Biomedical subjects

M Mohty

Publications and source records attributed to M Mohty.

30 records · Page 2Linked to original sources

PubMed2003

Infectious complications following allogeneic HLA-identical sibling transplantation with antithymocyte globulin-based reduced intensity preparative regimen.

In the setting of reduced-intensity conditioning (RIC) regimens for allogeneic stem cell transplantation (allo-SCT), the epidemiology of transplant-related infections is still poorly defined. In 101 high-risk patients who received an HLA-identical sibling allo-SCT after RIC, including fludarabine, busulfan and antithymocyte globulin (ATG), we report during the first 6 months a cumulative incidence of positive CMV antigenemia of 42% (95% CI 32-52%), developing at a median of 37 (range 7-116) days without evidence of CMV disease (median follow-up, 434 days). The cumulative incidence of bacteremia was 25% (95% CI 17-33%), occurring at a median of 67 (range 7-172) days, while patients had recovered a full neutrophil count. In all, 65% of the bacteremia (95% CI 49-81%) were gram negative. The cumulative incidence of fungal infections was 8% (95% CI 3-13%), with a median onset of 89 (range 7-170) days. In multivariate analysis, stem cell source (bone marrow; P=0.0002) was significantly associated with the risk of positive CMV antigenemia, while higher doses of prednisone (>2 mg/kg) represented the major risk factor for bacteremia (P=0.0001). Infectious-related mortality was 5% (95% CI 1-9%), with aspergillosis being the principal cause. Collectively, these results suggest that prospective efforts are warranted to develop optimal antimicrobial preventive strategies after RIC allo-SCT.

ABO Blood-Group System↗

PubMed2002

Features of large granular lymphocytes (LGL) expansion following allogeneic stem cell transplantation: a long-term analysis.

Large granular lymphocyte (LGL) proliferation typically follows a chronic course during which major features are cytopenia and immune abnormalities. Elevated numbers of LGL were reported in a few cases following allogeneic stem cell transplantation (allo-SCT). In this report, we present a retrospective analysis of LGL cases that occurred following allo-SCT in a cohort of 201 consecutive patients transplanted over a period of 7 years. Six cases were identified and LGL expansion occurred more frequently following a reduced fludarabine and anti-T lymphocyte globulin-based preparative regimen (4 cases/49), than after a conventional myeloablative regimen (2 cases/152). Expansion of LGL was seen between 3 and 15 months following allo-SCT. Hematopoiesis, with mild to severe cytopenia, was a favored target for LGL. Autoimmune manifestations including polyarthritis and hypergammaglobulinemia were also observed. LGL proliferation was observed in the context of chronic antigenic stimulation associated with recurrent viral infections especially CMV. Moreover, five out of these six high risk patients achieved a long-term complete remission concomitant or following LGL expansion. These data suggest that LGL might be a subset of effector lymphocytes which may participate to the graft-versus-tumor effect.

Adult↗

PubMed2002

Identification of precursors of leukemic dendritic cells differentiated from patients with acute myeloid leukemia.

Dendritic cells (DC) can facilitate immune responses that might help in the induction of effective antitumor T cell responses. We reported previously that leukemic blasts from selected patients with acute myeloid leukemia (AML) were able to differentiate in vitro into cells with mature DC features. However, despite the use of a wide variety of cytokine combinations, leukemic DC could not be obtained from all AML patients. In this study, we investigated in a wide range of AML patients (n = 30), the nature and functional characteristics of the blast compartment that can be induced to acquire DC features in vitro. Our results demonstrate that leukemic DC generated in the presence of GM-CSF, IL-4 and matured with CD40L, are composed of two major subsets: DC derived from CD14(+) leukemic cells and leukemic DC derived from in vivo expanded circulating blood myeloid DC (MDC). Leukemic DC of both subsets exhibited DC morphology, had a phenotype of mature DC, and could induce a potent proliferative response of naive CD4(+) T cells. Moreover, both subsets produced large amounts of IL-12p70 and leukemic CD14(+)-derived DC could induce a potent Th1 response. These results can be considered as a prerequisite before the design of vaccine immunotherapy protocols for the adjuvant treatment of AML patients.

Acute Disease↗

PubMed2002

Leukemic dendritic cells: potential for therapy and insights towards immune escape by leukemic blasts.

Dendritic cells (DCs) are a system of potent antigen-presenting cells (APCs) specialized to initiate primary immune responses. DCs are considered important elements in the induction of specific antitumor cytotoxic effectors. At present, because of potential therapeutic implications, the critical role of DCs in cancer patients is under intensive investigation. Interactions between DCs and acute myeloid leukemia cells represent an attractive model for the study of DC physiology. Moreover, DCs can be a valuable therapeutic tool for the adjuvant treatment of leukemic patients. However, DC subsets in vivo may also be affected by leukemogenesis and may contribute to the escape of leukemia from immune control. The aim of this review is to shed further light on this paradoxical picture where the line between immune tolerance and immune defense is narrow.

Antigen Presentation↗

PubMed2002

Recovery of lymphocyte and dendritic cell subsets following reduced intensity allogeneic bone marrow transplantation.

Approaches using reduced conditioning regimens have been developed to obtain minimal procedure-related toxicity. Such novel therapeutic options are being explored with good preliminary results concerning feasibility and engraftment. However, many aspects remain under-evaluated and few data are available about immune and dendritic cell (DC) reconstitution after these highly immunosuppressive regimens. We present here our data in 20 patients receiving allogeneic bone marrow transplantation (allo-BMT) using a reduced preparative regimen. We evaluated in the first 3 months following allo-BMT, several immunological parameters including DC subsets, and compared these to historical results obtained in a group of myeloablative allo-BMT patients. We found an early recovery of leukocytes, CD8+ and NK lymphocytes. We also found a trend towards an improved B cell recovery. These results are somewhat in contrast to the altered immune recovery observed in the myeloablative setting. In addition, we found a significant early circulating DC recovery. Circulating blood DCs were also found to be of full donor origin as assessed by FISH in sex-mismatched pairs. Nevertheless, naive CD4 + CD45RA + T cells were found to be profoundly reduced following such regimens.Collectively, these data further enhance the overall benefits of reduced intensity regimens and the need for a stringent biological monitoring for assessment of the potential advantages of reduced intensity allo-BMT in comparison with conventional allo-BMT.

Adult↗

PubMed2001

Circulating blood dendritic cells from myeloid leukemia patients display quantitative and cytogenetic abnormalities as well as functional impairment.

Dendritic cells (DCs) are responsible for the initiation of immune responses. Two distinct subsets of blood DCs have been characterized thus far. Myeloid DCs (MDCs) and plasmacytoid monocytes (PDCs) were shown to be able to promote polarization of naive T cells. This study shows a dramatic quantitative imbalance in both circulating blood DC subsets in 37 patients with acute myeloid leukemias. Eleven patients (30%) displayed a normal quantitative profile (MDC mean, 0.37% +/- 0.21%; range, 0.01% to 0.78%; PDC mean, 0.21% +/- 0.24%; range, 0.04% to 0.62%), whereas 22 (59%) showed a tremendous expansion of MDCs (9 patients: mean, 16.76% +/- 14.03%; range, 1.36% to 41%), PDCs (4 patients: mean, 7.28% +/- 6.84%; range, 1% to 14%), or both subsets (9 patients: MDC mean, 10.86% +/- 12.36%; range, 1.02% to 37.1%; PDC mean, 4.25% +/- 3.78%; range, 1.14% to 13.04%). Finally, in 4 patients (11%), no DC subsets were detectable. Both MDC and PDC subsets exhibited the original leukemic chromosomal abnormality. Ex vivo, leukemic PDCs, but not leukemic MDCs, had impaired capacity for maturation and decreased allostimulatory activity. Also, leukemic PDCs were altered in their ability to secrete interferon-alpha. These data provide evidence that DC subsets in vivo may be affected by leukemogenesis and may contribute to leukemia escape from immune control.

Animals↗

PubMed2001

Reduced intensity conditioning: enhanced graft-versus-tumor effect following dose-reduced conditioning and allogeneic transplantation for refractory lymphoid malignancies after high-dose therapy.

Non-myeloablative regimens have been proven to allow engraftment following allogeneic stem cells transplantation (allo-SCT) with minimal procedure-related toxicity. Conventional allo-SCT may produce remissions in patients with relapsed and refractory lymphoid malignancies (LM) but these good results may be achieved at the cost of high treatment-related morbidity and mortality. Application of allo-SCT using less intensive regimens may temper the frequency of these complications, allowing a potent graft-versus-tumor effect (GVT). We present our data on 11 patients with LM receiving allo-SCT with a reduced regimen. Ten patients had received previous high-dose therapy, and were at high risk for toxicity, thus precluding the use of allo-SCT. A fludarabine and low-dose busulfan combination facilitated engraftment while exerting GVT. Hematological recovery was quick, and full donor T cell chimerism preceded acute GVHD. GVHD and infections were the major problems. Spontaneous acute GVHD occurred in eight patients (72%). Five patients (45%) achieved complete remission, and the GVT effect was closely associated with GVHD. These results support the concept that GVT is effective against LM in patients who have been heavily pretreated. Further studies are needed to investigate strategies to generate more specific alloreactive effects providing optimal GVT and an acceptable risk of GVHD and infections.

Acute Disease↗

PubMed2001

Large granular lymphocytes (LGL) following non-myeloablative allogeneic bone marrow transplantation: a case report.

We report here the first case of large granular lymphocytes (LGL) expansion following non-myeloablative allo-BMT for chronic myeloid leukemia. We characterized the morphologic, phenotypic and functional features of the LGL subset amplified in vivo 14 months after allo-BMT. Our results indicate that LGL can mediate in vitro a cytolytic activity on tumor cells. In vivo, the timing of the LGL expansion was associated with a sustained complete molecular remission. These observations suggest that LGL are a subset with the properties of effector lymphocytes which may contribute to the graft-versus-tumor effect.

Bone Marrow Transplantation↗

PubMed2001

Autologous peripheral blood stem cell transplantation following heart transplantation for primary systemic amyloidosis.

A 47 years old woman was admitted with severe congestive heart failure. Cardiac echography showed increased intra-ventricular septum thickness, and there was a serum Ig G lambda monoclonal component. Cardiac biopsies confirmed diffuse amyloidosis of Al type. To avoid cardiac toxicity of chemotherapy, the patient received first a heart transplantation (HT), followed six months later by melphalan 200 mg/m(2) and autologous peripheral blood stem cell support (PBSCT). This case suggests that such strategy is feasible with a favorable outcome, and HT may be an appropriate procedure for some patients with Al amyloidosis who meet the criteria for PBSCT.

Amyloidosis↗

PubMed2000

High rate of secondary viral and bacterial infections in patients undergoing allogeneic bone marrow mini-transplantation.

New approaches using nonmyeloablative-conditioning regimens have been developed to cause minimal procedure-related toxicity. Such novel therapeutic options are being explored with good preliminary results concerning feasibility and engraftment. However many aspects remain under-evaluated, and few data are available about viral and nonviral infections after these highly immunosuppressive regimens. We present our preliminary data on 21 patients receiving a highly immunosuppressive conditioning strategy, focusing on early infectious complications. Early viral infections before day 45, especially CMV, occurred at a high rate (65%). Furthermore, 33% of patients presented with late bacterial infections (predominately gram negative) although they were not neutropenic compared to conventional conditioning regimens. Although there is presently real interest in these new conditioning regimens which result in reduced immediate transplant-related mortality, it is important that investigators be aware of these pitfalls which may secondarily increase transplant toxicity. Further studies are needed to confirm these findings.

Adult↗

PubMed2000

CD34(+) immunoselected cells for poor graft function following allogeneic BMT.

BACKGROUND: Poor graft function without signs of graft rejection following allogeneic BMT (allo-BMT) occurs in around 9% of patients. A high incidence of hazardous complications may be encountered, leading to life-threatening situations. METHODS: We describe three patients who underwent allo-BMT for acute leukemia in first complete remission and untreated myelodysplastic syndrome. The three patients experienced prolonged and profound granulocytopenia, anemia and thrombocytopenia, despite growth factors and transfusions. This was not corrected by donor leukocytes infusion. They received a boost of CD34(+) positively-selected cells from their HLA-identical sibling donors. RESULTS: A rapid improvement of peripheral blood cell counts was observed in both patients who were in full donor chimerism status at time of boost infusion, whereas the patient with mixed chimerism did not show any signs of improvement. Neither patient suffered further exacerbation of GvHD. DISCUSSION: Allogeneic positively-immunoselected CD34(+) cells can represent an interesting alternative treatment for poor graft function following allo-BMT, in the absence of graft rejection signs.

Adult↗

PubMed2000

Carboxypeptidase G2 rescue in delayed methotrexate elimination in renal failure.

We report here the case of a 68-year-old woman who presented severe renal failure following the first cycle of high dose methotrexate (HDMTX) for the treatment of a cerebral malignant lymphoma. Before HDMTX administration, serum creatinine value was normal and three days after HDMTX, it reached 457 micromol/L. Leucovorin rescue, hemodialysis and cholestyramine did not increase MTX clearance. Because of the persistence of renal failure, and the high risk of important hematological side-effects associated with high MTX plasma levels, the patient received carboxypeptidase G2 (CPDG2). This allowed MTX plasma levels to decrease by 80% in 15 minutes. No side effects were observed and renal function normalized rapidly. In some patients, when high-dose leucovorin associated with hemodialysis and cholestyramine are unable to restore normal MTX clearance, CPDG2 should be considered because it may represent a safe and efficient alternative for the management of MTX intoxication.

Aged↗