Graft-versus-Host Disease in Mini-transplant

Promising role of reduced-toxicity hematopoietic stem cell transplantation (PART-I)

Allogeneic hematopoietic stem cell transplantation (HSCT) remains a potential curative option for many patients with hematological malignancies (HM). However, the high rate of transplantation-related mortality (TRM) restricted the use of standard myeloablative HSCT to a minority of young and fit patients. Over the past few years, it has become evident that the alloreactivity of the immunocompetent donor cells mediated anti-malignancy effects independent of the action of high dose chemoradiotherapy. The use of reduced intensity conditioning (RIC) regimens has allowed a graft-versus-malignancy (GvM) effect to be exploited in patients who were previously ineligible for HSCT on the grounds of age and comorbidity. Retrospective analysis showed that RIC has been associated with lower TRM but a higher relapse rate leading to similar intermediate term overall and progression-free survivals when compared to standard myeloablative HSCT. However, the long term antitumor effect of this approach is less well established. Prospective studies are ongoing to define which patients might most benefit from reduced toxicity stem cell transplant (RT-SCT) and which transplant protocols are suitable for the different types of HM. The advent of RT-SCT permits the delivery of a potentially curative GvM effect to the majority of patients with HM whose outcome with conventional chemotherapy would be dismal. Remaining challenges include development of effective strategies to reduce relapse rates by augmenting GvM effects without increasing toxicity.

Trends in the prevalence of invasive fungal infections from an analysis of annual records of autopsy cases of Toho University

Clinical diagnosis of invasive fungal infections (IFIs) is sometimes difficult, and obtaining an accurate assessment of trends concerning the prevalence of IFIs is a challenge. The aim of this study was to determine trends in the prevalence of IFIs from an autopsy survey. The retrospective review of autopsy records stored in Toho University was performed on all documented cases with fungal infection from 1955 to 2006. A total of 411 cases of IFIs were detected among 10 297 autopsies. The prevalence of candidiasis decreased from 3.6% (1981-93) to 2.0% (1994-2006), and that of aspergillosis increased throughout the 52-year period and reached 2.0% (1994-2006). The prevalence of IFIs in the patient group comprising haematological disorders was significantly higher (19.9%) than in other patient groups (2.9%), of which the odds ratio was 18.4 for mucormycosis and 10.0 for aspergillosis. The lung was the most common organ involved irrespective of major fungal species, and most cases with candidiasis showed multiple-organ infection. Results confirmed the increasing prevalence of aspergillosis and high risk of IFIs in the patient group with haematological disorders. IFIs were also detected in an immunocompromised state caused not only by primary disease but also by treatment with anti-tumour drugs and corticosteroids.

CD3+/Tregs ratio in donor grafts is linked to acute graft-versus-host disease and immunologic recovery after allogeneic peripheral blood stem cell transplantation

Graft-versus-host disease (GVHD), mediated by mature T cells present in the donor graft, remains a major complication after allogeneic peripheral blood stem cell transplantation (PBSCT). Regulatory T cells (Tregs) (CD4(+)CD25(high)Foxp3(+)) are believed to maintain tolerance and to inhibit GVHD after allogeneic PBSCT (allo-PBSCT). In this study, we analyzed the graft CD3(+)/Tregs ratio (gCD3/Tregs R) and evaluated its impact on acute GVHD (aGVHD) and immunologic recovery after myeloablative allo-PBSCT. We analyzed 65 consecutive patients who underwent transplantation with unmanipulated peripheral blood stem cells from an HLA-identical related donor (n = 45) or an HLA-identical unrelated donor (n = 20). The median CD3(+) and Tregs doses administered were 256 × 10(6)/kg of body weight (range, 67-550 × 10(6)/kg) and 12 × 10(6)/kg (range, 2-21 × 10(6)/kg), respectively; the median gCD3/Tregs R value was 18 (range, 8-250). Patients were subdivided into a high gCD3/Tregs R (≥36) group (HR; n = 26) and a low gCD3/Tregs R (<36) group (LR; n = 39). The incidence of aGVHD (grade II-IV) was lower in the LR group compared with the HR group (8/39 [20%] versus 22/26 [84%]; P < .001). Median cytomegalovirus-specific CD8(+) T lymphocytes were significantly higher in the LR group than in the HR group at 1 month (2 cells/μL versus 0 cells/μL; P < .001), 2 months (6 cells/μL versus 1 cell/μL; P < .001), and 3 months (15 cells/μL versus 3 cells/μL; P < .001) months. Moreover, cytomegalovirus infection/disease was observed in 15% of patients in the LR group versus 69% of patients in the HR group (P < .001). At multivariate logistic regression, gCD3/Tregs R was correlated both with aGVHD (odds ratio, 2.50; 95% confidence interval, 1.30-4.50; P = .05) and with cytomegalovirus infection/disease (odds ratio, 2.35; 95% confidence interval, 0.9-5.00; P = .05). Taken together, our data may suggest that the balance in favor of graft Tregs content is able to mediate protective effects against aGVHD and to maintain an optimal microenviroment for the reconstitution of functional immunity.

Regulatory T-Cells in the Graft and the Risk of Acute Graft-Versus-Host Disease After Allogeneic Stem Cell Transplantation

BACKGROUND

FOXP3+ regulatory T-cells (Treg) are important regulators of allo-reactivity and may therefore represent an important predictor for the risk of graft versus-host disease (GVHD) after allogeneic stem cell transplantation.

METHODS

To determine the clinical significance of Treg-content in stem cell grafts, we analyzed 58 human leukocyte antigen (HLA)-identical sibling donors (34 patients received myeloablative and 24 patients reduced intense conditioning regimens) and correlated the Treg frequency with clinical outcome after stem cell transplantation (SCT).

RESULTS

A mean value of 9.1 x 10(6) CD4+ FOXP3+ Treg per kg body weight (bw) of the recipient was transplanted (ranging from 0.7 to 33.7 x 10(6) Treg/kg bw). Graft content of Treg correlated with mononuclear cells and CD3+ T-cells. Patients receiving low numbers of Treg (Treg(low)) after myeloablative conditioning for SCT had a significantly increased cumulative incidence of 76% for acute GVHD when compared with 23% for individuals receiving high numbers of Treg (Treg(high)). This observation, however, was not made in patients after reduced intense conditioning-SCT. Notably, relapse rate was not significantly different between Treg(low) and Treg(high) patients in either patient group and overall survival was even increased in Treg(high) patients after myeloablative SCT. Finally, low Treg graft levels represent an independent prognostic factor in multivariate analysis for the appearance of acute GHVD.

CONCLUSION

Donor-derived Treg might be of particular significance for the development of acute GVHD after myeloablative SCT using HLA-identical sibling donors.

Stem cell transplantation with reduced-intensity conditioning regimens: a review of ten years experience with new transplant concepts and new therapeutic agents

The realization in the 1990s that allogeneic stem cell transplants (SCT) have a potentially curative graft-versus-leukemia (GVL) effect in addition to the antileukemic action of myeloablative conditioning regimens was a major stimulus for the development of reduced-intensity conditioning (RIC) regimens, aimed primarily at securing engraftment to provide the GVL effect, while minimizing regimen-related toxicity. It is now over 10 years since RIC regimens were heralded as a new direction in the field of SCT. Over the last decade much has been learned about the ways in which the conditioning regimen can be tailored to provide adequate immunosuppression, and modulated to deliver a chosen degree of antimalignant treatment. The huge literature of clinical data with RIC transplantation now permits us to more clearly define the success and limitations of the approach. This review examines the origins of RIC SCT, explores the degree to which the initial expectations and purpose of the approach have been realized, and outlines some ways forward for the field.

Reduced-intensity conditioning for acute myeloid leukemia: is this strategy correct

Allogeneic stem cell transplantation for acute myeloid leukemia (AML) using reduced-intensity conditioning (RIC) is based on the strategy of attaining donor cell engraftment with immunosuppressive agents. This approach, which relies predominantly on donor effector cells for anti-leukemic or graft-versus-leukemia effect, is being used with increased frequency. Treatment-related mortality appears less with RIC than that observed with conventional myeloablative regimens. Available data support the fact that a myeloablative regimen is not required for successful engraftment and some patients appear to be cured of their disease. Despite the plethora of clinical reports, however, no prospective studies have been conducted that establish this procedure as the preferred option in AML. On the other hand, patients formerly excluded from a myeloablative procedure such as the 'elderly' and those with significant comorbid conditions, often may be RIC transplant candidates. By using prospective controlled clinical trials, we will determine whether these encouraging RIC data are applicable to a nonselect population of AML. The transplant community now is poised to design and complete investigations to ascertain the true role of RIC in the treatment of AML.

An Irradiation-Free Nonmyeloablative Bone Marrow Transplantation Model: Importance of the Balance between Donor T-cell Number and the Intensity of Conditioning

BACKGROUND

Animal allogeneic bone marrow transplantation (BMT) models with nonmyeloablative conditioning regimens have so far required irradiation or antibodies in addition to immunosuppressive drugs for engraftment. Moreover, although it is known that the balance between donor T-cell number and the dose of immunosuppressive drugs would be critical for engraftment, it has not been experimentally clarified in a nonmyeloablative regimen.

METHODS

We used C57BL/6 mice as donors and DBA/2 mice as recipients with a nonmyeloablative regimen including fludarabine (Flu) and cyclophosphamide (CPA) without irradiation or antibodies. To determine the adequate doses, we injected recipients with various doses of Flu and CPA, and 2x10 bone marrow cells (BMC) and 5x10 splenocytes (SC). Furthermore, using T-cell-depleted BMC and enriched T cells, we investigated the balance between donor T-cell number and the dose of Flu.

RESULTS

Doses of Flu at 150 mg/kg/dayx6 and CPA at 150 mg/kg/dayx2 were most appropriate for engraftment with low mortality. All mice appropriately pretreated and transplanted with both BMC and SC exhibited complete donor chimeras. Donor cell engraftment was not enhanced by any increase of BMC transplanted, and dose escalation of donor T cells but not BMC led to the reduction of Flu dose required for engraftment of donor cells.

CONCLUSIONS

We have established a murine nonmyeloablative BMT model in a fully MHC-mismatched combination for donor cell engraftment with complete donor chimerism. Simultaneously, we have quantitatively demonstrated that the balance between donor T-cell number and the dose of immunosuppressive drugs is critical for stable engraftment.

Reduced-intensity allogeneic hematopoietic stem cell transplantation for acute leukemias: ‘what is the best recipe?’

Reduced-intensity stem cell transplantation (RIST) has been shown to be a safe and useful alternative transplant method for patients including elderly and medically unfit patients. RIST conditioning regimens vary widely in the intensity of myeloablation, immunoablation, and antileukemia effects, and thus optimal regimen for each disease entity is yet to be determined. Most reports on RIST to date are small, single-institution experiences or retrospective studies with heterogeneous patient populations and primary diseases, complicating any direct comparison between studies. In acute myeloid leukemia (AML), moderate-intensity regimens may be effective, achieving 30-70% 1-year disease-free survival in various series, but minimal-intensity regimens are associated with high relapse rates. In acute lymphoblastic leukemia (ALL), not even moderate-intensity regimens are effective and most patients with advanced ALL relapse post transplant. Thus, the risk/benefit ratios of graft-versus-host disease/graft-versus-leukemia effect differ among diseases. Larger, prospective, multi-center clinical trials are needed to determine the best use of RIST in hematologic malignancies.