Biomedical subjects

Mitchell E Horwitz

Publications and source records attributed to Mitchell E Horwitz.

10 recordsLinked to original sources

PubMed2006

Patients with chronic granulomatous disease have a reduced peripheral blood memory B cell compartment.

In this study, we have identified an altered B cell compartment in patients with chronic granulomatous disease (CGD), a disorder of phagocyte function, characterized by pyogenic infections and granuloma formation caused by defects in NADPH activity. This is characterized by an expansion of CD5-expressing B cells, and profound reduction in B cells expressing the memory B cell marker, CD27. Both findings were independent of the age, genotype, and clinical status of the patients, and were not accompanied by altered CD5 and CD27 expression on T cells. Focusing on CD27-positive B cells, considered to be memory cells based on somatically mutated Ig genes, we found that the reduction was not caused by CD27 shedding or abnormal retention of CD27 protein inside the cell. Rather, it was determined that CD27-negative B cells were, appropriately, CD27 mRNA negative, consistent with a naive phenotype, whereas CD27-positive B cells contained abundant CD27 mRNA and displayed somatic mutations, consistent with a memory B cell phenotype. Thus, it appears that CGD is associated with a significant reduction in the peripheral blood memory B cell compartment, but that the basic processes of somatic mutation and expression of CD27 are intact. X-linked carriers of CGD revealed a significant correlation between the percentage of CD27-positive B cells and the percentage of neutrophils with normal NADPH activity, reflective of the degree of X chromosome lyonization. These results suggest a role for NADPH in the process of memory B cell formation, inviting further exploration of secondary Ab responses in CGD patients.

Adolescent↗

PubMed2006

Polyclonal long-term MFGS-gp91phox marking in rhesus macaques after nonmyeloablative transplantation with transduced autologous peripheral blood progenitor cells.

We have recently reported that the RD114-pseudotyped MFGS-gp91phox vector achieves unprecedented levels of correction of the NADPH-oxidase gp91phox (approved gene symbol CYBB) defect in CD34(+) cells from patients with X-linked chronic granulomatous disease in the NOD/SCID mouse model. Considering clinical use of this vector, we transplanted autologous mobilized peripheral blood CD34(+) progenitor cells, transduced with the RD114-MFGS-gp91phox vector, into two healthy rhesus macaques following nonmyeloablative conditioning. The moderately high levels of in vivo marking seen in the first months following transduction decreased and stabilized at about 8 months posttransplant. Marking for both healthy animals after 15 months was 0.3 to 1.3 vector copies per 100 cells in lymphocytes, neutrophils, and monocytes. Vector insertion analyses performed by linear amplification-mediated PCR and sequencing identified 32 and 45 separate insertion sites in the animals. Identical insertion sites were found in myeloid cells and lymphocytes, demonstrating the successful transduction of lymphomyeloid progenitors. Some inserts landed in the vicinity of genes controlling cell cycle and proliferation. Statistical analyses of insertion sites 1 year posttransplant suggest a high diversity of insertion sites despite low marking.

Animals↗

PubMed2006

Unique abnormalities of CD4(+) and CD8(+) central memory cells associated with chronic graft-versus-host disease improve after extracorporeal photopheresis.

Chronic graft-versus-host disease (cGVHD) remains a problematic complication of allogeneic hematopoietic stem cell transplantation. Laboratory parameters correlated with cGVHD have not been fully defined, although changes in CD4/CD8 ratios occur and a decrease in CD4(+) central memory T cells has been noted. Extracorporeal photopheresis (ECP) is an effective therapy for steroid-refractory cGVHD. We have noted changes in lymphocyte subsets after ECP. CD4(+) and CD8(+) T-cell central and effector memory populations were enumerated by flow cytometry in a cohort of 37 patients postallogeneic transplantation with symptomatic cGVHD. Of the patients with symptomatic cGVHD, 7 were treated with ECP over 6 months and prospectively assessed for changes in lymphocyte subsets. There was a highly significant correlation of an increase in CD8(+) central memory cells and a concomitant decrease in CD4(+) central memory cells in patients with symptomatic cGVHD. These changes were not detected in patients without cGVHD posttransplantation. In all, 7 patients with cGVHD followed up prospectively during ECP treatment showed a statistically significant normalization of the pattern of CD4(+) and a trend toward normalization of CD8(+) central memory T cells coincident with improvement of cGVHD. These data indicate a high correlation between disturbances in the balance of central and effector memory populations and cGVHD suggesting use in following up responses to therapy. The normalization of central and effector memory populations in response to ECP coincident with clinical improvement of cGVHD support a correlation between these laboratory parameters and cGVHD. Further studies are needed to demonstrate whether laboratory measurements of the magnitude of changes in central and effector memory populations are useful prognostically or can be used to guide response to therapy. The contrasting change in central memory cells (CD8(+) increased versus CD4(+) decreased) in cGVHD provide support for recent reports suggesting unique differences in the differentiation pathways for CD8(+) versus CD4(+) T cells.

Adult↗

PubMed2005

Chronic graft-versus-host disease.

Chronic graft versus host disease (GVHD) remains today one of the most vexing late complications of allogeneic stem cell transplantation. Occurring a minimum of 100 days following stem cell transplantation, approximately 50% of patients will experience some degree of chronic GVHD. Host-reactive lymphocytes of donor origin are the cells responsible for the "alloimmune" attack. The increased use of hematopoietic stem cells collected from the peripheral blood instead of bone marrow and the increasing age of stem cell transplant recipients has led to a higher incidence of chronic GVHD. Chronic GVHD most commonly affects the skin, liver, eyes or the mouth, however multiple other sites may also be affected. Chronic GVHD and the medications used to treat it result in a profoundly immunocompromised state. Death due to severe chronic GVHD is usually a consequence of infectious complications. Standard treatment for severe chronic GVHD is a combination of cyclosporine and prednisone. An alternating day regimen of these two agents prolongs survival and reduces drug-related adverse events. Topical therapy to affected areas is preferred for patients with mild disease. The 10-year survival of patients with mild chronic GVHD is approximately 80%, but is less than 5% for patients affected by severe chronic GVHD.

CD4-Positive T-Lymphocytes↗

PubMed2004

Severe chronic graft-versus-host disease is characterized by a preponderance of CD4(+) effector memory cells relative to central memory cells.

Donor alloreactive CD4(+) T cells are important to the pathogenesis of chronic graft-versus-host disease (cGVHD), but specific subsets of CD4(+) T cells responsible for GVHD have not been defined. We hypothesized that cGVHD might be associated with a preponderance of CD4(+) effector memory cells (CCR7(-)/CD62L(low), CD4(EM)). We analyzed CCR7 and CD62L expression on CD4(+) T cells from stem cell transplantation patients, who did or did not develop cGVHD, and healthy donors. Patients with cGVHD had a higher percentage of CD4(EM) cells (35.5% +/- 2.9%) than healthy donors (13.8% +/- 0.7%; P <.0001) or patients without cGVHD that received a transplant (21.7% +/- 2.1%; P <.01). Using corticosteroid dose as a surrogate marker for cGVHD severity, severe cGVHD was associated with a higher percentage of CD4(EM) cells. The proportion of CD4(EM) cells in corticosteroid-dependent patients with systemic lupus erythematosis or Wegener granulomatosis did not differ from patients without cGVHD that received a transplant. This finding implies that overrepresentation of CD4(EM) cells is a unique feature of cGVHD.

CD4-Positive T-Lymphocytes↗

PubMed2004

Hematopoietic stem cell transplantation for complete IFN-gamma receptor 1 deficiency: a multi-institutional survey.

OBJECTIVES: To evaluate the outcome of hematopoietic stem cell transplantation (HSCT) in a series of patients with inherited complete IFN-gamma receptor 1 (IFNgammaR1) deficiency. STUDY DESIGN: We report 8 patients who received altogether 11 HSCT from family donors, including 10 HLA-identical (5 siblings and 5 relatives) and 1 HLA-haplo-identical donors. Five grafts were T-cell depleted, and conditioning regimens varied in intensity. RESULTS: Four patients died within 8 months after HSCT. Two of these deaths were due to specific complications related to mycobacterial infection. There was no or very low (2%) donor cell engraftment in 2 survivors. Only 2 patients are in full remission of mycobacterial disease 5 years after HSCT. These are the only patients who received non-T-cell-depleted grafts from an HLA-identical sibling after a fully myeloablative conditioning regimen. CONCLUSIONS: HSCT can lead to prolonged remission of mycobacterial disease in children with complete IFNgammaR1 deficiency. However, optimal control of mycobacterial infection before HSCT and the use of a non-T-cell-depleted transplant from an HLA-identical sibling after a fully myeloablative conditioning regimen are recommended.

Child↗

PubMed2004

Pediatric large-volume leukapheresis: a single institution experience with heparin versus citrate-based anticoagulant regimens.

BACKGROUND: Anticoagulant-associated toxicity may exert significant effects on the safety and efficacy of large-volume leukapheresis (LVL) in children, however, few studies specifically address management of this issue. STUDY DESIGN AND METHODS: Seventy-four consecutive LVL procedures (mean, 4 blood volumes processed) in children weighing less than or equal to 30 kg (minimum, 10.9 kg) were analyzed. The first 21 procedures were evaluated retrospectively; 11 used heparin alone (Group I) and 10 used heparin plus reduced-dose ACD-A (whole blood to anticoagulant ratio > or =20:1) (Group II). The next 53 procedures were evaluated prospectively and used full-dose ACD-A (whole blood to anticoagulant ratio < or =13:1), intravenous divalent cation prophylaxis and no heparin; 11 used calcium alone (Group III) followed by 42 with calcium plus magnesium (Group IV). RESULTS: Seventy-four LVL (56 PBPC and 18 MNC) collections were performed in 38 subjects. One donor in Group I experienced a significant groin hematoma at the site of line placement. One donor each in Groups III and IV had mild paresthesias. Despite a mean citrate infusion rate of 2.6 mg per kg per minute, mean postapheresis serum potassium and ionized magnesium and calcium concentrations in Group IV declined by only 9, 8, and 4 percent, respectively, and stable levels of these variables were maintained 24 hours later. Postapheresis PLT counts declined significantly from baseline preapheresis levels in all groups (mean, 52% decrease). CONCLUSIONS: Use of full-dose citrate anticoagulant with prophylactic intravenous divalent cation infusion offers an effective and safe approach to management of anticoagulant-related toxicity in children undergoing LVL.

Adolescent↗

PubMed2003

Concentrated RD114-pseudotyped MFGS-gp91phox vector achieves high levels of functional correction of the chronic granulomatous disease oxidase defect in NOD/SCID/beta -microglobulin-/- repopulating mobilized human peripheral blood CD34+ cells.

In previous studies amphotropic MFGS-gp91phox (murine onco-retrovirus vector) was used in a clinical trial of X-linked chronic granulomatous disease (X-CGD) gene therapy to achieve transient correction of oxidase activity in 0.1% of neutrophils. We later showed that transduced CD34+ peripheral blood stem cells (CD34+ PBSCs) from this trial transplanted into nonobese diabetic/severe combined immunodeficient (NOD/SCID) mice resulted in correction of only 2.5% of human neutrophils. However, higher rates of transduction into stem cells are required. In the current study we demonstrate that the same vector (MFGS-gp91phox) pseudo-typed with RD114 envelope in a 4-day culture/transduction regimen results in a 7-fold increase in correction of NOD/SCID mouse repopulating X-CGD CD34+ PBSCs (14%-22% corrected human neutrophils; human cell engraftment 13%-67%). This increase may result from high expression of receptor for RD114 that we demonstrate on CD34+CD38- stem cells. Using RD114-MFGS encoding cyan fluorescent protein to allow similar studies of normal CD34+ PBSCs, we show that progressively higher levels of gene marking of human neutrophils (67%-77%) can be achieved by prolongation of culture/transduction to 6 days, but with lower rates of human cell engraftment. Our data demonstrate the highest reported level of functional correction of any inherited metabolic disorder in human cells in vivo with the NOD/SCID mouse system using onco-retrovirus vector.

Animals↗

PubMed2003

Persistent Mycobacterium avium infection following nonmyeloablative allogeneic peripheral blood stem cell transplantation for interferon-gamma receptor-1 deficiency.

Interferon-gamma receptor-1 (IFNgammaR1) deficiency is a rare inherited immunodeficiency. We performed a nonmyeloablative allogeneic stem cell transplantation on a boy with complete IFNgammaR1 deficiency and refractory disseminated Myco- bacterium avium infection. Despite the patient's profound immune defect, early donor stem cell engraftment was low. Full donor engraftment was accomplished only following multiple donor lymphocyte infusions. Detection of IFNgammaR1 expression on peripheral blood monocytes and neutrophils corresponded with establishment of stable, complete donor hematopoietic chimerism. However, expression of, and signaling through IFNgammaR1 disappeared shortly thereafter. Disseminated Mycobacterium avium infection persisted and the patient died. Coculture of Myco- bacterium avium with normal myeloid cells resulted in an IFNgamma signaling defect similar to that observed in vivo. Active disseminated Mycobacterium avium infection may significantly compromise normal immune reconstitution following allogeneic stem cell transplantation. Patients with IFNgammaR1 deficiency should receive transplants before developing refractory mycobacterial infections.

Child, Preschool↗

PubMed2002

Immunomodulation in stem-cell transplantation.

Acute graft-versus-host disease is a complication that affects 30-60% of patients undergoing allogeneic stem-cell transplantation. The standard for prophylaxis for graft-versus-host disease has historically been the combination of cyclosporine and methotrexate. Recently, tacrolimus has been used more frequently and current studies are exploring the potential of mycophenolate mofetil. There is little published experience with the use of sirolimus in prophylaxis or treatment but studies are ongoing. There have been significant advances recently in the treatment of steroid-refractory acute graft-versus-host disease. Historically, antithymocyte globulin was used when patients did not respond to the steroid treatment. New monoclonal antibodies such as daclizumab, and tumor necrosis factor alpha inhibitors such as infliximab are producing more promising results. Chronic graft-versus-host disease continues to be a major complication of stem-cell transplantation, affecting 35-50% of patients. Finding effective treatments for chronic graft-versus-host disease other than steroids continues to be a challenge.

Adjuvants, Immunologic↗