Id1 and Id3 are required for neurogenesis, angiogenesis and vascularization of tumour xenografts

Id proteins may control cell differentiation by interfering with DNA binding of transcription factors. Here we show that targeted disruption of the dominant negative helix-loop-helix proteins Id1 and Id3 in mice results in premature withdrawal of neuroblasts from the cell cycle and expression of neural-specific differentiation markers. The Id1-Id3 double knockout mice also display vascular malformations in the forebrain and an absence of branching and sprouting of blood vessels into the neuroectoderm. As angiogenesis both in the brain and in tumours requires invasion of avascular tissue by endothelial cells, we examined the Id knockout mice for their ability to support the growth of tumour xenografts. Three different tumours failed to grow and/or metastasize in Id1+/- Id3-/- mice, and any tumour growth present showed poor vascularization and extensive necrosis. Thus, the Id genes are required to maintain the timing of neuronal differentiation in the embryo and invasiveness of the vasculature. Because the Id genes are expressed at very low levels in adults, they make attractive new targets for anti-angiogenic drug design.

Recombinant human granulocyte colony-stimulating factor. Effects on hematopoiesis in normal and cyclophosphamide-treated primates

We examined the in vivo effects of recombinant human granulocyte colony-stimulating factor (rhG-CSF) in primates (cynomolgus monkeys) treated with subcutaneous doses of rhG-CSF for 14-28 d. A dose-dependent increase in the peripheral white blood cells (WBC) was seen, reaching a plateau after 1 wk of rhG-CSF treatment. The elevation of WBC was due to an increase in the absolute neutrophil count. These results demonstrate that rhG-CSF is a potent granulopoietic growth and differentiation factor in vivo. In cyclophosphamide (CY)-induced myelosuppression, rhG-CSF was able to shorten the time period of WBC recovery in two treated monkeys to 1 wk, as compared to more than 4 wk for the control monkey. Its ability to significantly shorten the period of chemotherapy-induced bone marrow hypoplasia may allow clinicians to increase the frequency or dosage of chemotherapeutic agents. In addition, the increase in absolute numbers of functionally active neutrophils may have a profound effect in the rate and severity of neutropenia-related sepsis. Furthermore, the activities reported here indicate a potential role for rhG-CSF in the treatment of patients with myelodysplastic syndrome, congenital agranulocytosis, radiation-induced myelosuppression, and bone marrow transplantation.

Transplantation for acute leukaemia with HLA-A and B nonidentical parental marrow cells fractionated with soybean agglutinin and sheep red blood cells

A new procedure for enrichment of marrow precursors and removal of T lymphocytes from large volumes of human bone marrow, involving initial differential agglutination of T lymphocytes and mature marrow elements with soybean agglutinin, followed by rosetting with sheep red blood cells, was used to fractionate marrow cells from an HLA-A, B, DR non-identical, MLC non-reactive, paternal donor for transplantation into an infant with acute leukaemia. This transplant became completely engrafted and resulted in full recovery of normal, donor-derived haematopoietic function without graft-versus-host disease, sustained for 11 weeks after transplantation, at which time the patient's leukaemia recurred. Subsequently, the patient received chemotherapy and achieved a remission with regeneration of normal marrow cells of donor origin. The patient's course demonstrated the potential of lectin-separated marrow grafts to restore durable haematopoiesis, without graft versus host disease, in a lethally irradiated allogeneic host.

Biology and adoptive cell therapy of Epstein-Barr virus-associated lymphoproliferative disorders in recipients of marrow allografts

Epstein-Barr virus (EBV) is an ubiquitous herpesvirus which is carried as a latent infection of B lymphocytes and salivary gland epithelial cells in over 90% of normal adults. Latently infected EBV-transformed B cells circulate at low frequency in the blood for the life of the host. These transformed B cells stimulate a heterogeneous and complex host cell response, ultimately leading to the development and maintenance of high frequencies of HLA-restricted T cells specific for the EBV-encoded nuclear antigens EBNA2-EBNA6 and the latency membrane proteins LMP-1 and LMP-2. Responses to latent EBV-encoded proteins are hierarchical with responses to certain epitopes predominating, dependent upon the HLA genotype of the host. Profound suppression of T-cell immunity may permit the emergence of polyclonal, oligoclonal or monoclonal EBV antigen-expressing lymphoproliferative disorders or malignant B-cell lymphomas expressing these latent EBV antigens. Adoptive transfer of small numbers of peripheral blood mononuclear cells or HLA-partially matched T cells from in vitro expanded EBV-specific T-cell lines derived from a seropositive marrow donor has induced durable regressions of bulky, widely metastatic monoclonal EBV lymphomas in a high proportion of cases. This review describes the current state of knowledge and hypothesis regarding the biology and immunology of EBV infection in the normal host, the features of donor, host and virus which contribute to the development of EBV-associated lymphoproliferative diseases and the mechanisms whereby they are controlled by adoptive transfer of immune T cells.

Allogeneic bone marrow transplantation after hyperfractionated total-body irradiation and cyclophosphamide in children with acute leukemia

Ninety-seven children with either acute lymphoblastic leukemia (ALL) or acute myelogenous leukemia (AML) received HLA-identical bone marrow transplants from sibling donors, after preparation with 1320 cGy of hyperfractionated total-body irradiation and high-dose cyclophosphamide. Kaplan-Meier product-limit estimates (means +/- SE) of disease-free survival at five years among patients with ALL in second remission, third remission, and fourth remission or relapse were 64 +/- 9, 42 +/- 14, and 23 +/- 11 percent, respectively, with probabilities of relapse of 13 +/- 7, 25 +/- 13, and 64 +/- 16 percent. Among patients with AML in first remission, second remission, and third remission or relapse, five-year disease-free survival estimates were 66 +/- 10, 75 +/- 15, and 33 +/- 19 percent, with respective relapse probabilities of 0, 13 +/- 12, and 67 +/- 19 percent. The most frequent cause of death in patients in early remission (ALL in second or third remission or AML in first or second remission) was bacterial sepsis, fungal sepsis, or both, most often in the presence of acute or chronic graft-versus-host disease. Among patients with ALL who received transplants while in second remission, the duration of the initial remission had no effect on the probability of relapse after transplantation. The only pretransplantation factor that significantly affected outcome was the disease status at the time of transplantation; patients in early remission had better disease-free survival. We conclude that transplantation after preparation with hyperfractionated total-body irradiation and cyclophosphamide is an effective mode of therapy in children with refractory forms of acute leukemia.

Reconstitution in severe combined immunodeficiency by transplantation of marrow from an unrelated donor

A patient with severe combined immunodeficiency received seven transplants of bone marrow from an HLA-B-compatible and HLA-D-compatible unrelated donor in an attempt to provide immunologic reconstitution. The first four transplants achieved restricted engraftment with evidence of rudimentary immunologic function. A fifth transplant, given after low-dose cyclophosphamide, produced reconstituion of cell-mediated immunity. Marrow aplasia developed after recontamination with a nonpathogenic microflora. Transplantation of marrow previously stored in liquid nitrogen was ineffective. A subsequent transplant, administered after high-dose cyclophosphamide, achieved durable engraftment, with complete hematopoietic and immunologic reconstitution. Seventeen months after transplantation, full functional engraftment persists. Graft-versus-host disease has been chronic and moderately severe, but limited to the skin and oral mucosa. Transplantation of marrow from unrelated histocompatible donors may provide a useful treatment for patients with severe combined immunodeficiency or aplastic anemia who lack a matched sibling or related donor.

Prevention of cytomegalovirus infection by prophylaxis with an intravenous, hyperimmune, native, unmodified cytomegalovirus globulin. Randomized trial in bone marrow transplant recipients

We have completed a randomized trial to evaluate the safety and effectiveness of hyperimmune cytomegalovirus intravenous human globulin in prevention of cytomegalovirus infection and related problems in bone marrow transplant recipients. Prophylactic intravenous administration of this native, intact, hyperimmune, cytomegalovirus IgG, at a dose of 200 mg/kg 25, 50, and 75 days following transplant resulted in complete protection against cytomegalovirus infection during the 120 days covered by the treatment (p = 0.009). There was no interstitial pneumonia or mortality in the group receiving the hyperimmune IgG. This is significant at the p = 0.014 when compared with the supporting treatment control group. In bone marrow transplant recipients, prophylaxis with a total dosage of 0.6 g/kg of an intravenous hyperimmune cytomegalovirus globulin was safe and afforded effective protection against cytomegalovirus infection and interstitial pneumonia in this high-risk population.

Invasive adenoviral infections in T-cell-depleted allogeneic hematopoietic stem cell transplantation: high mortality in the era of cidofovir

BACKGROUND

Adenovirus (ADV) infection occurs in 5-21% of allogeneic hematopoietic stem cell transplants (HSCT). Symptomatic enteritis and hemorrhagic cystitis may be encountered but are seldom fatal. In contrast, mortality rates of up to 75% are reported for adenoviral pneumonia or hepatitis. Cidofovir is currently being increasingly used for treatment of adenoviral infections after HSCT. The efficacy of cidofovir in patients with invasive adenoviral infection is not established.

FINDINGS

We reviewed 687 adult and pediatric patients who received allogeneic HSCT at our institution from 1998 through June 2005. ADV was isolated from 64 (9.3%) patients. Eleven patients received cidofovir for invasive disease occurring at median 39 days (range 3-145) post HSCT. The median age was 40 (range 6-61) years. Seventy-three percent received a T-cell-depleted graft and 18% had grade 3-4 graft-versus-host disease (GVHD) of the gut. Three out of 3 (100%) patients with adenoviral pneumonia died. One patient with hepatitis, cholecysitis, and viremia cleared the infection after 3 months. Two out of 7 (28.6%) patients with hemorrhagic colitis or cystitis died of ADV (1 with extensive GVHD).

CONCLUSION

Mortality rates of ADV pneumonitis after allogeneic HSCT remain high in the era of cidofovir. Clinical trials are needed to evaluate management strategies for this life-threatening infection.

Hyperfractionated total body irradiation for bone marrow transplantation. Results in seventy leukemia patients with allogeneic transplants

From May, 1979 to March, 1981, 76 leukemia patients were prepared for bone marrow transplantation (BMT) with a new hyperfractionated total body irradiation (TBI) regimen (1320 cGy in 11 fractions, 3x/day), followed by cyclophosphamide, 60 mg/kg, for two days. Partial lung shielding was done on each treatment, with supplemental electron beam treatments of the chest wall to compensate, and of the testes, a sanctuary site. This regimen was initiated to potentially reduce fatal interstitial pneumonitis as well as decrease leukemic relapse. These patients were analyzed in May, 1982, for a minimum follow-up of 14 months. Overall actuarial survival at 1 year for acute non-lymphocytic leukemia (ANLL) patients is 63%, while relapse-free survival at 1 year is 53%. For those ANLL patients who underwent BMT while in remission (first, second, and third combined), relapse-free survival is 61% at 1 year compared with 40% for those patients who had their BMT at the time of relapse (greater than or equal to 10% blasts in marrow). On the other hand, for acute lymphocytic leukemia (ALL) patients, there is no significant difference between relapse or remission patients with regard to overall survival or relapse-free survival, when relapse is defined as greater than 5% blasts in the marrow at the time of cytoreduction. Overall actuarial survival at 1 year for ALL is 61% and relapse-free survival is 45% at 1 year. Patients with ALL who had their BMT cytoreduction at the time of relapse have a survival equal to that of our remission patients, and greater than that of patients in relapse cytoreduced with a single dose as reported by others. However, patients with greater than or equal to 10% blasts have not fared as well, having only a 22% 1 year relapse-free survival compared with a 68% 1 year relapse-free survival for patients with less than 10% blasts. Fatal interstitial pneumonitis has dropped to 18% compared with 50% in our previous single-dose TBI regimen (1000 cGy), in which the same doses of cyclophosphamide were given prior to TBI. In conclusion, not only has fatal interstitial pneumonitis been reduced by hyperfractionation and partial lung blocking, but there may be a survival advantage in ALL patients in relapse, who have a survival equal to that of remission patients. This may indicate a greater cell kill with the higher dose (1320 cGy) attained with this regimen, in these patients with a higher leukemic cell burden.

Epigenetic contributors to the discordance of monozygotic twins

Human monozygotic (MZ) twins estimated to occur once in 250 live births, result from an errant decision by embryonic cell(s) to develop as separate embryos. They are considered genetically identical and any phenotypic discordance between them has been used to implicate the role of environment. More recent literature, however, has questioned these assumptions but the frequency and the nature of any genetic discordance between MZ twins remains poorly understood. We will review published cases of phenotypic and genetic discordance between monozygotic twins to argue that not all discordance between such twins is due to differences in environment. The causes of reduced concordance between MZ twins remains poorly understood. They represent among the challenging aspects of the genetics of complex multi-factorial traits and diseases. A number of questions regarding the published results on MZ twins merit a re-assessment in the light of modern molecular insight of the human genome. Such an assessment is needed in directing future studies on MZ twins. In particular, we will deal with the origin, development, genetic and epigenetic factors that may have implications in discordance of the MZ twin pairs.

N7: a novel multi-modality therapy of high risk neuroblastoma (NB) in children diagnosed over 1 year of age

BACKGROUND

The N7 protocol for poor-risk neuroblastoma uses dose-intensive chemotherapy (as in N6 protocol [Kushner et al.: J Clin Oncol 12:2607-2613, 1994] but with lower dosing of vincristine) for induction, surgical resection and 2100 cGy hyperfractionated radiotherapy for local control, and for consolidation, targeted radioimmunotherapy with 131I-labeled anti-GD2 3F8 monoclonal antibody and immunotherapy with unlabeled/unmodified 3F8 (400 mg/m2).

PROCEDURE

The chemotherapy consists of: cyclophosphamide 70 mg/kg/d x 2 and a 72-hr infusion of doxorubicin 75 mg/m2 plus vincristine 2 mg/m2, for courses 1, 2, 4, and 6; and cisplatin 50 mg/m2/d x 4 and etoposide 200 mg/m2/d x 3, for courses 3, 5, and 7. 131I-3F8 is dosed at 20 mCi/kg, which is myeloablative and therefore necessitates stem-cell support.

RESULTS

Of the first 24 consecutive previously untreated patients more than 1 year old at diagnosis, 22 were stage 4 and two were unresectable stage 3 with MYCN amplification. Chemotherapy achieved CR/VGPR in 21 of 24 patients. Twenty patients to date have completed treatment with 131I-3F8, and 15 patients have completed all treatment. With a median follow-up of 19 months, 18 of 24 patients remain progression-free.

CONCLUSIONS

Major toxicities were grade 4 myelosuppression and mucositis during chemotherapy, and self-limited pain and urticaria during antibody treatment. Late effects include hearing deficits and hypothyroidism.

Circulating polyribophosphate in Hemophilus influenzae, type b meningitis. Correlation with clinical course and antibody response

In systemic infections caused by Hemophilus influenzae, type b, the capsular polysaccharide, polyribophosphate, is released into the circulation. Polyribophosphate was quantitated in serial serum and cerebrospinal fluid samples from 45 children with H. influenzae, type b meningitis by means of a radiolabeled antigen-binding inhibition assay. Polyribophosphate was regularly found in acute serum and cerebrospinal fluid samples and could be detected in unbound form for periods of 1-30 days after initiation of effective therapy. Complexes of polyribophosphate dissociable with acid and pepsin were detected in serum samples from 17 patients, in one case for a period of 145 days after hospitalization. Polyribophosphate levels and patterns of clearance were studied in relation to hospital course and antibody response. Patients with prolonged antigenemia had protracted fevers and severe neurological symptoms during hospitalization, frequently with focal complications.Antipolyribophosphate antibody responses were detected during the first 100 days of convalescence by radioimmunoassay in 79% of the patients studied, including 60% of the children 1 yr or less in age. The intensity of antibody response although clearly related to the age of the patient, was more reliably predicted by the efficiency of antigen clearance. Antibody responses were uniformly of low magnitude in patients with prolonged antigenemia, irrespective of age. Paients who failed to develop antibody to polyribophosphate after meningitis also exhibited impaired antigen clearance. These studies suggest that mechanisms necessary for clearance of polyribophosphate may influence the development and intensity of the humoral immune response and raise the possibility of developmental deficiencies in the clearance system in infants and children.

Phenylbutazone-warfarin interaction in man: further stereochemical and metabolic considerations

The pharmacokinetics and urinary metabolic profile of R and S-warfarin, following administration of a 1.5 mg/kg oral dose of racemic warfarin, alone and 4 days into an oral regimen of 100 mg phenylbutazone three times a day, was investigated in three volunteers using a stereospecific h.p.l.c. fluorescent assay. The mean elimination half-life of S-warfarin was increased from 25 to 46 h during phenylbutazone administration, whilst that of the R-isomer was decreased from 37 to 25 h. The peak unbound concentrations of both warfarin enantiomers were higher during phenylbutazone administration, due to displacement. Displacement was not stereoselective. The unbound clearance of more potent S-warfarin is decreased by four-fold during phenylbutazone administration, due to substantial inhibition of both 6- and 7-hydroxylation, significant pathways of elimination of S-warfarin in the absence of phenylbutazone. The unbound clearance of R-warfarin is almost unchanged during phenylbutazone administration, due to the marginal effect of phenylbutazone on 6- and 7-hydroxylation, themselves minor pathways of elimination of this enantiomer in the absence of phenylbutazone. The stereoselective reduction of S- and R-warfarin, to their respective SS and RS-alcohols, is also substantially inhibited during phenylbutazone administration. Collectively the data point to the complex effect of phenylbutazone administration on warfarin's pharmacokinetics.

Marrow transplantation for juvenile osteopetrosis

Two children with the juvenile form of osteopetrosis were treated with marrow transplants from their HLA identical siblings. Following transplantation each child exhibited extensive bone reabsorption with a marked augmentation of osteoclastic function attributable to donor osteoclasts, including remodeling of bone with expansion of intramedullary hematopoiesis and correction of associated abnormalities of thymic factor and natural killer cells. Osteopetrosis ultimately recurred in one patient in whom engraftment of donor hematopoietic elements was not achieved. Our studies indicate that marrow transplantation will correct osteopetrosis but that permanent reconstitution necessitates sustained engraftment of marrow precursors of cells with osteoclastic activity.

Human Epstein-Barr virus (EBV)-specific cytotoxic T lymphocytes home preferentially to and induce selective regressions of autologous EBV-induced B cell lymphoproliferations in xenografted C.B-17 scid/scid mice

C.B-17 scid/scid (severe combined immunodeficiency [SCID]) mice inoculated with peripheral blood lymphocytes from Epstein-Barr virus (EBV)-seropositive donors, or with EBV-transformed lymphoblastoid B cell lines (EBV-LCL), develop lethal human EBV+ B cell lymphoproliferative disorders (EBV-LPD) with characteristics similar to those arising in immunodeficient patients. Using this model, we examined the capacity of human effector cells to control human EBV-LPD. SCID mice received rabbit anti-asialo GM1 antiserum to abrogate endogenous natural killer-cell function. Preliminary experiments showed that adoptive transfer of peripheral blood mononuclear cells (PBMC), purified T cells, interleukin (IL) 2-activated PBMC or anti-CD3-activated T cells derived from EBV-seropositive donors did not result in improved survival of treated mice (in vivo effector/target ratio 2:1 to 1:1). In contrast, EBV-specific cytotoxic T lymphocytes (CTL), derived from EBV-seropositive donors and expanded in vitro, exhibited strong EBV-specific and HLA-restricted activity both in vitro and in vivo. SCID mice inoculated intraperitoneally with autologous but not with HLA-mismatched EBV-LCL had significantly improved survival relative to untreated mice after inoculation of EBV-specific CTL either intraperitoneally (P<0.001) or intravenously (P<0.001) (in vivo effector/target ratio 1:1). SCID mice bearing large subcutaneous EBV+ tumors and treated intravenously with 10(7) EBV-specific CTL achieved complete tumor regression. Both CTL- and CTL-plus-IL-2-treated mice survived significantly longer than untreated animals or animals treated with IL-2 alone (P = 0.0004 and P<0.02, respectively). SCID mice bearing two subcutaneous EBV+ tumors, one autologous and the other HLA mismatched to the EBV-specific CTL donor, had regression of only the autologous tumor after intravenous infusion of 10(7) EBV-specific CTL. Moreover, we could demonstrate preferential homing of PKH26-labeled EBV-specific CTL to autologous but not to HLA-mismatched EBV+ tumors as early as 24 h after intravenous adoptive transfer. Immunophenotypic analyses also demonstrated preferential infiltration of T cells into the autologous EBV+ tumor in SCID mice bearing both the autologous and either fully HLA-mismatched or genotypically related haplotype-sharing EBV+ tumors. The human T cells infiltrating EBV+ tumors were CD3+ and, predominantly, CD8+CD4-. Our results indicate that EBV-specific CTL preferentially localize to and infiltrate EBV+ tumors bearing the appropriate HLA antigens and thereafter induce targeted regressions of disease.

Stereochemical aspects of warfarin drug interactions: use of a combined pharmacokinetic-pharmacodynamic model

OBJECTIVE

To apply a combined pharmacokinetic-pharmacodynamic model to data from warfarin drug interaction studies.

METHODS

The pharmacokinetic model for warfarin enantiomers combined a common first-order absorption process with individual clearance and volume of distribution values and is based on unbound drug. The complete pharmacodynamic model comprised two components: that involving inhibition of prothrombin complex activity (PCA) synthesis described by a sigmoid maximum effect (Emax) model and that relating temporal changes in PCA to synthesis and degradation. The combined model was applied to prothrombin time and plasma concentration-time data obtained after oral administration of single doses of racemic warfarin to healthy subjects either alone or during multiple dosing with the metabolic enzyme inhibitor phenylbutazone or the inducer secobarbital.

RESULTS

The five parameters associated with the complete pharmacodynamic model were kd (0.054 +/- 0.014 hr-1), the degradation rate constant of PCA; Cu50,S (0.0026 +/- 0.0015 mg.L-1) and Cu50,R (3.45 +/- 4.20 mg.L-1), the unbound concentrations of (S)- and (R)-warfarin required to produce a 50% reduction in PCA synthesis if administered individually; gamma (0.90 +/- 0.23), the slope parameter in the sigmoid Emax model; and td (8.2 +/- 0.3 hours), the observed delay in the onset of warfarin anticoagulant response.

CONCLUSIONS

These findings qualitatively confirm the known potency difference between warfarin enantiomers. Furthermore, although phenylbutazone and secobarbital altered the pharmacokinetics of warfarin, these compounds do not appear to influence its pharmacodynamics. Simulation studies indicate that, after racemate administration, the continual presence of the more potent (S)-enantiomer precludes accurate assessment of Cu50,R. Analysis indicates that use of racemic (rather than enantiomer) warfarin concentration data in drug interaction studies may lead to misinterpretation of pharmacodynamic data.

Cytoreduction with iodine-131-anti-CD33 antibodies before bone marrow transplantation for advanced myeloid leukemias

The monoclonal antibodies M195 and HuM195 target CD33, a glycoprotein found on myeloid leukemia cells. When labeled with iodine-131 ((131)I), these antibodies can eliminate large disease burdens and produce prolonged myelosuppression. We studied whether (131)I-labeled M195 and HuM195 could be combined safely with busulfan and cyclophosphamide (BuCy) as conditioning for allogeneic BMT. A total of 31 patients with relapsed/refractory acute myeloloid leukemia (AML) (n=16), accelerated/myeloblastic chronic myeloid leukemia (CML) (n=14), or advanced myelodysplastic syndrome (n=1) received (131)I-M195 or (131)I-HuM195 (122-437 mCi) plus busulfan (16 mg/kg) and cyclophosphamide (90-120 mg/kg) followed by infusion of related-donor bone marrow (27 first BMT; four second BMT). Hyperbilirubinemia was the most common extramedullary toxicity, occurring in 69% of patients during the first 28 days after BMT. Gamma camera imaging showed targeting of the radioisotope to the bone marrow, liver, and spleen, with absorbed radiation doses to the marrow of 272-1470 cGy. The median survival was 4.9 months (range 0.3-90+ months). Three patients with relapsed AML remain in complete remission 59+, 87+, and 90+ months following bone marrow transplantation (BMT). These studies show the feasibility of adding CD33-targeted radioimmunotherapy to a standard BMT preparative regimen; however, randomized trials will be needed to prove a benefit to intensified conditioning with radioimmunotherapy.

Affinity maturation of T-cell receptor-like antibodies for Wilms tumor 1 peptide greatly enhances therapeutic potential

WT1₁₂₆ (RMFPNAPYL) is a human leukocyte antigen-A2 (HLA-A2)-restricted peptide derived from Wilms tumor protein 1 (WT1), which is widely expressed in a broad spectrum of leukemias, lymphomas and solid tumors. A novel T-cell-receptor (TCR)-like single-chain variable fragment (scFv) antibody specific for the T-cell epitope consisting of the WT1/HLA-A2 complex was isolated from a human scFv phage library. This scFv was affinity-matured by mutagenesis combined with yeast display and structurally analyzed using a homology model. This monovalent scFv showed a 100-fold affinity improvement (dissociation constant (K_D)=3 nm) and exquisite specificity towards its targeted epitope or HLA-A2⁺/WT1⁺ tumor cells. Bivalent scFv-huIgG1-Fc fusion protein demonstrated an even higher avidity (K_D=2 pm) binding to the T-cell epitope and to tumor targets and was capable of mediating antibody-dependent cell-mediated cytotoxicity or tumor lysis by chimeric antigen receptor-expressing human T- or NK-92-MI-transfected cells. This antibody demonstrated specific and potent cytotoxicity in vivo towards WT1-positive leukemia xenograft that was HLA-A2 restricted. In summary, T-cell epitopes can provide novel targets for antibody-based therapeutics. By combining phage and yeast displays and scFv-Fc fusion platforms, a strategy for developing high-affinity TCR-like antibodies could be rapidly explored for potential clinical development.

No retroviremia or pathology in long-term follow-up of monkeys exposed to a murine amphotropic retrovirus

Four monkeys were exposed to a retroviral vector and replication-competent murine amphotropic retrovirus in a bone marrow transplantation/gene transfer protocol (Kantoff et al., 1987). We have studied these animals 2 and 3 years post-transplantation and did not detect replicating virus in serum, peripheral blood mononuclear cells, or bone marrow cells. Amphotropic envelope sequences could not be detected in blood or bone marrow cells by Southern blotting or the polymerase chain reaction. Antibodies directed against the p30 and gp70 viral antigens were detected by Western blot and immunoprecipitation. The animals remain alive and well. Our findings suggest that primates can clear murine amphotropic retroviruses even when exposure occurs during a time of severe immunosuppression.

Absence of interleukin 2 production in a severe combined immunodeficiency disease syndrome with T cells

We have characterized a child with a severe combined immunodeficiency disease syndrome with increased numbers, but a normal distribution, of CD3+ T cells. This patient's immunological defect appears to be attributable to a selective deficiency in T cell production of IL-2, which may reflect a subtle abnormality in the IL-2 gene locus or a defect in a regulatory factor necessary for IL-2 transcription. The increased numbers of phenotypically normal T cells in this patient suggest that alternative pathways of T cell development exist in man or that IL-2 production intra- and extrathymically is controlled via distinct regulatory mechanisms.

ABH incompatible bone marrow transplantation: removal of erythrocytes by starch sedimentation

Nineteen patients with acute leukaemia underwent bone marrow transplantation despite major ABH incompatibility between donor and recipient. The marrow inoculum was prepared prior to infusion by admixture with hydroxyethyl starch to sediment the incompatible erythrocytes, which were then discarded. The infusion was well tolerated with two patients developing transient haemoglobinuria, seven patients developing low grade fever and 10 experiencing no reaction. Durable haematopoietic engraftment was achieved in the 18 evaluable patients and was not influenced by pre-transplant isohaemagglutinin titres. No difference in time to engraftment, incidence of GVHD or in overall survival was found, compared to ABH compatible transplants. Therefore, the presence of incompatibility did not appear to influence transplant outcome adversely. The technique described is a rapid and safe method for overcoming the ABH barrier in marrow transplantation.