Collaborative multicenter investigation of marrow transplantation for sickle cell disease: current results and future directions

We present updated results of a multicenter collaborative investigation of bone marrow transplantation for sickle cell disease. Between September 1991 and April 1997, thirty-four children less than 16 years of age with severe sickle cell disease received marrow allografts from HLA-identical siblings. Indications for transplantation included a history of stroke (n = 17), recurrent acute chest syndrome or sickle pulmonary disease (n = 10), and recurrent vaso-occlusive crises (n = 7). Twenty-one patients received regular red blood cell (RBC) transfusions to prevent complications of sickle cell disease. Patients were prepared for transplantation with busulfan, cyclophosphamide, and antithymocyte globulin or CAMPATH (Cambridge Pathology) antibody. Thirty-two of the 34 patients survived, with a median follow-up of 26.5 months (range, 0.2-66.9 months); and 28 patients demonstrated stable engraftment of donor hematopoietic cells. Graft rejection or recurrence of sickle cell disease occurred in four patients, and two patients died of intracranial hemorrhage or graft-vs.-host disease. In the group of 34 children with symptoms of advanced sickle cell disease, current Kaplan-Meier estimates of survival and event-free survival are 93% and 79%, respectively.

Bone marrow transplantation for sickle cell disease

BACKGROUND

We investigated the risks and benefits of allogeneic bone marrow transplantation in children with complications of sickle cell disease.

METHODS

Twenty-two children less than 16 years of age who had symptomatic sickle cell disease received marrow allografts from HLA-identical siblings between September 1991 and April 1995. The indications for transplantation included a history of stroke (n = 12), recurrent acute chest syndrome (n = 5), and recurrent painful crises (n = 5). Patients were prepared for transplantation with busulfan, cyclophosphamide, and antithymocyte globulin.

RESULTS

Twenty of the 22 patients survived, with a median follow-up of 23.9 months (range, 10.1 to 51.0), and 16 patients had stable engraftment of donor hematopoietic cells. In three patients the graft was rejected and sickle cell disease recurred; in a fourth patient graft rejection was accompanied by marrow aplasia. In 1 of the 16 patients with engraftment, there was stable mixed chimerism. Two patients died of central nervous system hemorrhage or graft-versus-host disease. Kaplan-Meier estimates of survival and event-free survival at four years were 91 percent and 73 percent, respectively. Among patients with a history of acute chest syndrome, lung function stabilized; among patients with prior central nervous system vasculopathy who had engraftment, stabilization of cerebrovascular disease was documented by magnetic resonance imaging.

CONCLUSIONS

Allogeneic stem-cell transplantation can be curative in young patients with symptomatic sickle cell disease.

Interpretation of the complete blood count

The authors' impression is that the CBC provides much more information than is routinely used. When anemia is present, the CBC contains considerable information regarding its cause, which can assist in formulating a differential diagnosis and directing further evaluation. White blood cell and platelet count levels may similarly direct practitioners to consider or dismiss underlying conditions. This article assists the pediatrician in optimizing use of this familiar diagnostic tool.

Barriers to bone marrow transplantation for sickle cell anemia

While allogeneic marrow transplantation is curative therapy for patients with sickle cell anemia, only a small fraction of patients in the United States receive this treatment. We surveyed participants in our multicenter study of marrow transplantation for sickle cell anemia to determine reasons for not proceeding to transplantation. Among the 4848 patients less than 16 years of age with sickle cell anemia that were followed in 22 collaborating centers, 315 (6.5%) patients were reported to meet protocol entry criteria for transplantation, although there was wide variation among the institutions (0.9-36%). Among the 315 patients eligible for transplantation, 128 (41%) had human leukocyte antigen (HLA) typing performed, and of these 44 (14% of those meeting entry criteria) had an HLA-identical sibling. Common reasons for not proceeding with HLA typing in the remaining 187 patients included lack of a candidate sibling donor (76 patients, 24% of those meeting criteria) and lack of financial or psychosocial support (33, 10.5%). Parental refusal (30, 9.5%), physician refusal (13, 4%), history of medical noncompliance (2, < 1%), and other reasons (33, 10.5%) were less frequently cited. To date, 25 patients have been transplanted. Of the remaining 19 patients with HLA-matched donors, seven did not proceed to transplantation because of parental refusal, while the others anticipate a future transplantation (6), have experienced symptomatic improvement (4), or have relocated abroad (2). We conclude that the major barrier to marrow transplantation for sickle cell anemia is lack of an HLA-identical donor. But since only 6.5% of all children with sickle cell disease were considered eligible for transplantation, it is possible that other significant obstacles remain to be identified. For patients reported to meet eligibility criteria, parental refusal and limited financial or psychosocial support were infrequent barriers to transplantation.

Transcriptional enhancers act in cis to suppress position-effect variegation

We have examined the basis of enhancer effects on gene expression by altering the action of enhancers on expression of a stably integrated reporter gene. We used two distinct experimental approaches: recombinase-mediated deletion of an enhancer and modulation of the activity of another enhancer composed of downstream metal response elements (MREs). The flp recombinase was used to delete the 5'HS2 globin enhancer from a site downstream of beta-geo at nine separate integration sites in K562 erythroleukemia cells. In no case does deletion of 5'HS2 have a significant effect on the level of expression; however, the deletion does increase dramatically the rate at which expression of beta-geo is silenced. Zinc stimulation of a metallothionein enhancer has no effect on the level of reporter expression, but slows the rate of silencing. Silencing in both cases is highly site dependent, and resembles position-effect variegation (PEV). These results strongly support a binary mode of enhancer action, as in both cases the enhancer maintains reporter expression without a strong effect on the level of expression. Taken together, these findings suggest that transcriptional activators have a direct interaction with repressive chromatin structures, which is independent of an effect on the rate of transcription. We propose that cis-acting transcriptional control elements may act primarily through this mechanism.

Enhancers increase the probability but not the level of gene expression

We have studied enhancer function in transient and stable expression assays in mammalian cells by using systems that distinguish expressing from nonexpressing cells. When expression is studied in this way, enhancers are found to increase the probability of a construct being active but not the level of expression per template. In stably integrated constructs, large differences in expression level are observed but these are not related to the presence of an enhancer. Together with earlier studies, these results suggest that enhancers act to affect a binary (on/off) switch in transcriptional activity. Although this idea challenges the widely accepted model of enhancer activity, it is consistent with much, if not all, experimental evidence on this subject. We hypothesize that enhancers act to increase the probability of forming a stably active template. When randomly integrated into the genome, enhancers may affect a metastable state of repression/activity, permitting expression in regions that would not permit activity of an isolated promoter.

The role of a substance abuse consultation team in a trauma center

OBJECTIVE

Trauma is a leading cause of morbidity and mortality in the U.S., and substance abuse makes an enormous contribution to this problem as well as to the increased cost of health care. A substance abuse consultation (SAC) team was developed to evaluate and intervene with trauma victims who are suspected of having problems with alcohol and/or other drugs. This study was undertaken to determine the effectiveness of this service.

METHOD

This study is a retrospective review of 100 consecutive trauma admissions who were felt to be at high risk for substance abuse and were referred to the SAC team for evaluation and intervention. This study was undertaken in a tertiary care teaching hospital in a cooperative effort between the trauma center and the addictions program.

RESULTS

All 100 patients were diagnosed with psychoactive substance use disorders and 78 were referred for alcohol and other drug rehabilitation. Of these patients, 62% accepted a referral for drug and alcohol treatment.

CONCLUSIONS

From these preliminary data, it appears that a SAC team may be effective in intervening with hospitalized trauma patients who have alcohol and other drug problems.

Neurologic complications after allogeneic marrow transplantation for sickle cell anemia

Seven of 21 patients with sickle cell anemia developed neurologic complications 5 to 243 days (median, 33 days) after allogeneic marrow transplantation. Among these 7 patients, indications for transplantation included either a past history of stroke (4 patients) or recurrent severe vaso-occlusive events (3 patients). All received marrow from an HLA-identical sibling after preparation with busulfan and cyclophosphamide, and in 4 patients with antithymocyte globulin. Five of 6 patients developing seizures received anticonvulsant and supportive treatment with resolution of neurologic abnormalities. Three patients experienced intracranial bleeding, which was fatal in two. Of the 14 patients free of neurologic complications, 4 patients had experienced stroke before transplantation. However, among all patients with prior stroke, the incidence of intracranial hemorrhage was 38% (3/8), whereas none of the 13 patients without prior stroke developed posttransplant intracranial bleeding (P = .026). We conclude that patients with sickle cell anemia are at increased risk for neurologic complications after marrow ablative therapy and that patients with prior stroke are at increased risk for intracranial hemorrhage. Transplantation of patients before the onset of overt stroke may reduce this risk.

Bone marrow transplantation for thalassemia. The USA experience

PURPOSE

We have reviewed the results of bone marrow transplantation in 30 patients with thalassemia major who were treated in the United States.

PATIENTS AND METHODS

Ten patients who underwent transplantation in Seattle and 20 patients from five other U.S. centers were identified through a survey of the International Bone Marrow Transplant Registry. These transplants were performed between November 1981 and April 1992 in patients with diverse ethnic backgrounds and ranged in age from 6 months to 14 years (median 4.0 years). Twenty-seven of the 30 patients received marrow from a human leukocyte antigen (HLA)-identical sibling or other family member, one patient received HLA-matched marrow from an unrelated donor, and two patients were given haploidentical but HLA-mismatched marrow from a related donor. Cytoreductive (preparative) therapy varied among institutions and pretransplant risk categories. In general, patients were given busulfan (12-24 mg/kg) or dimethylmyleran (5 mg/kg) in combination with cyclophosphamide (120-240 mg/kg). A subset of patients were given total body irradiation (TBI) at a dose of 720 cGy followed by cyclophosphamide (120 mg/kg).

RESULTS

Sixteen of 27 patients (59%) who received marrow from an HLA-identical family member are event-free survivors, with a duration of follow-up ranging from 2 months to > 10 years after transplantation. Six of these 27 patients (22%) had recurrence of thalassemia and five (19%) died. The estimated actuarial rate of thalassemia recurrence was 24% and the rate of event-free survival was 57%. Only one of the three patients who received marrow from HLA-nonidentical or unrelated donors survives event-free. Liver biopsies were not routinely performed before transplant. Thus, classification of patients into Lucarelli risk groups was not possible. A modified risk classification was devised by using liver size and iron status assessed by the regularity of chelation and the serum ferritin level. With use of this classification, there was no significant difference in event-free survival between transplant risk groups.

CONCLUSIONS

The findings observed in this small series of patients confirms that thalassemia can be cured with bone marrow transplantation. Although most patients are event-free survivors, a significant number experienced recurrence of their disease. A cooperative multicenter trial of U.S. transplant centers may be necessary to evaluate the use of marrow transplantation for thalassemia and to determine optimal treatment.

Characterization of polymorphs of a new anti-inflammatory drug

The present study demonstrates the utility of a diversified analytical approach for the characterization and quantitative analysis for two polymorphs of a new anti-inflammatory agent, (+/-)-7-[3-(4-acetyl-3-methoxy-2-propylphenoxy)propoxy-3,4-dihydro -8-propyl- 2H-1-benzopyran-2-carboxylic acid (SC-41930). The existence of two distinct crystal polymorphs of SC-41930 was qualitatively indicated through microscopy and application of thermal methods of analysis. The application of TGA was important for establishing that the two solid forms were, in fact, polymorphs, as opposed to solvated and unsolvated drug substances. The application of IR spectrometry revealed spectral features in the carbonyl stretching region, which were characteristic and unique to the two SC-41930 polymorphs. DRIFT spectrometry was implemented as the sampling method of choice to eliminate the possibility of polymorphic transformations during conventional mulling or KBr pellet sampling procedures. The DRIFT spectrometry procedure permitted development of a quantitative assay for detection of the low-melting polymorph (as an impurity) in high-melting samples. Calibration plots showed acceptable linearity of response from 0 to 25% (w/w) low-melting samples spiked into the high-melting polymorph. The performance characteristics of the method indicated good run-to-run and day-to-day consistency for its intended use.

The Introduction of Bdellodes Lapidaria (Acari: Bdellidae) From Australia Into South Africa for the Biological Control of Sminthurus Viridis (Collembola)

The lucerne flea, S, viridis, was introduced into South Africa with subterranean clover seed imported from Western Australia in 1939. By 1959 the infestation had spread over 50,000 ha and methods of control were examined. The predatory mite B. lapidaria was known to be an effective biological control agent against S. viridis in Australian pastures. From 1963 to 1966 over 75,000 mites were collected in Western Australia and sent by air for immediate release in selected sites in South Africa (Cape Province). The mites were shown to be established in 1965 and multiplied rapidly, enabling redistribution to additional sites. The influence of this predator on S. viridis numbers is now being monitored. Preliminary data indicate that B. lapidaria is capable of influencing flea densities under South African conditions. A definite relationship between the predator and sminthurid Collembola such as S. viridis slnd Bourletiella arvalis is indicated, although B. lapidaria appears to be able to utilize other foods during periods of sminthurid scarcity.