title: Add-back of allodepleted donor T cells to improve immune reconstitution after haplo-identical stem cell transplantation.
abstract: Poor immune reconstitution after haplo-identical stem cell transplantation results in high mortality from viral infections and relapse. One approach to overcome this problem is to deplete alloreactive cells selectively by deleting T cells activated by recipient stimulators, using an immunotoxin directed against the activation marker CD25. However, the degree of depletion of alloreactive cells is variable following stimulation with recipient PBMC, and this can result in GvHD. We have shown that using recipient EBV-transformed LCL as stimulators to activate donor alloreactive T cells results in more consistent depletion of in vitro alloreactivity while preserving T-cell responses to viral and potential myeloid tumor Ag. Based on these data, we have embarked on a phase I clinical dose escalation study of add-back of allo-LCL-depleted donor T cells in the haplo-identical setting, to determine if the allodepletion we achieve to allow infusion of sufficient T cells to restore useful antiviral/anti-leukemic responses without causing GvHD. Fifteen patients have so far been treated. The incidence of significant acute or chronic GvHD has been low (2/15), as has mortality from infection (1/15). Preliminary data show accelerated immune reconstitution in dose level 2 patients. Infused allodepleted donor T cells appear able to expand significantly in the face of viral reactivations, and doses as low as 3 x 10(5)/kg may be sufficient to confer useful antiviral immunity in this setting. At a median follow-up of 19.5 months, nine of 15 patients are alive and disease-free. Five patients have relapsed, all of whom have died.
authors.affiliation: Dept. of Bone Marrow Transplantation, Great Ormond Street Children's Hospital, London WC1N 3JH, UK.
authors.forename: P J
authors.initials: PJ
authors.lastname: Amrolia
authors.forename: G
authors.initials: G
authors.lastname: Mucioli-Casadei
authors.forename: H
authors.initials: H
authors.lastname: Huls
authors.forename: H E
authors.initials: HE
authors.lastname: Heslop
authors.forename: J
authors.initials: J
authors.lastname: Schindler
authors.forename: P
authors.initials: P
authors.lastname: Veys
authors.forename: E S
authors.initials: ES
authors.lastname: Vitetta
authors.forename: M K
authors.initials: MK
authors.lastname: Brenner
mesh_terms: D017321:Clinical Trials, Phase I as Topic; D020031:Epstein-Barr Virus Infections / Q000276:immunology / Q000517:prevention & control; D020544:Graft vs Leukemia Effect / Q000276:immunology; D006239:Haplotypes / Q000276:immunology; D006801:Humans; D008212:Lymphocyte Depletion / Q000379:methods*; D015337:Multicenter Studies as Topic; D020127:Recovery of Function / Q000276:immunology; D033581:Stem Cell Transplantation; D013601:T-Lymphocytes / Q000276:immunology / Q000637:transplantation*; D014184:Transplantation, Homologous