. Kolmogorov-Smirnov statistics, represented by the D measurement, are used to determine the difference in level of P-gp expression by comparing MRK16 staining to an IgG2a isotype control. When D is > 0.09, there is an excellent correlation (R = 0.82) between P-gp expression and function. The evaluation of 107 bone marrow specimens from 84 children with lymphoblastic or myelogenous leukemia showed a statistically significant (P = .004) increase in P-gp function at relapse. P-gp expression at relapse, however, approached but did not reach a significant level (P = .097). Using this methodology, we can identify patients with levels of P-gp expression and function that we can define clinically, as well as children with discordant multidrug resistance phenotypes. This study supports the role of P-gp-mediated drug resistance in childhood leukemia and confirms that P-gp expression and function are measurable in their leukemic blasts. These assays provide the means for the in vitro testing of resistance modulators and the monitoring of in vivo response to treatment with these agents.     

Inhibition of endotoxin-induced activation of the coagulation and fibrinolytic pathways using a recombinant endotoxin-binding protein (rBPI23)

A recombinant endotoxin-neutralizing protein, rBPI23, was shown to partially prevent endotoxin-induced activation of the fibrinolytic and coagulation systems in experimental endotoxemia in humans. In a placebo- controlled, blinded crossover study, eight volunteers were challenged twice with an intravenous bolus injection of endotoxin (40 EU/kg of body weight) and concurrently received either rBPI23 (1 mg/kg) or placebo (human serum albumin, 0.2 mg/kg). rBPI23 treatment significantly lowered the endotoxin-induced fibrinolytic response, ie, reduced the release of tissue-type plasminogen activator, urokinase- type plasminogen activator, plasminogen activator inhibitor antigen, and complex formation of plasmin alpha 2-antiplasmin (P = .0078 for each). Plasminogen activator inhibitor activity was also reduced, but not significantly according to the Hochberg method (P = .0304). The endotoxin-induced activation of the procoagulant state as reflected by increase in F1 + 2 fragments and TAT complexes was blunted by rBPI23 infusion (P = .0391 [not significant according to the Hochberg method] and .0078, respectively). These results indicate that rBPI23 is capable of reducing both the activation of the fibrinolytic and the coagulation systems after low-dose endotoxin infusion in humans.     

Effectiveness of methyl-GAG (methylglyoxal-bis[guanylhydrazone]) in patients with advanced malignant lymphoma

We treated 51 patients with advanced malignant lymphoma refractory to conventional therapy with methyl-glyoxal-bis(guanylhydrazone) (methyl- GAG) at doses ranging from 400 to 800 mg/sq m. Therapy was started on a weekly schedule and was switched to every other week in responding patients at the onset of toxicity. Partial responses were observed in 6 of 13 evaluable patients with Hodgkin's disease (46%), 5 of 10 patients with diffuse poorly differentiated lymphocytic lymphoma (50%), 2 of 4 patients with nodular poorly differentiated lymphocytic lymphoma (50%), and 3 of 13 patients with diffuse histiocytic lymphoma (23%). Two of six patients with mycosis fungoides showed objective improvement in cutaneous disease. Toxicity was generally mild and included muscular weakness, myalgia, mucositis, and diarrhea; two patients developed bronchospasm following drug infusions. We conclude that methyl-GAG has major antitumor activity when administered on this schedule to patients with advanced malignant lymphoma. The low degree of toxicity, unique mechanism of action, and minimal myelosuppressive effects suggest that methyl-GAG will prove useful in future trials of combination chemotherapy regimens for the treatment of lymphoma.     

Anemia of the Belgrade rat: evidence for defective membrane transport of iron

The mechanisms underlying the impaired utilization of transferrin-bound iron by erythroid cells in the anemia of the Belgrade laboratory rat were investigated using reticulocytes from homozygous anemic animals and transferrin labeled with 59Fe and 125I. The results were compared with those obtained using reticulocytes from phenylhydrazine-treated rats and iron-deficient rats. Each step in the iron uptake mechanism was investigated, ie, transferrin-receptor interaction, transferrin endocytosis, iron release from transferrin, and transferrin exocytosis. Although there were quantitative differences, no fundamental difference was found in any of the abovementioned aspects of cellular function when the reticulocytes from Belgrade rats were compared with those from iron-deficient animals. The basic defect in the Belgrade reticulocytes must therefore reside in subsequent steps in iron uptake, after it is released from transferrin within endocytotic vesicles, ie, in the mechanism by which it is transferred across the lining membrane of the vesicles into the cell cytosol. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of reticulocyte ghosts extracts demonstrated a prominent protein band of mol wt 69,000 that was absent or present only in low concentration extracts from the other two types of reticulocytes. This may be a result of the genetic defect.     

Factors that affect human hemopoiesis are produced by T-cell growth factor dependent and independent cultured T-cell leukemia-lymphoma cells

Some laboratory results and clinical situations suggest that human T cells may be important in the regulation of growth of hematopoietic cells. Since the discovery of T-cell growth factor (TCGF), systems are now available for the long-term specific in vitro propagation of mature normal or neoplastic human T cells, providing an opportunity to study the influence of T cells on hematopoiesis. Recently, 24 cell lines from patients with cutaneous T-cell lymphoma (CTCL) and T-cell acute lymphoblastic leukemia (T-ALL) were grown with TCGF and then assessed for release of humoral factors that affect hematopoiesis. Conditioned media (CM) from these cell lines were tested for erythroid burst- promoting activity (BPA) and granulocyte colony-stimulating activity (CSA). BPA was detected in CM from 3/6 cultures of T-ALL patients and 4/6 CTCL cultures. CSA was found in the CM from 6/8 cultures of T-ALL patients, 7/12 CTCL cultures, and 3/4 CTCL cell lines that become independent of exogenous TCGF for growth. The CSA from several of the neoplastic T-cell cultures stimulated high levels of eosinophil colonies, a possible source of the eosinophilia seen in these patients. The ability of continuously proliferating human T lymphocytes, which retain functional specificity and responsiveness to normal humoral regulation, to produce factors that directly or indirectly stimulate myeloid and erythroid colony formation lends further credence to the role of T lymphocytes in regulating hematopoiesis.     

Recovery of T cell subsets after autologous bone marrow transplantation is mainly due to proliferation of mature T cells in the graft

In 22 patients with malignancies, treated with high-dose chemoradiotherapy and autologous bone marrow transplantation (BMT), peripheral blood T cell subsets and functions were studied. In ten cytomegalovirus (CMV)-negative patients, CD4+ and CD8+ T cells (representing T cells of the helper/inducer phenotype and T cells of the suppressor/cytotoxic phenotype, respectively), recovered slowly and simultaneously. In 12 CMV-positive patients, however, CD8+ T cells recovered more rapidly than CD4+ T cells and rose to increased counts. No T cells with an immature phenotype (CD1+, OKT6+) were observed. Lymphocyte stimulation by herpes simplex virus infected fibroblasts (and by CMV-infected fibroblasts in CMV-positive patients) in contrast remained high and even increased after BMT in both groups. These data indicate that T cell recovery after autologous BMT is mainly due to proliferation of mature T cells present in the BM graft and not to generation of new T cells from T cell precursors.     

High-dose etoposide and cyclophosphamide without bone marrow transplantation for resistant hematologic malignancy

Seventy-five patients with resistant acute leukemia or lymphoma received high-dose cyclophosphamide and etoposide to explore the activity of this combination in resistant hematologic malignancies, and to determine the maximum doses of these drugs that can be combined without bone marrow transplantation. Etoposide was administered over 29 to 69 hours by continuous infusion corresponding to total doses of 1.8 g/m2 to 4.8 g/m2. Cyclophosphamide, 50 mg/kg/d, was administered on 3 or 4 consecutive days total 150 to 200 mg/kg ideal body weight). At all dose levels myelosuppression was severe but reversible. Mucosal toxicity was dose-limiting with the maximum tolerated dose level combining etoposide 4.2 g/m2 with cyclophosphamide 200 mg/kg. Continuous etoposide infusion produced stable plasma levels that were lower than would be achieved after administration by short intravenous infusion, and this could explain our ability to escalate etoposide above the previously reported maximum tolerated dose. There were 28 complete (35%) and 12 partial (16%) responses. Median duration of complete response (CR) was 3.5 months (range 1.1 to 20+). Seventeen of 40 patients (42%) with acute myelogenous leukemia (AML) achieved CR, including 6 of 20 (30%) with high-dose cytosine arabinoside resistance. We conclude that bone marrow transplantation is not required after maximum tolerated doses of etoposide and cyclophosphamide. This regimen is active in resistant hematologic neoplasms, and the occurrence of CR in patients with high-dose cytosine arabinoside-resistant AML indicates a lack of complete cross-resistance between these regimens.