Soluble and membrane-bound interleukin (IL)-15 Rα/IL-15 complexes mediate proliferation of high-avidity central memory CD8+ T cells for adoptive immunotherapy of cancer and infections

The lack of persistence of infused T cells is a principal limitation of adoptive immunotherapy in man. Interleukin (IL)-15 can sustain memory T cell expansion when presented in complex with IL-15Rα (15Rα/15). We developed a novel in-vitro system for generation of stable 15Rα/15 complexes. Immunologically quantifiable amounts of IL-15 were obtained when both IL-15Rα and IL-15 genes were co-transduced in NIH 3T3 fibroblast-based artificial antigen-presenting cells expressing human leucocyte antigen (HLA) A:0201, β₂ microglobulin, CD80, CD58 and CD54 [A2-artificial antigen presenting cell (AAPC)] and a murine pro-B cell line (Baf-3) (A2-AAPC^15Rα/15 and Baf-3^15Rα/15 ). Transduction of cells with IL-15 alone resulted in only transient expression of IL-15, with minimal amounts of immunologically detectable IL-15. In comparison, cells transduced with IL-15Rα alone (A2-AAPC^Rα ) demonstrated stable expression of IL-15Rα; however, when loaded with soluble IL-15 (sIL-15), these cells sequestered 15Rα/15 intracellularly and also demonstrated minimal amounts of IL-15. Human T cells stimulated in vitro against a viral antigen (CMVpp65) in the presence of 15Rα/15 generated superior yields of high-avidity CMVpp65 epitope-specific T cells [cytomegalovirus-cytotoxic T lymphocytes (CMV-CTLs)] responding to ≤ 10^{- 13} M peptide concentrations, and lysing targets cells at lower effector : target ratios (1 : 10 and 1 : 100), where sIL-15, sIL-2 or sIL-7 CMV-CTLs demonstrated minimal or no activity. Both soluble and surface presented 15Rα/15, but not sIL-15, sustained in-vitro expansion of CD62L⁺ and CCR7⁺ central memory phenotype CMV-CTLs (T_CM ). 15Rα/15 complexes represent a potent adjuvant for augmenting the efficacy of adoptive immunotherapy. Such cell-bound or soluble 15Rα/15 complexes could be developed for use in combination immunotherapy approaches.

Late effects in patients with Fanconi anemia following allogeneic hematopoietic stem cell transplantation from alternative donors

Hematopoietic stem cell transplantation (HSCT) is curative for hematological manifestations of Fanconi anemia (FA). We performed a retrospective analysis of 22 patients with FA and aplastic anemia, myelodysplastic syndrome or acute myelogenous leukemia who underwent a HSCT at Memorial Sloan Kettering Cancer Center and survived at least 1 year post HSCT. Patients underwent either a TBI- (N=18) or busulfan- (N=4) based cytoreduction followed by T-cell-depleted transplants from alternative donors. Twenty patients were alive at time of the study with a 5- and 10-year overall survival of 100 and 84% and no evidence of chronic GvHD. Among the 18 patients receiving a TBI-based regimen, 11 (61%) had persistent hemochromatosis, 4 (22%) developed hypothyroidism, 7 (39%) had insulin resistance and 5 (27%) developed hypertriglyceridemia after transplant. Eleven of 16 evaluable patients (68%), receiving TBI, developed gonadal dysfunction. Two patients who received a TBI-based regimen died of squamous cell carcinoma. One patient developed hemochromatosis, hypothyroidism and gonadal dysfunction after busulfan-based cytoreduction. TBI appears to be a risk factor for malignant and endocrine late effects in the FA host. Multidisciplinary follow-up of patients with FA (including cancer screening) is essential for early detection and management of late complications, and improving long-term outcomes.

T-cell depleted allogeneic hematopoietic cell transplants as a platform for adoptive therapy with leukemia selective or virus-specific T-cells

Allogeneic hematopoietic cell transplants adequately depleted of T-cells can reduce or prevent acute and chronic GVHD in both HLA-matched and haplotype-disparate hosts, without post-transplant prophylaxis with immunosuppressive drugs. Recent trials indicate that high doses of CD34+ progenitors from G-CSF mobilized peripheral blood leukocytes isolated and T-cell depleted by immunoadsorption to paramagnetic beads, when administered after myeloablative conditioning with TBI and chemotherapy or chemotherapy alone can secure consistent engraftment and abrogate GVHD in patients with acute leukemia without incurring an increased risk of a recurrent leukemia. Early clinical trials also indicate that high doses of in vitro generated leukemia-reactive donor T-cells can be adoptively transferred and can induce remissions of leukemia relapse without GVHD. Similarly, virus-specific T-cells generated from the transplant donor or an HLA partially matched third party, have induced remissions of Rituxan-refractory EBV lymphomas and can clear CMV disease or viremia persisting despite antiviral therapy in a high proportion of cases. Analyses of treatment responses and failures illustrate both the advantages and limitations of donor or banked, third party-derived T-cells, but underscore the potential of adoptive T-cell therapy in the absence of ongoing immunosuppression.

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.

Graft-versus-host disease after double-unit cord blood transplantation has unique features and an association with engrafting unit-to-recipient HLA match

Manifestations of and risk factors for graft-versus-host disease (GVHD) after double-unit cord blood transplantation (DCBT) are not firmly established. We evaluated 115 DCBT recipients (median age, 37 years) who underwent transplantation for hematologic malignancies with myeloablative or nonmyeloablative conditioning and calcineurin inhibitor/mycophenolate mofetil immunosuppression. Incidence of day 180 grades II to IV and III to IV acute GVHD (aGVHD) were 53% (95% confidence interval, 44 to 62) and 23% (95% confidence interval, 15 to 31), respectively, with a median onset of 40 days (range, 14 to 169). Eighty percent of patients with grades II to IV aGVHD had gut involvement, and 79% and 85% had day 28 treatment responses to systemic corticosteroids or budesonide, respectively. Of 89 engrafted patients cancer-free at day 100, 54% subsequently had active GVHD, with 79% of those affected having persistent or recurrent aGVHD or overlap syndrome. Late GVHD in the form of classic chronic GVHD was uncommon. Notably, grades III to IV aGVHD incidence was lower if the engrafting unit human leukocyte antigen (HLA)-A, -B, -DRB1 allele match was >4/6 to the recipient (hazard ratio, 0.385; P = .031), whereas engrafting unit infused nucleated cell dose and unit-to-unit HLA match were not significant. GVHD after DCBT was common in our study, predominantly affected the gut, and had a high therapy response, and late GVHD frequently had acute features. Our findings support the consideration of HLA- A,-B,-DRB1 allele donor-recipient (but not unit-unit) HLA match in unit selection, a practice change in the field. Moreover, new prophylaxis strategies that target the gastrointestinal tract are needed.

Second-line age-adjusted International Prognostic Index in patients with advanced non-Hodgkin lymphoma after T-cell depleted allogeneic hematopoietic SCT

T-cell depleted allogeneic hematopoietic SCT (TCD-HSCT) have shown durable disease-free survival with a low risk of GVHD in patients with AML. We investigated this approach in 61 patients with primary refractory or relapsed non-Hodgkin lymphoma (NHL), who underwent TCD-HSCT from January 1992 through September 2004. Patients received myeloablative cytoreduction consisting of hyperfractionated total body irradiation, followed by either thiotepa and cyclophosphamide (45 patients) or thiotepa and fludarabine (16 patients). We determined the second-line age-adjusted International Prognostic Index score (sAAIPI) before transplant transplant. Median follow-up of surviving patients is 6 years. The 10-year OS and EFS were 50% and 43%, respectively. The relapse rate at 10 years was 21% in patients with chemosensitive disease and 52% in those with resistant disease at time of HSCT. Nine of the 18 patients who relapsed entered a subsequent CR. OS (P=0.01) correlated with the sAAIPI. The incidence of grades II-IV acute GVHD was 18%. We conclude that allogeneic TCD-HSCT can induce high rates of OS and EFS in advanced NHL with a low incidence of GVHD. Furthermore, the sAAIPI can predict outcomes and may be used to select the most appropriate patients for this type of transplant.

Long-term follow-up of patients treated with daclizumab for steroid-refractory acute graft-vs-host disease

Daclizumab has been shown to have activity in acute GVHD, but appears to be associated with an increased risk of infection. To investigate further the long-term effects of daclizumab, we performed a retrospective review of 57 patients who underwent an allogeneic hematopoietic stem cell transplant from January 1993 through June 2000 and were treated with daclizumab for steroid-refractory acute GVHD. The median number of daclizumab doses given was 5 (range 1-22). GVHD was assessed at baseline, days 15, 29 and 43. By day 43, 54% patients had an improvement in their overall GVHD score, including 76% patients aged < or =18. Opportunistic infections developed in 95% patients. Forty-three patients (75%) died following treatment with daclizumab. The causes of death included active GVHD and infection (79%), active GVHD (5%), chronic GVHD (2%) and relapse (14%). Patients with grade 3-4 GVHD had a significantly shorter median survival than patients with grade 1-2 GVHD (2.0 vs 5.1 months, P=0.001). Daclizumab has no infusion-related toxicity, is active in steroid-refractory GVHD, especially among pediatric patients, but is associated with significant morbidity and mortality due to infectious complications. Careful patient selection and aggressive prophylaxis against viral and fungal infections are recommended.

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.

Predictors for persistent cytomegalovirus reactivation after T-cell-depleted allogeneic hematopoietic stem cell transplantation

Cytomegalovirus (CMV) reactivation occurs in up to 60% of CMV-seropositive recipients after allogeneic hematopoietic stem cell transplantation (HSCT). The incidence of CMV disease among T-cell-depleted HSCT patients has been reported from 5-15%. The incidence of reactivation refractory to antivirals in this population is not well studied.

METHODS

In this retrospective study we characterized the outcome of CMV reactivation in a cohort of 255 adult and pediatric patients who underwent T-cell-depleted HSCT at Memorial Sloan-Kettering Cancer Center from September 1999 through August 2004. CMV infection was monitored by the pp65 antigenemia assay (CMV Ag). Persistent reactivation was defined as antigenemia positivity >21 days on antiviral therapy.

RESULTS

Of 118 CMV-seropositive recipients, 69 (58.4%) had reactivated CMV. Twenty of 69 (29%) developed persistent reactivation at first episode of reactivation, and 7 (10%) in subsequent episode. All patients with persistent reactivation received >/=2 antivirals and CMV hyperimmune globulin; 45% received combination antiviral therapy. The median duration of persistent reactivation was 98 days, range 31-256 days. In multivariate analysis, maximum CMV Ag >25 cells/slide was associated with persistent reactivation (odds ratio 16.2%, 95% confidence interval 4-64, P<0.0001). CMV disease occurred in 6/27 (22%) patients with persistent reactivation. Patients with persistent reactivation had lower CD4(+) and CD8(+) lymphocyte counts compared with those with non-persistent reactivation at day +90 post HSCT (P=0.01 and 0.02, respectively).

CONCLUSIONS

Persistent reactivation occurred in 39% of T-cell-depleted HSCT despite treatment with currently available antivirals. Maximum CMV Ag >25 cells/slide was associated with persistent CMV reactivation. More effective treatment modalities are needed for this high-risk population to reduce CMV-associated morbidity and mortality.

Final height in pediatric patients after hyperfractionated total body irradiation and stem cell transplantation

Impaired linear growth has been shown to occur in individuals treated during childhood with single-dose and fractionated total body irradiation (TBI) before stem cell transplantation. Our objective was to describe the final heights attained and patient/treatment factors correlating with final height in a cohort of childhood cancer survivors treated with hyperfractionated TBI (total dose 1375 or 1500 cGy). Thirty individuals (18 men) were included in the study. The mean final height standard deviation score (s.d.s.) was -1.9 +/- 0.2, significantly lower than height s.d.s. at TBI (-0.2 +/- 0.2, P < 0.001). Final height s.d.s. was significantly correlated with age at diagnosis, age at TBI and target height (P = 0.04, P < 0.001, P < 0.001, respectively). Treatment with growth hormone (GH) (n = 7) maintained mean height s.d.s. at -2.0 from the onset of GH therapy until attainment of final height. The mean final sitting height s.d.s. was -2.2 +/- 0.2 (n = 16), significantly shorter than mean final standing height s.d.s. (P < 0.01). In conclusion, treatment with hyperfractionated TBI is associated with a reduction in standing height and an even greater reduction in sitting height. Final height after hyperfractionated TBI was similar to that reported after fractionated TBI.

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.

Lung transplantation after allogeneic marrow transplantation in pediatric patients: the Memorial Sloan-Kettering experience

BACKGROUND

Chronic lung disease and pulmonary failure are complications that can occur after bone marrow transplantation (BMT) and are associated with severe morbidity and mortality.

METHODS

We report on four patients who developed chronic, progressive, and irreversible lung disease 1 to 3 years after allogeneic BMT in childhood. These patients had chronic graft-versus-host disease (n=3) or radiation-related pulmonary fibrosis (n=1). Three patients underwent double lung transplants and one patient underwent a single lung transplant 2 to 14 years after BMT.

RESULTS

All four patients tolerated the lung transplantation procedure well and showed significant clinical improvement with normalization of pulmonary function tests by 1 year posttransplant. One patient died from infectious complications 3 years after lung transplantation, and one patient died after chronic rejection of the transplanted lungs 6 years posttransplant. Two patients remain alive without significant respiratory impairment 2 and 7 years after lung transplantation.

CONCLUSION

We conclude that lung transplantation offers a viable therapeutic option for patients who develop respiratory failure secondary to BMT.

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.

Stem cell transplantation for the treatment of Fanconi anaemia using a fludarabine-based cytoreductive regimen and T-cell-depleted related HLA-mismatched peripheral blood stem cell grafts

We have employed a new cytoreductive regimen to transplant two patients with Fanconi anaemia (FA), using T cell-depleted two HLA-allele disparate related peripheral blood stem cell transplants (PBSCTs). Patient 1, a 5-year-old male with FA and aplastic anaemia, initially received an HLA two-antigen mismatched unrelated cord blood transplant and failed to engraft. He received fludarabine (Flu) and cyclophosphamide (Cy), followed by a CD34(+) E-rosette(-) (CD34(+)E(-)), T cell-depleted, granulocyte colony-stimulating factor (G-CSF)-mobilized PBSCT from his HLA B-DRB1 mismatched father. He received anti-thymocyte globulin (ATG), steroids, FK506 and G-CSF after transplant for rejection and graft-versus-host disease (GVHD) prophylaxis. The patient is now 23 months after SCT with no evidence of GVHD and with full haematopoietic and immune reconstitution. Patient 2, a 10-year-old boy with FA and myelodysplastic syndrome, received single-dose total body irradiation (SDTBI), Flu and Cy followed by a CD34(+)E(-), T-cell-depleted, G-CSF-mobilized PBSCT from his HLA B-DRB1 mismatched sister. He also received ATG, steroids, FK506 and G-CSF after transplant. The patient is now 12 months after SCT in complete remission with no evidence of GVHD. Absolute neutrophil counts (ANC) of > 1 x 10(9)/l were achieved on day 11 and day 10 post transplant respectively. Both patients are fully engrafted. In summary, we report two successful T-cell-depleted stem cell transplants from mismatched related donors for the treatment of Fanconi anaemia, using a fludarabine-based cytoreduction. Both patients experienced minimal toxicity, rapid engraftment and no GVHD.

Rapid selection of antigen-specific T lymphocytes by retroviral transduction

Infusions of donor peripheral blood T cells can induce durable remissions of Epstein-Barr virus (EBV) lymphomas complicating marrow grafts, but they contain alloreactive T cells capable of inducing graft-versus-host disease. EBV-specific T-cell lines or clones avoid this problem but require 30 to 40 days of culture to establish. To accelerate the generation of EBV-specific T cells, we tested whether retroviral vectors, which only integrate in dividing cells, could be used to transduce and select antigen-reactive T cells early after sensitization to autologous EBV-transformed B cells. T cells were transduced with a dicistronic retroviral vector, NIT, which encodes low-affinity nerve growth factor receptor as an immunoselectable marker and herpes simplex virus thymidine kinase as a suicide gene, at different time points after sensitization. EBV-specific cytotoxic T lymphocyte precursor (CTLp) frequencies in purified NIT(+) T-cell fractions transduced on day 8 of culture were comparable to those of EBV-specific T-cell lines cultured for 30 days or more. Alloreactive CTLp frequencies were markedly reduced in the NIT(+) fraction relative to the untransduced T-cell population. NIT(+) fractions transduced on day 8 possessed more CD4(+) T cells than the cell lines at day 30 and exhibited the same selective pattern of reactivity against immunodominant antigens presented by specific HLA alleles. In contrast, T cells transduced with NIT 5 days after stimulation with mitogen and interleukin-2 were relatively depleted of T cells specific for autologous EBV-transformed cells. Thus, retroviral vectors may be used for rapid selection of viral antigen-reactive T cells depleted of alloreactive T cells.

T-cell depletion of bone marrow transplants for leukemia from donors other than HLA-identical siblings: advantage of T-cell antibodies with narrow specificities

T-cell depletion of donor marrow decreases graft-versus-host disease resulting from transplants from unrelated and human leukocyte antigen (HLA)-mismatched related donors. However, there are diverse strategies for T-cell-depleted transplantation, and it is uncertain whether any improve leukemia-free survival (LFS). To compare strategies for T-cell-depleted alternative donor transplants and to compare T-cell depleted with non-T-cell-depleted transplants, we studied 870 patients with leukemia who received T-cell-depleted transplants from unrelated or HLA-mismatched related donors from 1982 to 1994. Outcomes were compared with those of 998 non-T-cell-depleted transplants. We compared LFS using different strategies for T-cell-depleted transplantation considering T-cell depletion technique, intensity of pretransplant conditioning, and posttransplant immune suppression using proportional hazards regression to adjust for other prognostic variables. Five categories of T-cell depletion techniques were considered: narrow-specificity antibodies, broad-specificity antibodies, Campath antibodies, elutriation, and lectins. Strategies resulting in similar LFS were pooled to compare T-cell-depleted with non-T-cell-depleted transplants. Recipients of transplants T-cell depleted by narrow-specificity antibodies had lower treatment failure risk (higher LFS) than recipients of transplants T-cell depleted by other techniques. Compared with non-T-cell-depleted transplants (5-year probability +/- 95% confidence interval [CI] of LFS, 31% +/- 4%), 5-year LFS was 29% +/- 5% (P = NS) after transplants T-cell depleted by narrow-specificity antibodies and 16% +/- 4% (P <.0001) after transplants T-cell depleted by other techniques. After alternative donor transplantation, T-cell depletion of donor marrow by narrow-specificity antibodies resulted in LFS rates that were higher than those for transplants T-cell depleted using other techniques but similar to those for non-T-cell-depleted transplants. (Blood. 2000;95:3996-4003)

Longitudinal monitoring of immune reconstitution by CDR3 size spectratyping after T-cell-depleted allogeneic bone marrow transplant and the effect of donor lymphocyte infusions on T-cell repertoire

Delayed immune reconstitution after allogeneic bone marrow transplantation (BMT) with associated infection is a major cause of morbidity and mortality. We used third complementarity region (CDR3) size spectratyping as a tool for monitoring T-cell repertoire reconstitution in 19 patients over a median time of 40 months after T-cell-depleted allogeneic BMT for chronic myeloid leukemia (CML). Furthermore, the effect of donor lymphocyte infusions (DLI) for the treatment of relapse in 18 of the 19 patients was analyzed. All BMT recipients had irregular spectratypes in the first 3- to -6 months after transplant. These evolved to more normal patterns by 12 months after transplant and continued to improve thereafter. In approximately a third of the patients, it took 2 to 3 years for all spectratypes to normalize, whereas in the other two thirds, some abnormal spectratypes persisted even after several years. In 9 patients, there was no immediate change in the CDR3 size profiles after DLI. In 3 patients, spectratypes improved slightly after DLI, whereas in 6 patients, spectratypes became more restricted and irregular. Overall, T-cell spectratypes in BMT patients were characterized by instability over time and in patients with graft-versus-host disease (GVHD), this was even more exaggerated. Several factors, such as pre-BMT conditioning, T-cell depletion of the donor marrow, loss of thymic function in adults, exposure to infectious agents, GVHD, and immunosuppressive treatment, are likely contributors to the delay in T-cell-repertoire reconstitution. (Blood. 2000;95:3990-3995)

Disseminated toxoplasmosis following T cell-depleted related and unrelated bone marrow transplantation

More than 95% of reported cases of disseminated toxoplasmosis following BMT have occurred following an unmodified transplant. Most have been fatal, diagnosed at autopsy and without antemortem institution of specific therapy. From 1989 to 1999, we identified 10 cases of disseminated toxoplasmosis, in 463 consecutive recipients of a T cell-depleted (TCD) BMT. Transplants were from an unrelated donor (n = 5), an HLA-matched sibling (n = 4) or an HLA-mismatched father (n = 1). In 40%, both the donor and recipient had positive IgG titers against T. gondii pre-transplant; in 30%, only the recipient was sero-positive. Three recipients of an unrelated TCD BMT developed toxoplasmosis despite both donor and host testing negative pretransplant. All 10 patients presented with high grade fever. CNS involvement ultimately occurred in seven patients, with refractory respiratory failure and hypotension developing in nine. Eight of 10 cases were found only at autopsy, involving the lungs (n = 7), heart (n = 5), GI tract (n = 5), brain (n = 8), liver and/or spleen (n = 5). The only survivor, treated on the day of presentation with fever and headache, was diagnosed by detection of T. gondii DNA by polymerase chain reaction (PCR) performed on the blood and spinal fluid. This study demonstrates the similar incidence of toxoplasmosis following TCD BMT and that reported post T cell-replete BMT, and underscores the need for rapid diagnostic tests in an effort to improve outcome.

Stem cell transplantation in patients with severe congenital neutropenia without evidence of leukemic transformation

Severe congenital neutropenia (CN) (Kostmann syndrome) is a hematologic disorder characterized by a maturation arrest of myelopoiesis at the promyelocyte/myelocyte stage of development. This arrest results in severe neutropenia leading to absolute neutrophil counts (ANC) below 0.2 x 10(9)/L associated with severe bacterial infections from early infancy. Data on over 300 patients with CN collected by the Severe Chronic Neutropenia International Registry (SCNIR) beginning in 1994 indicate that more than 90% of these patients respond to recombinant human granulocyte-colony stimulating factor (r-HuG-CSF) treatment with an ANC greater than 1. 0 x 10(9)/L. For patients who are refractory to r-HuG-CSF treatment and continue to have severe and often life-threatening bacterial infections, hematopoietic stem cell transplantation is the only currently available treatment. We report on a total of 11 patients with CN reported to the SCNIR who underwent transplantation for reasons other than malignant transformation between 1976 and 1998. Of these patients, 8 were nonresponders or showed only partial response to r-HuG-CSF treatment with ongoing infections. Results from these patients suggest that transplantation of stem cells from an HLA-identical sibling is beneficial for patients refractory to r-HuG-CSF. (Blood. 2000;95:1195-1198)

Engraftment and growth of patient-derived retinoblastoma tumour in severe combined immunodeficiency mice

The development of an in vivo model of retinoblastoma could be important for studying its biological behaviour and developing novel therapeutic strategies. We examined the ability of patient-derived retinoblastoma cells to grow and disseminate in severe combined immunodeficiency CB-17-SCID mice after subcutaneous (s.c.) inoculation without conditioning treatment. 24/30 (80%) of patient-derived tumours engrafted and grew as s.c. nodules in SCID mice. Whilst most xenografted tumours appeared to be localised, by PCR assay a positive DNA band of human minisatellite region (YNZ.22) was determined in the bone marrow of 19/25 (76%), in the spleen of 14/25 (56%) and in the liver of 16/25 (64%) mice, respectively, indicating dissemination to distant organs. Cytogenetic analysis demonstrated i(6p) in 5/12 (42%) and trisomy 1 or 1q abnormalities in 8/12 (67%) of the xenografted tumour samples studied, respectively, suggesting that retinoblastoma tumour cells maintain their cytogenetic abnormalities following adoptive growth in SCID mice. In this report we demonstrate the ability to propagate human primary retinoblastoma cells in SCID mice after s.c. inoculation and suggest the possibility of using the SCID mouse model to study the intrinsic biological behaviour of human retinoblastoma and to develop novel therapeutic strategies in the treatment of this disease.