Only strongly enhanced residual FDG uptake in early response PET (Deauville 5 or qPET ≥ 2) is prognostic in pediatric Hodgkin lymphoma: Results of the GPOH-HD2002 trial

PURPOSE

In 2014, we published the qPET method to quantify fluorodeoxyglucose positron emission tomography (FDG-PET) responses. Analysis of the distribution of the quantified signals suggested that a clearly abnormal FDG-PET response corresponds to a visual Deauville score (vDS) of 5 and high qPET values ≥ 2. Evaluation in long-term outcome data is still pending. Therefore, we analyzed progression-free survival (PFS) by early FDG-PET response in a subset of the GPOH-HD2002 trial for pediatric Hodgkin lymphoma (PHL).

PATIENTS/METHODS

Pairwise FDG-PET scans for initial staging and early response assessment after two cycles of chemotherapy were available in 93 PHL patients. vDS and qPET measurement were performed and related to PFS.

RESULTS

Patients with a qPET value ≥ 2.0 or vDS of 5 had 5-year PFS rates of 44%, respectively 50%. Those with qPET values < 2.0 or vDS 1 to 4 had 5-year PFS rates of 90%, respectively 80%. The positive predictive value of FDG-PET response assessment increased from 18% (9%; 33%) using a qPET threshold of 0.95 (vDS ≤ 3) to 30% (13%; 54%) for a qPET threshold of 1.3 (vDS ≤ 4) and to 56% (23%; 85%) when the qPET threshold was ≥ 2.0 (vDS 5). The negative predictive values remained stable at ≥92% (CI: 82%; 98%).

CONCLUSION

Only strongly enhanced residual FDG uptake in early response PET (vDS 5 or qPET ≥ 2, respectively) seems to be markedly prognostic in PHL when treatment according to the GPOH-HD-2002 protocol is given.

Consensus of German transplant centers on hematopoietic stem cell transplantation in Fanconi anemia

Allogeneic hematopoietic stem cell transplantation (HSCT) is currently the only curative therapy for the severe hematopoietic complications associated with Fanconi anemia (FA). In Germany, it is estimated that 10-15 transplants are performed annually for FA. However, because FA is a DNA repair disorder, standard conditioning regimens confer a high risk of excessive regimen-related toxicities and mortality, and reduced intensity regimens are linked with graft failure in some FA patients. Moreover, development of graft-versus-host disease is a major contributing factor for secondary solid tumors. The relative rarity of the disorder limits HSCT experience at any single center. Consensus meetings were convened to develop a national approach for HSCT in FA. This manuscript outlines current experience and knowledge about HSCT in FA and, based on this analysis, general recommendations reached at these meetings.

Allogeneic hematopoietic stem cell transplantation in solid organ transplant recipients: a retrospective, multicenter study of the EBMT

We conducted a questionnaire survey of the 565 European Society for Blood and Marrow Transplantation centers to analyze the outcome of allogeneic hematopoietic stem cell transplantation (alloSCT) in recipients of solid organ transplantation (SOT). We investigated 28 patients with malignant (N = 22) or nonmalignant diseases (N = 6), who underwent 31 alloSCT procedures: 12 after kidney, 13 after liver and 3 after heart transplantation. The incidence of solid organ graft failure at 60 months after first alloSCT was 33% (95% confidence interval [CI], 16-51%) for all patients, 15% (95% CI, 2-40%) for liver recipients and 50% (95% CI, 19-75%) for kidney recipients (p = 0.06). The relapse rate after alloSCT (22%) was low following transplantation for malignant disorders, despite advanced stages of malignancy. Overall survival at 60 months after first alloSCT was 40% (95% CI, 19-60%) for all patients, 51% (95% CI, 16-86%) for liver recipients and 42% (95% CI, 14-70%) for kidney recipients (p = 0.39). In summary, we show that selected SOT recipients suffering from hematologic disorders may benefit from alloSCT and experience enhanced long-term survival without loss of organ function.

Pharmacokinetic monitoring of intravenous cyclosporine A in pediatric stem-cell transplant recipients. The trough level is not enough

In order to monitor CsA serum levels after SCT, trough levels (C0) are widely used. The aim of this study was to estimate the population and individual PK parameters for patients receiving intravenous CsA after SCT. In 27 pediatric patients after SCT receiving CsA (3 mg/kg/day) every 12 h, a total of 289 CsA concentrations was obtained. To describe the PK parameters of CsA, a two-compartment model with first order elimination was used. Covariate analysis identified body weight, age, and the co-administration with itraconazole and tobramycine as factors influencing the Cl. The statistical comparison of AUC, trough level, and C2 indicates a correlation between AUC and C2, but no correlation between the AUC and C0, r = 0.24 (p = 0.146) vs. r = 0.526 (p = 0.000692), respectively. Our results underscore the fact that CsA trough levels do not reflect the drug exposure in patients receiving intravenous CsA after SCT. By contrast, CsA blood levels measured 2-6 h after CsA infusion showed a better correlation with the AUC. Our data provide new information to optimize the balancing act between GvHD-prophylaxis, graft vs. leukemia effect, and CsA side-effects after SCT.

Relapse, not regimen-related toxicity, was the major cause of treatment failure in 11 children with Down syndrome undergoing haematopoietic stem cell transplantation for acute leukaemia

We report a retrospective analysis of 11 children with Down syndrome (DS) treated by SCT in eight German/Austrian SCT centres. Indications for transplantation were acute lymphoblastic leukaemia (N=8) and acute myeloid leukaemia (N=3). A reduced intensity conditioning (RIC) containing 2 Gy TBI was given to two patients, another five received a myeloablative regimen with 12 Gy TBI. Treosulphan or busulphan was used in the remaining four children. Four of eleven (36%) patients are alive. All of them were treated with a myeloablative regimen. One of the four surviving children relapsed 9 months after SCT and is currently receiving palliative outpatient treatment. The main cause of death was relapse (5/11). Two children died of regimen-related toxicity (RRT), one from severe exfoliative dermatitis and multiorgan failure after a treosulphan-containing regimen, the other from GvHD-related infections after RIC. Acute GvHD of the skin was observed in 10 of 10 evaluable patients, and chronic GvHD in 4 of 8. Our data show that DS patients can tolerate commonly used, fully myeloablative preparative regimens. The major cause of death is relapse rather than RRT resulting in an event-free survival of 18% and over all survival of 36%.

Outcomes of hematopoietic stem cell transplantation for Hurler's syndrome in Europe: a risk factor analysis for graft failure

Hurler's syndrome (HS), the most severe form of mucopolysaccharidosis type-I, causes progressive deterioration of the central nervous system and death in childhood. Allogeneic stem cell transplantation (SCT) before the age of 2 years halts disease progression. Graft failure limits the success of SCT. We analyzed data on HS patients transplanted in Europe to identify the risk factors for graft failure. We compared outcomes in 146 HS patients transplanted with various conditioning regimens and grafts. Patients were transplanted between 1994 and 2004 and registered to the European Blood and Marrow Transplantation database. Risk factor analysis was performed using logistic regression. ‘Survival’ and ‘alive and engrafted’-rate after first SCT was 85 and 56%, respectively. In multivariable analysis, T-cell depletion (odds ratio (OR) 0.18; 95% confidence interval (CI) 0.04–0.71; P=0.02) and reduced-intensity conditioning (OR 0.08; 95% CI 0.02–0.39; P=0.002) were the risk factors for graft failure. Busulfan targeting protected against graft failure (OR 5.76; 95% CI 1.20–27.54; P=0.028). No difference was noted between cell sources used (bone marrow, peripheral blood stem cells or cord blood (CB)); however, significantly more patients who received CB transplants had full-donor chimerism (OR 9.31; 95% CI 1.06–82.03; P=0.044). These outcomes may impact the safety/efficacy of SCT for ‘inborn-errors of metabolism’ at large. CB increased the likelihood of sustained engraftment associated with normal enzyme levels and could therefore be considered as a preferential cell source in SCT for ‘inborn errors of metabolism’.

Intravenous and oral sequential itraconazole antifungal prophylaxis in paediatric stem cell transplantation recipients: a pilot study for evaluation of safety and efficacy

This single-centre, retrospective, observational pilot study was performed to evaluate the safety and efficacy of intravenous and oral itraconazole prophylaxis in paediatric haematopoietic stem cell transplantation (HCT). Study end-points were proven invasive fungal infection (IFI), survival, adverse reactions and graft-vs.-host disease (GVHD); 53 children and one young adult (median age 8.6 yr; range 0.4-18.3) transplanted between November 2001 and August 2004 were included in this study. Itraconazole was given intravenously from day +3 after HCT until oral medication became possible and continued until day +100 after HCT. Two proven new IFI in the itraconazole group (candidiasis, n = 1; aspergillosis, n = 1) were observed. After a median follow-up of 1.6 yr (0.3-6.1), six deaths (8%) were seen; 24 patients (45%) developed GVHD degree I-II, three children (6%) had GVHD degree III-IV. In 11 of 53 patients (21%), itraconazole prophylaxis was discontinued prematurely, mostly because of fever of unknown origin (n = 7). In total, 21 of 53 (40%) of the children had abnormal results of laboratory investigations during the prophylaxis. The results of this pilot study indicate that itraconazole prophylaxis during HCT in children is feasible and safe, despite abnormal laboratory results. The efficacy in terms of prevention of IFI, however, has to be addressed in a prospective large-scale study.

Complete substitution of cyclophosphamide by fludarabine and ATG in a busulfan-based preparative regimen for children and adolescents with beta-thalassemia

Children and adolescents with homozygous beta-thalassemia can be cured by transplantation of normal stem cells after eradication of the thalassemic hematopoietic system. In an attempt to achieve durable engraftment and to minimize regimen-related toxicity (RRT), we have initiated a fludarabine-based pilot protocol not containing cyclophosphamide. Between 1999 and 2004, five children with beta-thalassemia major were enrolled. Median age at transplantation was 11.5 years (range 4-14 years). Three patients received conditioning with fludarabine (30 mg/m2/day x 6), oral busulfan (3.5 mg/kg/day x 4), and ATG rabbit Fresenius (10 mg/kg/day x 4). Two children received intravenous busulfan instead of oral busulfan at a dose of 2 x 1.4 mg/kg/day x 4 days. All children were transplanted with a fresh bone marrow graft from an HLA-identical sibling. Mean cell doses given were 3.7 x 10(8) nucleated cells/kg BW (range 2.4-6.2 x 10(8)/kg). Overall, 5/5 patients achieved donor engraftment and are alive and well. No GVHD exceeding grade I was observed, and 2/5 children maintained donor chimerism at 100%. One patient maintains mixed hematopoietic donor chimerism being between 94 and 97% nearly 5 years after transplant.

The impact of cyclosporin A on acute graft-versus-host disease after allogeneic bone marrow transplantation in children and adolescents with acute lymphoblastic leukemia

Experimental and clinical data demonstrate an antileukemia effect of acute graft-versus-host disease (aGVHD). In all, 58 pediatric patients with acute lymphoblastic leukemia (ALL) who had received an allogeneic bone marrow transplant (BMT) at our institution were retrospectively analyzed for a correlation between the development of aGVHD and leukemic relapse. Probability of relapse after 5 (3) years was 13% (7%) in patients developing grade II-IV aGVHD vs 30% in patients with grade 0 or I aGVHD. There was a trend for a difference of the point estimates at 3 years, but no overall significance because of an unusual late relapse. Moreover, we analyzed the impact of cyclosporin A (CsA) on aGVHD in a subgroup of 22 children who had received a matched sibling donor (MSD) BMT. An increased dose of CsA within the first 2 weeks after BMT led to decreased occurrence and severity of aGVHD (P=0.035). The cumulative CsA dose appeared to have more impact than the average CsA whole-blood levels within the first 2 weeks and than the CsA dose given from day 15 to 40. In this subgroup, no life-threatening aGVHD or death from aGVHD occurred. In all cases (6/22), leukemic relapse was the cause of death. We therefore suggest that there is a relation between dose of CsA and relapse rate in childhood ALL transplanted from a MSD.

Non-radiotherapy conditioning with stem cell transplantation from alternative donors in children with refractory severe aplastic anemia

Conditioning including total body/lymphoid irradiation is widely used to prevent graft rejection in patients with refractory severe aplastic anemia (SAA) undergoing hemopoietic cell transplantation (HCT) from alternative donors and or after graft manipulation. To reduce regimen-related toxicity we transplanted three children with refractory SAA after conditioning with radiotherapy-free regimens. Conditioning included fludarabine 175-180 mg/m2 in all patients. In addition, patient 1 (failing two previous grafts) received thiotepa 10 mg/kg and Campath-1H 60 mg/m2; patient 2 cyclophosphamide 120 mg/kg, thiotepa 15 mg/kg and OKT-3 0.1 mg/kg/day for 4 weeks; and patient 3 cyclophosphamide 120 and ATG 90 mg/kg. Stem cell source was unmanipulated marrow from the same unrelated donor as for the two previous transplantations in patient 1 and CD34+-purified peripheral blood stem cells from an HLA-matched unrelated donor and from the haploidentical mother in patients 2 and 3. Only patient 1 received graft-versus-host disease (GVHD) prophylaxis with cyclosporine A and mycophenolate mofetil. Follow-up is now 30, 51, and 15 months. None of the patients developed GVHD. All patients have normal counts with complete donor chimerism. Fludarabine-based conditioning is powerfully immunosuppressive and may be used for children with refractory SAA undergoing HCT from alternative donors even after rejection following previous HCT.

Transplantation of allogeneic CD34-selected stem cells after fludarabine-based conditioning regimen for children with mucopolysaccharidosis 1H (M. Hurler)

Hurler syndrome (MPS1H) is a progressive inborn error of mucopolysaccharide metabolism leading to premature death. Allogeneic hematopoietic cell transplantation (HCT) can achieve stabilization and improve long-term survival. However, large studies have shown that preparative regimen-related toxicity (RRT) and graft failure rates have been relatively high. We transplanted five Hurler children with a fludarabine-based conditioning regimen, consisting of fludarabine/busulphan/ATG for matched family donor (MFD), with the addition of melphalan for mismatched family donor and matched unrelated donor (MUD) transplantations. Median age at HCT was 27 months (range 10-36). The source of stem cells was bone marrow in one MFD and CD34-selected PBSC in four patients. Median CD34+ cell dose was 25 x 10(6)/kg (range 11.5-54). No RRT > grade II was observed. All patients are surviving at a median of 32 months (range 14-41) and show sustained donor engraftment with 3/5 having full donor chimerism, and 2/5 mixed chimerism (> 85%). We conclude that this regimen is feasible and has low toxicity in Hurler children. In combination with high doses of CD34+ selected cells (> 10 x 10(6)/kg) and donor lymphocyte infusions, stable engraftment could be achieved in unrelated and mismatched related transplantations.

Defibrotide in the treatment of children with veno-occlusive disease (VOD): a retrospective multicentre study demonstrates therapeutic efficacy upon early intervention

Veno-occlusive disease (VOD) of the liver is a complication observed particularly in patients undergoing hematopoietic stem cell transplantation (HSCT). Defibrotide (DF) is a polydeoxyribonucleotide with aptameric activity on endothelium. We evaluated in a retrospective analysis the efficacy of DF in pediatric patients developing hepatic VOD after HSCT.A total of 45 patients between 0.2 and 20 years (median age: 8.2 years) with hepatic VOD were treated with DF: 22 patients (49%) met risk criteria for severe or progressive disease and 23 (51%) for moderately severe and mild disease. The median duration of DF treatment was 17 days. In all, 34 patients (76%) achieved complete response (CR) with a survival rate of 64% at day 100. CR rate in patients with severe disease was 50% with long-term survival of 36%. The average DF dose in the CR group was 45 mg/kg/day and in the no responder (NR) group 27 mg/kg/day. The use of additional drugs besides DF to treat VOD made no difference in the outcome compared to DF alone. The average interval from diagnosis to start of DF was 1 day in the CR and 5.5 days in NR group. In multivariate analysis, early intervention remained the only significant factor for a CR.

Invasive fungal infections are responsible for one-fifth of the infectious deaths in children with ALL

The following report will discuss in detail all lethal invasive fungal infections (IFI) that occurred in a group of 2021 children with acute lymphoblasic leukaemia (ALL). The German ALL-Berlin-Frankfurt-Muenster (BFM) study group is one of the largest cooperation for the treatment of childhood ALL. Between 1995 and 2000, 2021 children with ALL received chemotherapy according to the German BFM 95 protocols (ALL-BFM 95). This population was retrospectively screened, whether a lethal fungal infection occurred: totally, in this group, 43 of 2021 (2.1%) children died because of infections. Nine of 43 (21%) patients died in the context of an IFI: six fatal Aspergillus infections and three fatal yeast infections were reported. The following report will focus on the nine children with ALL who died from IFI. The underlying risk factors (RF) included neutropenia (seven of nine patients) and steroid medication (nine of nine patients). Seven of nine children had additional medical complications (e.g. liver failure, haemolytic uraemic syndrome and acute renal failure). In six of nine children the fungal infection was progressive despite intravenous antimycotic therapy, three patients received no antifungal therapy, as IFI was not considered. The progression of IFI despite antimycotic therapy illustrates the inherent problems of diagnosis and the need for innovative therapeutic modalities. The high percentage (21%) of death from IFI among lethal infections in paediatric ALL patients illustrates the relevance of fungi in this group of patients. On the contrary, the total number of IFI in paediatric ALL patients remains to be determined, as only lethal infections were included in this report.

CD56bright cells differ in their KIR repertoire and cytotoxic features from CD56dim NK cells

In this study we present new differential characteristics of NK cells expressing CD56 surface antigen in low (CD56dim) or high (CD56bright) density. In contrast to CD56bright NK cells CD56dim cells express killer cell immunoglobulin (Ig)-like receptors (KIR) such as CD158a, CD158b, and NKB1. However, c-type lectin-like receptors (KLR) CD94/NKG2 and CD161 are present on both subsets. The ability to form conjugates with susceptible targets is approximately twice as strongly pronounced in CD56dim vs. CD56bright NK cells. Last but not least, granules of CD56dim cells contain about tenfold more perforin and granzyme A enabling potentially more effective cytolysis compared to CD56bright NK cells. On the other hand, CD56bright NK cells are superior in producing the proinflammatory cytokines IFN-gamma (28.5% vs. 20.8%, p<0.05) and TNF-alpha (28% vs. 15.8%, p<0.001). The different NK cell populations retained their specific phenotype in vitro during culture in the presence of IL-2 contradicting that they simply display different stages of maturity. Taken together our data support the view that CD56bright cells are specialized NK cells that regulate immunological response mechanisms rather by cytokine supply than by their cytotoxic potential. The poor cytolytic capacity of CD56bright NK cells can be explained by weak ability in forming conjugates with target cells and low contents of perforin and granzyme A in their granules.

CD56bright cells differ in their KIR repertoire and cytotoxic features from CD56dim NK cells

In this study we present new differential characteristics of NK cells expressing CD56 surface antigen in low (CD56dim) or high (CD56bright) density. In contrast to CD56bright NK cells CD56dim cells express killer cell immunoglobulin (Ig)-like receptors (KIR) such as CD158a, CD158b, and NKB1. However, c-type lectin-like receptors (KLR) CD94/NKG2 and CD161 are present on both subsets. The ability to form conjugates with susceptible targets is approximately twice as strongly pronounced in CD56dim vs. CD56bright NK cells. Last but not least, granules of CD56dim cells contain about tenfold more perforin and granzyme A enabling potentially more effective cytolysis compared to CD56bright NK cells. On the other hand, CD56bright NK cells are superior in producing the proinflammatory cytokines IFN-gamma (28.5% vs. 20.8%, p<0.05) and TNF-alpha (28% vs. 15.8%, p<0.001). The different NK cell populations retained their specific phenotype in vitro during culture in the presence of IL-2 contradicting that they simply display different stages of maturity. Taken together our data support the view that CD56bright cells are specialized NK cells that regulate immunological response mechanisms rather by cytokine supply than by their cytotoxic potential. The poor cytolytic capacity of CD56bright NK cells can be explained by weak ability in forming conjugates with target cells and low contents of perforin and granzyme A in their granules.

CD56bright cells differ in their KIR repertoire and cytotoxic features from CD56dim NK cells

In this study we present new differential characteristics of NK cells expressing CD56 surface antigen in low (CD56dim) or high (CD56bright) density. In contrast to CD56bright NK cells CD56dim cells express killer cell immunoglobulin (Ig)-like receptors (KIR) such as CD158a, CD158b, and NKB1. However, c-type lectin-like receptors (KLR) CD94/NKG2 and CD161 are present on both subsets. The ability to form conjugates with susceptible targets is approximately twice as strongly pronounced in CD56dim vs. CD56bright NK cells. Last but not least, granules of CD56dim cells contain about tenfold more perforin and granzyme A enabling potentially more effective cytolysis compared to CD56bright NK cells. On the other hand, CD56bright NK cells are superior in producing the proinflammatory cytokines IFN-gamma (28.5% vs. 20.8%, p<0.05) and TNF-alpha (28% vs. 15.8%, p<0.001). The different NK cell populations retained their specific phenotype in vitro during culture in the presence of IL-2 contradicting that they simply display different stages of maturity. Taken together our data support the view that CD56bright cells are specialized NK cells that regulate immunological response mechanisms rather by cytokine supply than by their cytotoxic potential. The poor cytolytic capacity of CD56bright NK cells can be explained by weak ability in forming conjugates with target cells and low contents of perforin and granzyme A in their granules.

Variant translocations in sporadic Burkitt's lymphoma detected in fresh tumour material: analysis of three cases

Burkitt's lymphoma/Burkitt cell leukaemia (BL) is characterized by one of the reciprocal translocations involving the MYC oncogene on chromosome 8 and one of the immunoglobulin (Ig) loci on chromosomes 14, 2 or 22. In the few cell lines with the variant translocations t(2;8) and t(8;22) reported to date, the breakpoints on chromosome 8 were located downstream of MYC at a distance of up to 300 kb and more. Here, we describe three new cases with variant translocations. Fresh tumour material from paediatric patients, negative for the common translocation t(8;14), was analysed using a long-distance (LD) polymerase chain reaction (PCR) approach. On chromosome 8, primers were derived from several different regions 3' of MYC, and on chromosomes 2 and 22 from the constant regions of the Ig kappa (Igkappa) and lambda (Iglambda) genes. One translocation t(2;8) and two t(8;22) were detected. In the t(2;8) translocation, the chromosome 8 breakpoint was located 2 kb 3' of the MYC exon 3 and the chromosome 2 breakpoint within an unrearranged Igkappa locus. The breakpoints of the two translocations t(8;22) were detected 16 kb for one and 58 kb for the other downstream of MYC. Sequencing the t(8;22) translocation in one of the cases showed hypermutation of the translocated variable Vlambda4b gene. The presence of hypermutated variable regions in the t(8;22) case suggests germinal centre B cells as the origin of this translocation. The t(2;8) translocation is the first description of a translocation t(2;8) involving an unrearranged Igkappa gene. A mechanism different from V-J recombination and somatic hypermutation has to be proposed for this translocation.

Clinical relevance of genetic risk factors for thrombosis in paediatric oncology patients with central venous catheters

We prospectively evaluated the clinical relevance of genetic risk factors of thrombosis in 137 paediatric patients with solid tumours or leukaemia/lymphoma. The factor V G1691A (FV-L), the prothrombin G20210A (FII-L) and the homozygous MTHFR variant were examined. In addition, protein C, protein S and antithrombin (AT) deficiency were evaluated in patients with ALL or thrombosis. The inter-group incidence of risk factors and thrombotic events was compared. 73 of the 137 patients had ALL and 64 another form of leukaemia, lymphoma or a solid tumour. They were treated according to the established paediatric tumour protocols ALL-BFM, NHL-BFM, COSS, CWS and others. All patients had central venous lines. No patient received heparin or any other anticoagulant. Endpoints of the study were thrombosis, regular completion of chemotherapy or death. Incidence of mutations in the whole group: FV-L (7.3% heterozygous, 0.7% homozygous); FII-L (2.9% heterozygous, no homozygotes); MTHFR (51.8% heterozygous, 10.9% homozygous). Ten patients (7.3%), 6 with ALL and 4 with solid tumours, developed thrombosis. 4 of the 6 patients with ALL and thrombosis (67%) but only 21% of ALL patients without thrombosis had a genetic risk factor (P < 0.013, chi2). No genetic defect was found in the 4 patients with other malignancies and thrombosis. However, besides a tumour, these patients had additional exogenous risk factors including diabetes insipidus and hemiparesis.

CONCLUSION

Genetic mutations appear to be additional risk factors for the development of thrombosis in patients with ALL. In contrast, these mutations do not appear to be relevant risk factors for thrombosis in the small number of children with other malignant diseases reported here. This difference may be due to asparaginase and corticosteroids being used in ALL but not in solid tumour protocols.

Severe protein C deficiency and aseptic osteonecrosis of the hip joint: a case report

Homozygous congenital protein C deficiency is accompanied by severe thrombophilia. Thrombotic events can be reduced in number and severity by lifelong oral anticoagulation therapy. A 4-year-old boy was first diagnosed as having severe congenital homozygous protein C deficiency during the neonatal period when purpura fulminans occurred as the first manifestation of thrombosis. From this time he had been treated with phenprocoumon (INR 3.5-4.5). During an infection of the upper respiratory tract he developed signs of a new episode of purpura fulminans (INR 2.6). Additional anticoagulation therapy with LMW heparin (Clexane) and protein C concentrate was given while the oral anticoagulation therapy was continued. On the third day of this episode the boy suffered from pain of unknown origin. MRI of the abdomen and of the pelvis revealed nontraumatic osteonecrosis of the hip joint. After a few weeks of immobilisation no special treatment was necessary. One year later he was able to walk with no problem.

CONCLUSION

Aseptic osteonecrosis of the hip joint is associated with a variety of disorders including vascular thrombosis and haemorrhage. Especially young children and handicapped patients with thrombophilia and pain of unknown origin are suspected to have thrombosis in atypical regions.

Cerebral venous sinus thrombosis in children with acute lymphoblastic leukemia carrying the MTHFR TT677 genotype and further prothrombotic risk factors

BACKGROUND

The present study was designed to prospectively evaluate the role of prothrombotic risk factors in leukemic children treated according to the ALL-BFM 90/95 study protocols with respect to the onset of cerebral venous sinus thrombosis.

PATIENTS

317 consecutive leukemic children aged 6 months to 18 years were enrolled in this study. 288 of the 317 patients were available for thrombosis-free survival analysis.

RESULTS

In 17 (5.9%) of these 288 patients cerebral venous sinus thrombosis occurred. The overall event-free survival of thrombosis in the central nervous system in patients with at least one prothrombotic defect (n = 12) was significantly reduced compared with patients without a prothrombotic defect (p < 0.0001). 15 patients showed acute clinical symptoms at onset of cerebral venous sinus thrombosis, two were asymptomatic. Three of the 17 patients affected (17.6%) died directly associated with the thrombotic event during induction therapy, the remaining 14 patients did not show prolonged clinical symptoms.

CONCLUSIONS

Prothrombotic risk factors should be included in a screening program in ALL children treated according to the BFM study protocols. Further prospective studies are recommended to establish adequate prophylactic anticoagulant treatment during ALL (BFM) polychemotherapy.

Expression and regulation of c-kit receptor and response to stem cell factor in childhood malignant T-lymphoblastic cells

The cytokine stem cell factor (SCF) synergizes with IL-7 to enhance the proliferation of thymocytes. We therefore investigated the role of the SCF receptor, the protooncogene c-kit, in the pathogenesis of pediatric T-lineage malignancies. Expression and regulation of c-kit in cells from children with non-Hodgkin's lymphoma (T-NHL) or acute lymphoblastic leukemia (T-ALL) and the proliferative effect of SCF on these cells were examined in seven cell lines and 21 biopsy tumor cell preparations. Inducibility of c-kit receptors by SCF, IL-1beta, IL-2, IL-7, TGF-beta, TNF-alpha, PMA or calcium ionophore A23187 was studied by flow cytometry (FCM). C-kit receptors were detected in three out of seven T-lymphoblastic cell lines and in nine out of 21 biopsy tumor cell preparations. Upregulation of c-kit could be induced by cultivation, and to a higher extent by cultivation and addition of IL-1beta, TNF-alpha, TGF-beta or A23187. Downregulation of c-kit occurred in the presence of SCF or PMA. SCF caused a downregulation of c-kit receptors in eight of nine, and a proliferative response in three of 11 c-kit-positive T-lymphoblastic cell preparations. We conclude that c-kit is able to transduce a growth stimulatory signal in some T-lymphoblastic cells and that its expression may not be detectable in a resting metabolic or proliferative state.

[Detection of translocation t(8;14)(q24;132) in pediatric Burkitt's lymphomas using "long distance" polymerase chain reaction: a new method for diagnosis of Burkitt's lymphomas]

The pediatric Non-Hodgkin's lymphomas are a heterogeneous group of malignancies of B- or T-cell origin. Approximately half of them are characterized as Burkitt's lymphomas. Typically, one of the reciprocal translocations t(8;14)(q24;q32), t(2;8)(p11;q24) or t(8;22)(q24;q11) is seen in the tumor cell, each involving the protooncogene c-myc on chromosome 8. Characteristically, in most patients the translocation occurs between the distal end of the long arm on chromosome 8 (c-myc) and chromosome 14 (immunoglobulin heavy chain locus, IgH). The breakpoint regions are distributed over a wide range of more than 10 Kb on chr. 8 and over several hundred Kb on chr. 14. With standard-PCR, fragments can only be amplified to a size of about 2 Kb. The development of PCR-applications to generate long products up to 20 Kb now allows a detection of these breakpoints. Several primer pairs from different regions of the IgH-gene and the c-myc-gene were tested in each patient. Until now, 20 patients with Burkitt's Lymphoma or B-ALL characterized by L3 morphology were examined. All patients were treated according the protocols of the NHL-BFM '90 or '95 study. In 11/20 patients, recombinations between chromosomes 8 and 14 could be detected with our primer pairs. In serial dilutions of DNA from malignant cells in DNA from healthy controls, sensitivities of one malignant cell in 2 x 10(4) normal cells could be obtained. This method will now allow us to characterize the involved breakpoints more exactly and to analyze patient samples (blood, bone marrow, aphereses products and residual tumors) during or after therapy for the existence of minimal residual tumor cells.

Absence of IL-6 receptor expression in fresh childhood Burkitt's lymphoma cells and induction of IL-6 receptors by Epstein-Barr virus in vitro

Interleukin-6 (IL-6) is a cytokine which is necessary for the differentiation of activated B cells and growth of early haemopoietic progenitors. It is used for ex-vivo expansion of myeloid progenitors in the setting of high-dose chemotherapy with autologous bone marrow transplantation (BMT). Expression of the IL-6 receptor (IL-6R) was examined in six fresh Burkitt's lymphoma (BL) cell preparations and 12 BL cell lines by reverse transcriptase polymerase chain reaction (RT-PCR) and flow cytometry (FCM). Inducibility of IL-6R mRNA expression by Epstein-Barr virus (EBV) was studied by comparing two uninfected cell lines with the same cell lines infected by EBV The phenotype of the BL cells lines was analysed by FCM and by proliferation assays in the presence of anti-IgM antibodies. None of the fresh BL cells expressed the IL-6 receptor. The BL cell lines expressed varying degrees of IL-6R mRNA and protein. In vitro infection of EBV-negative BL cell lines resulted in up-regulation of IL-6R mRNA. There was no proliferative response of the BL cell lines to IL-6, including the cells that expressed the receptor. Compared to uninfected BL cell lines, EBV-infected cell lines and lymphoblastoid cell lines (LCLs) showed a weaker or no response to anti-IgM antibodies, indicating a more mature phenotype of these cells. We conclude that the IL-6 receptor is not expressed in fresh childhood BLs, but only in BL cell lines. EBV infection in vitro leads to an up-regulation of IL-6R mRNA but not to increased proliferation. This makes growth stimulation of contaminating BL cells in the setting of autologous BMT unlikely.

Clinical relevance of point mutations in the cytoplasmic domain of the granulocyte colony-stimulating factor receptor gene in patients with severe congenital neutropenia

Recently, point mutations in the gene of the granulocyte colony-stimulating factor (G-CSF) receptor have been reported in two patients with severe congenital neutropenia who developed acute myeloid leukemia (AML). We investigated the frequency of these specific G-CSF receptor mutations in patients with congenital neutropenia undergoing treatment with r-metHuG-CSF (Filgrastim) and the clinical relevance of these mutations. Nucleotides 2306 to 2561 including the critical region (nucleotides 2384-2429) from the intracellular domain of the G-CSF receptor gene were amplified by reverse transcriptase-polymerase chain reaction. Detection of point mutations was performed with specific restriction enzyme analysis, as well as sequencing of PCR products. Both genomic DNA and cDNA from neutrophils and mononuclear cells were analyzed from 28 patients with severe congenital neutropenia. Four of 28 patients with congenital neutropenia displayed a point mutation in the tested cytoplasmic region of the G-CSF receptor gene. The point mutations replace a glutamine codon by a stop codon of the G-CSF receptor gene. Among these four congenital neutropenia patients with a mutated G-CSF receptor, two developed AML. All four patients were investigated regularly and no correlation between occurrence of G-CSF receptor mutation and time or dose of r-metHuG-CSF treatment was found. No point mutations in the G-CSF receptor critical domain could be detected in cells from the other 24 congenital neutropenia patients. Furthermore, we tested six family members of the two patients with AML including mothers and fathers, one sister, and one brother who suffers from congenital neutropenia, as well. All family members displayed a normal G-CSF receptor gene. After the acquisition of the G-CSF receptor mutations, the congenital neutropenia patients continued to respond to G-CSF therapy with an increase in absolute neutrophils in the peripheral blood. We conclude that the point mutations in the critical region of the intracellular part of the G-CSF receptor occur spontaneously and are not inherited. From our data, we suggest that the described G-CSF receptor point mutations do not alter the response to treatment with r-metHuG-CSF and are not the cause of severe congenital neutropenia.

C-kit receptors in childhood malignant lymphoblastic cells

The product of the protooncogene c-kit is the receptor for the hematopoietic cytokine stem cell factor (SCF). C-kit is expressed on leukemic cells of the erythroid, myeloid, and mast-cell lineage and SCF has a proliferative effect on some of these cells. The role of SCF and c-kit in lymphoid malignancies is much less clear. Here we review the role of c-kit in normal lymphopoiesis and summarize its role in lymphoid malignancies. C-kit is expressed in normal lymphopoiesis and its ligand SCF synergizes with IL-7 to enhance the proliferation of B- and T-cell progenitors. In malignant lymphopoiesis, c-kit can also be expressed in B and T-lymphoblastic cells from children with non Hodgkin's lymphoma (NHL) or acute lymphoblastic leukemia (ALL) when analyzed by the highly sensitive reverse transcriptase polymerase chain reaction (RT-PCR). While c-kit receptors were detected by flow cytometric (FCM) analysis on about 40% of fresh T-lymphoblastic biopsy tumor cell preparations or T-lymphoblastic cell lines, no receptors were detected on B-lymphoblastic fresh cells or cell lines from children with B-ALL or Burkitt's lymphoma (BL). Almost all of the lymphoblastic cells expressing c-kit protein responded to recombinant human (rh)SCF with a downregulation of c-kit receptors. A proliferative response was detected only in a minority of these cells. B-ALL or BL cell lines showed no response to rhSCF. Upregulation of c-kit in T-lymphoblastic cells could be demonstrated by the addition of IL-1 beta, TNF-alpha, TGF-beta or A23187, and downregulation by rhSCF or phorbol myristate acetate (PMA). Despite upregulation of c-kit mRNA, protein remained undetectable on B-ALL or BL cells in the presence of A23187. The metabolic state of the cells seemed to influence c-kit expression, since c-kit was upregulated in T-lymphoblastic cells by the addition of new medium. C-kit appears to play a role in the growth of some malignant T-lymphoblastic but not B-lymphoblastic cells.

Application of long PCR to detect t(8;14)(q24;q32) translocations in childhood Burkitt's lymphoma and B-ALL

BACKGROUND

Burkitt's lymphoma (BL) and B-ALL are characterized by chromosomal translocations juxtaposing the c-myc gene on chromosome 8 to one of the immunoglobulin loci. Translocations involving the immunoglobulin heavy chain (IgH) on chromosome 14 are found in approximately 75%-90% of these tumors. The breakpoint regions are located over a wide range on both chromosomes.

PATIENTS AND METHODS

To detect the translocations, we developed a PCR method to generate long products. After extraction of genomic DNA (QiaAmp System, Qiagen, Hilden, Germany), DNA was amplified using a mixture of Taq and Pwo polymerases (Boehringer Mannheim, Germany). Several primer pairs from the S mu, JH, CH1 and the C alpha regions on IgH and from exon 1 and intron 1 of the c-myc gene were tested in each patient.

RESULTS

Lymphoma cells from 20 children with Burkitt's lymphoma and B-ALL characterized by FAB-L3 morphology were examined. In 11/20 patients, recombinations between chromosomes 8 and 14 could be detected with our primer pairs. PCR products from 800 to 3700 bp in length were obtained reproducibly. After amplification, the products were characterized by restriction enzyme digestion, hybridization, and in part by direct sequencing.

CONCLUSIONS

This PCR-based method will allow us (1) to determine the localization of chromosomal breakpoints in primary tumor material, (2) to investigate whether distinct breakpoints are associated with treatment outcome, and (3) to detect the presence of minimal residual tumor cells during or after therapy.

Absence of c-kit receptor and absent proliferative response to stem cell factor in childhood Burkitt's lymphoma cells

The cytokine stem cell factor (SCF) synergizes with interleukin-7 (IL-7) to enhance the proliferation of pre-B cells. To examine the role of SCF and its receptor, c-kit, in the pathogenesis of pediatric Burkitt's lymphomas (BL), we investigated the expression of SCF and c-kit in BL cells and the mitogenic activity of SCF on BL cells. A panel of 13 BL cell lines and 7 fresh biopsy tumors was investigated. BL cells were stimulated either by Epstein-Barr virus (EBV) infection or by different reagents and cytokines, and expression of SCF and c-kit was studied on the mRNA level by Northern blot analysis and reverse-transcriptase polymerase chain reaction (RT-PCR), followed by Southern blotting. c-kit expression was also studied by fluorescence-activated cell sorting and by crosslinking of digoxigenin-labeled recombinant human SCF to the cell surface. Proliferation of BL cell lines was measured by 3H-thymidine incorporation. Low-level expression of c-kit mRNA was detected in 2 of 13 unstimulated BL cell lines and in 1 fresh BL tumor. One cell line showed upregulation of c-kit mRNA with A23187 and downregulation with phorbol myristate acetate. Neither c-kit nor SCF could be detected in any other cell line under any condition of stimulation as analyzed by Northern blot analysis, RT-PCR followed by Southern blot analysis, crosslinking, and immunofluorescence. No response to SCF was seen in 3H-thymidine incorporation assays. We conclude that most BL cells express neither SCF nor c-kit and that the low-level expression of c-kit in some BL cells most likely has no biologic significance.

Absence of G-CSF receptors and absent response to G-CSF in childhood Burkitt's lymphoma and B-ALL cells

The expression of the granulocyte colony-stimulating factor (G-CSF) receptor in childhood Burkitt's lymphoma (BL) cells, and the mitogenic effect of G-CSF on these cells, was studied in a panel of 13 Epstein-Barr virus (EBV) positive and negative BL cell lines derived from nine children. G-CSF receptor mRNA expression was investigated by Northern blot analysis and reverse transcriptase polymerase chain reaction (RT-PCR). Binding of G-CSF to BL cell lines was measured by chemical crosslinking of 125I-G-CSF, and proliferation by thymidine incorporation. Inducibility of the G-CSF receptor was studied by stimulation with interleukin-1 beta, tumour necrosis factor-alpha, Staphylococcus aureus Cowan A, anti-human IgM, phorbol myristate acetate, calcium ionophore A23187, and by infection in vitro by immortalizing and non-immortalizing strains of EBV. BL cell lines, unstimulated or stimulated by biological reagents or EBV infection, did not bind radioionated G-CSF in crosslinking experiments. No stimulation by recombinant human G-CSF was observed in 3H-thymidine incorporation assays. No G-CSF receptor mRNA was detected by Northern blot analysis or RT-PCR in BL cell lines. It is concluded that G-CSF plays no direct stimulatory role in the growth of these malignant B-cells, making a deleterious influence of G-CSF in the clinical treatment situation unlikely.

Non-Hodgkin's lymphomas of childhood and adolescence: results of a treatment stratified for biologic subtypes and stage--a report of the Berlin-Frankfurt-Münster Group

PURPOSE

To prove the efficacy of a treatment stratified according to histology for children with non-Hodgkin's lymphoma (NHL), including acute B-cell leukemia (B-ALL).

PATIENTS AND METHODS

From October 1986 to March 1990, 302 assessable patients, 0.6 to 17.8 years of age, with newly diagnosed NHL were enrolled onto study ALL/NHL-BFM 86. Fifty percent of patients had Burkitt-type lymphomas, including B-ALL; 24% had lymphoblastic lymphoma; 18% had diffuse large-cell lymphoma; and 8% had an NHL not further classified. Therapy group B included Burkitt's-type lymphomas, B-ALL, and most large-cell lymphomas including Ki-1 anaplastic large-cell lymphoma. Patients with stage I and II disease resected received three, while all others received six, 5-day therapy courses (dexamethasone, methotrexate [MTX] 0.5 g/m2 [5 g/m2 for stage IV and B-ALL], and intrathecal [IT] therapy in each course, plus ifosfamide, cytarabine, and etoposide alternating with cyclophosphamide and doxorubicin). Therapy for group non-B patients (lymphoblastic lymphoma and pleomorphic T-cell lymphoma [PTCL]) consisted of a Berlin-Frankfurt-Münster (BFM) acute lymphoblastic leukemia protocol, including cranial irradiation for advanced stage. Local therapy was restricted to patients with incomplete tumor regression.

RESULTS

The probabilities of event-free survival (pEFS) at 7 years were 80% +/- 2% for the whole group, 81% +/- 3% for group B (n = 225), and 78% +/- 5% for group non-B (n = 77) with a follow-up duration of 3.6 to 7 years (median 5 years). Treatment results were comparable between NHL subtypes, except for PTCL, in which three of four patients suffered from relapse. Local disease manifestations were the most frequent site of failure.

CONCLUSION

This therapy strategy provided patients of all NHL subtypes with an equally high chance to survive event-free, except patients with PTCL. With reduced systemic failure, local tumor control may become more important.

[NHL-BFM 90 therapy study in treatment of malignant non-Hodgkin's lymphomas in children and adolescents. Part 1: Classification and allocation to strategic therapy groups. BIF study group]

One of the goals of the study NHL-BFM 90 was to investigate the distribution and prognosis of the different subtypes of Non-Hodgkin's Lymphoma (NHL) in children and adolescents according to histological, cytomorphological and immunological characteristics. From 4/1990 to 12/1992, 346 patients (pts) (84 females, 262 males) were enrolled (median age: 9.1 years; range: 0.8-17.9 years). Histology was available from 290 pts (84%), cytomorphology from 155 (44%), and immunophenotyping from 245 (70%). Cases with L1 oder L2 cytomorphology according to the French-American-British Classification were classified as lymphoblastic lymphoma and those with L3 cytomorphology as Burkitt-Type lymphoma or acute B-cell leukemia (B-ALL) if a histological classification was not available. By means of the combined analysis of all three diagnostic criterias the classification of the NHL according to the updated Kiel-classification was possible in 312 cases: 49% were classified as Burkitt-type-lymphoma (incl. B-ALL), 22% als lymphoblastic lymphoma, 10% as large cell anaplastic lymphoma (LCAL), 6% as centroblastic lymphoma, only few cases were classified as NHL of other subtypes, 3 pts (1%) suffered from low grade malignant lymphomas, and in 34 pts (10%) the NHL was not further classified. Patients were stratified according to NHL-subentities in 3 branches (Non-B-NHL, B-NHL, LCAL) of different treatment modalities. The estimated probability of a 3-year event free survival (pEFS) was 88 +/- 2% for the whole group (follow up 7 to 40 months, median 23 months) while pEFS of different subtypes was: lymphoblastic lymphoma: 91 +/- 4%; Burkitt-type-lymphoma/B-ALL: 90 +/- 2%; centroblastic lymphoma: 94 +/- 6%, LCAL: 88 +/- 6%. We conclude that the stratification of treatment modalities in study NHL-BFM 90 according to biological entities provided patients of different NHL-subtypes an equal chance to survive event free. The efficacy of the treatment strategy for rare subtypes, however, is not evaluable yet.

Differential regulation of stem cell factor mRNA expression in human endothelial cells by bacterial pathogens: an in vitro model of inflammation

Production of hematopoietic growth factors by endothelial cells plays a pivotal role during inflammatory processes. Stem cell factor (SCF) is known to be expressed constitutively in endothelial cells. To investigate the regulation of this cytokine expression by inflammatory stimuli, we cocultured human umbilical vein endothelial cells (HUVEC) with various gram-negative bacterial strains (Escherichia coli, Yersinia enterocolitica, Chlamydia trachomatis, and Neisseria meningitidis, respectively). Experiments were performed with bacterial concentrations ranging from 10(2) to 10(7) bacteria/mL for 3 hours. SCF-specific mRNA expression was studied using Northern blot analysis. Stimulation with the enteropathogenic bacterial strains Y enterocolitica and E coli resulted in a significant concentration-dependent increase of SCF mRNA expression. Similar results were obtained in coculture experiments with N meningitidis. As shown in experiments with E coli, the accumulation of SCF transcripts was also time-dependent. In contrast, coculture of HUVEC with the intracellular gram-negative strain C trachomatis had no effect on SCF mRNA expression. To elucidate the role of the gram-negative bacterial cell wall components, we stimulated HUVEC with bacterial lipopolysaccharide (LPS). LPS induced a maximal SCF mRNA accumulation within 2 hours followed by decrease of SCF-specific transcripts to the basal level after 24 hours. In addition, we exposed HUVEC to the classical inflammatory cytokine interleukin-1 alpha (IL-1 alpha). Kinetic experiments showed a similar pattern of regulation with an increase of SCF mRNA within 2 hours, persisting up to 12 hours, and a decrease to basal transcription after 24 hours. From these data, we conclude that SCF expression is regulated by inflammatory stimuli, such as IL-1 alpha and bacterial pathogens, suggesting an important role of SCF during inflammation.

Type II congenital dyserythropoietic anemia in a patient with ectodermal dysplasia. Distinction from dyskeratosis congenita

PURPOSE

We describe a patient who presented with severe anemia and ectodermal dysplasia.

PATIENTS AND METHODS

This is a case report of a patient whose anemia was evaluated at New York Hospital and then returned to Australia where further testing was performed.

RESULTS

The history indicated that this was a chronic anemia. Bone marrow examination showed binucleated late normoblasts consistent with congenital dyserythropoietic anemia type II (CDA II) and not dyskeratosis congenita. Paroxysmal nocturnal hemoglobinuria was excluded despite the presence of a positive sucrose hemolysis test. Other types of acquired and congenital anemias were excluded by testing.

CONCLUSIONS

This is the first patient reported with coincident CDA II and ectodermal dysplasia.

T-cell activation defect in common variable immunodeficiency: restoration by phorbol myristate acetate (PMA) or allogeneic macrophages

Common variable immunodeficiency (CVI) represents a group of familial and sporadic diseases characterized by a range of B-cell, T-cell, and macrophage defects. A defect in T-cell activation, involving reduced proliferation and IL-2 production after stimulation with OKT3 antibody, has been described previously. In the present study we found that these defects could be corrected in vitro by adding phorbol myristate acetate (PMA) to OKT3-stimulated peripheral blood mononuclear cells (PBMC) of 14 patients with CVI. PBMC of 6 out of 7 patients with CVI studied also exhibited a profound defect in IL-2 receptor expression when incubated with OKT3 antibody. IL-2 receptor expression after stimulation with PMA alone was normal, indicating that the OKT3- but not the PMA-induced pathway of IL-2 receptor expression was defective. On the RNA level, the genes for IL-2 and IL-2 receptor were expressed after stimulation with OKT3 antibody. IL-2 and IL-2 receptor gene expression were normal, indicating a possible post-transcriptional defect. To investigate whether the defect in T-cell activation was at the macrophage or the T-cell level, we prepared adherent cells and monocyte-depleted T cells (E+) from 3 patients with CVI and from normal blood donors. Incubating CVI E+ cells with normal adherent cells resulted in normal proliferation and IL-2 production in the presence of OKT3, whereas incubation of normal E+ cells with adherent cells from patients with CVI under the same conditions showed reduced IL-2 production and proliferation, suggesting the macrophage as the origin of the failure in T-cell activation in the patients with CVI studied. Inhibition by macrophage-secreted prostaglandins was excluded by failure to correct the IL-2 production and proliferation defects in the presence of indomethacin.

Human interleukin 2 gene is located on chromosome 4

The interleukin-2 (IL2) gene is assigned to human chromosome 4. A synthetic oligonucleotide representing bases 285 to 324 of the IL2 cDNA clone described by Taniguchi et al. [Nature (London) 302:305-310, 1983] was used as hybridization probe in Southern blots. Eco RI digests of DNA derived from 11 somatic mouse-human cell hybrid clones were used. The IL2 gene was localized to human chromosome 4 based on the observed combinations of segregating chromosomes and bands. Under the conditions of stringency utilized, a single 3.6 kilobase Eco RI fragment hybridized to the oligonucleotide. Molecular weight standards were provided by rehybridizing the blots with an actin cDNA clone, pAct 1, which identified actin gene Eco RI fragments of defined size.

Properties of the avian viral protein p12

The avian RNA tumour virus structural protein p12 was purified from avian myeloblastosis virus (AMV) by nucleic acid affinity chromatography to apparent homogeneity as judged from SDS--polyacrylamide gel electrophoresis. A filter binding assay was used for the identification of p12. High concentrations of p12 precipitated nucleic acids out of solution in the absence of MgCl2. Binding of p12 to single-stranded nucleic acids protected them from digestion with nucleases and resulted in a hyperchromic effect. These phenomena were reversible in the presence of salt. The affinity of p12 to nucleic acids was determined by competing for the binding of p12 to denatured radioactive DNA by various other nuclei acids. It was found that p12 bound preferentially to single-stranded nucleic acids and showed a higher affinity to poly(rI) than to poly(rC) and poly(rA). Purified RNA-dependent DNA polymerase activity from AMV was stimulated up to sixfold by p12, depending on the template. Solubilization of RNA in RNA--DNA hybrids by RNase H was inhibited in the presence of p12.

The isolation of avian viral RNA and polypeptides

From the same batch of virus, the four major avian viral structural proteins p27, p19, p15, and p12, the reverse transcriptase, the envelope glycoprotein gp85, and the high molecular weight 70 S RNA have been recovered. All proteins, except for gp85, have been purified by use of column chromatography procedures to apparent homogeneity as judged by sodium dodecyl sulfate-polyacrylamide gels and isoelectric focusing. A new isolation procedure for p12 by affinity column chromatography takes advantage of its nucleic acid binding properties. The recovery of nondenatured viral structural proteins is demonstrated by the proteolytic activity revealed by p15. The purified proteins were used for the production of monospecific antibodies. The 70 S RNA served as source for the isolation of 35 S RNA subunits.