Interleukin-7 induced facilitation of immunological reconstitution of sublethally irradiated mice following treatment with alloreactive spleen cells in a murine model of B-cell leukemia/lymphoma (BCL1)

Interleukin-21 promotes thymopoiesis recovery following hematopoietic stem cell transplantation

BACKGROUND

Impaired T cell reconstitution remains a major deterrent in the field of bone marrow (BM) transplantation (BMT) due to pre-conditioning-induced damages inflicted to the thymi of recipient hosts. Given the previously reported thymo-stimulatory property of interleukin (IL)-21, we reasoned that its use post-BMT could have a profound effect on de novo T cell development.

METHODS

To evaluate the effect of IL-21 on de novo T cell development in vivo, BM derived from RAG2p-GFP mice was transplanted into LP/J mice. Lymphocyte reconstitution was first assessed using a hematological analyzer and a flow cytometer on collected blood samples. Detailed flow cytometry analysis was then performed on the BM, thymus, and spleen of transplanted animals. Finally, the effect of human IL-21 on thymopoiesis was validated in humanized mice.

RESULTS

Using a major histocompatibility complex (MHC)-matched allogeneic BMT model, we found that IL-21 administration improves immune reconstitution by triggering the proliferation of BM Lin^-Sca1⁺c-kit⁺ (LSK) subsets. The pharmacological effect of IL-21 also culminates in the recovery of both hematopoietic (thymocytes) and non-hematopoietic (stromal) cells within the thymi of IL-21-treated recipient animals. Although T cells derived from all transplanted groups proliferate, secrete various cytokines, and express granzyme B similarly in response to T cell receptor (TCR) stimulation, full regeneration of peripheral naïve CD4⁺ and CD8⁺ T cells and normal TCRvβ distribution could only be detected in IL-21-treated recipient mice. Astonishingly, none of the recipient mice who underwent IL-21 treatment developed graft-versus-host disease (GVHD) in the MHC-matched allogeneic setting while the graft-versus-tumor (GVT) effect was strongly retained. Inhibition of GVHD onset could also be attributed to the enhanced generation of regulatory B cells (B10) observed in the IL-21, but not PBS, recipient mice. We also tested the thymopoiesis-stimulating property of human IL-21 in NSG mice transplanted with cord blood (CB) and found significant improvement in de novo human CD3⁺ T cell development.

CONCLUSIONS

In sum, our study indicates that IL-21 represents a new class of unforeseen thymopoietin capable of restoring thymic function following BMT.

Transplant of ex vivo incubated bone marrow with rIL -7 for the enhancement of immuno-hematopoietic reconstitution

Interleukin-7 (IL-7) is a critical cytokine in early B and T cell development. Peripheral T cell expansion and thymopoiesis and is a result of the ongoing reconstitution from uncommitted stem cells after transplant. We investigated the efficacy of ex vivo incubated bone marrow cells treated with recombinant human IL-7 (rIL-7) on subsequent in vivo murine models of syngeneic bone marrow (BM) transplant. After ex vivo culture with rIL-7, we observed a 1½-fold increase in BM cellularity; this increase was associated with an enhanced reconstitution of bone marrow cells and thymocytes at 45 days post-transplant. In addition to increased cellularity, lymphocytes from mice transplanted with cultured rIL-7 showed enhanced proliferative responses to mitogenic stimulation. These findings suggest rIL-7 to be a promising agent for the clinical application of treating immune deficiency and enhancing immuno-hematopoietic reconstitution of the stem cell auto/allograft.

Fabrication principles and their contribution to the superior in vivo therapeutic efficacy of nano-liposomes remote loaded with glucocorticoids

We report here the design, development and performance of a novel formulation of liposome- encapsulated glucocorticoids (GCs). A highly efficient (>90%) and stable GC encapsulation was obtained based on a transmembrane calcium acetate gradient driving the active accumulation of an amphipathic weak acid GC pro-drug into the intraliposome aqueous compartment, where it forms a GC-calcium precipitate. We demonstrate fabrication principles that derive from the physicochemical properties of the GC and the liposomal lipids, which play a crucial role in GC release rate and kinetics. These principles allow fabrication of formulations that exhibit either a fast, second-order (t(1/2) ~1 h), or a slow, zero-order release rate (t(1/2) ~ 50 h) kinetics. A high therapeutic efficacy was found in murine models of experimental autoimmune encephalomyelitis (EAE) and hematological malignancies.

Promotional etiology for common childhood acute lymphoblastic leukemia: the infective lymphoid recovery hypothesis

This paper speculates on the role of infection in modifying a young child's risk of promoting precursor B-cell acute lymphoblastic leukemia (ALL). It is suggested that the heat shock instigated by infections, particularly in infancy, stimulates Th1 pro-inflammatory cytokines and an apoptosis-inhibitory environment. This infective stress also increases the number of cooperating oncogenic mutations in pre-leukemic cells, especially if the primary adaptive immune response is delayed. The glucocorticoid release that follows leads to acute thymic involution, a decline in antitumor immunity, and maturation arrest of B-lymphocytes. The infective lymphoid recovery hypothesis addresses an apparent contradiction-that a non-hygienic environment primes the adaptive immune response and is protective against childhood ALL, while multiple infections occurring later increase the risk of childhood ALL. In affluent (compared to less-affluent) societies, the characteristic ALL incidence peak in early childhood, and the shortened time to diagnosis, arise from surviving recurrent infections and the accumulated loss and recovery of lymphoid tissue. Evidence supporting the hypothesis, such as the role of lymphoid tissue reconstitution cytokines that stimulate proliferation stress on B-cell progenitors, comes from the study of children with congenital syndromes that are susceptible to leukemia.

Clinical impact of absolute lymphocyte count on day 30 after unmanipulated haploidentical blood and marrow transplantation for pediatric patients with hematological malignancies

Currently, limited information is available regarding the effects of early lymphocyte recovery on transplant outcomes in pediatric patients with hematological malignancies after unmanipulated haploidentical transplantation. In this study, we evaluated the association of Day 30 absolute lymphocyte count (ALC-30) with transplant outcomes in 60 consecutive pediatric patients with hematological malignancies receiving T-cell-repleted transplantation from an haploidentical related donors. After median follow-up of 36 months (range, 1.4-75 months), higher relapse rate was observed in patients with an ALC-30 < 300 cells/μL compared to patients with an ALC-30 ≥ 300 cells/μL (35.5% vs. 13.8%, P = 0.049). More patients died of infections in those with an ALC-30 < 300 cells/μL compared with patients with an ALC-30 ≥ 300 cells/μL (25.8% vs. 3.4%, P = 0.015). The ALC-30 above the cutoff value 300 cells/μL was associated with improved overall-survival (HR 0.301, 95% CI 0.117-0.771; P = 0.012), leukemia free survival (HR 0.195, 95% CI 0.078-0.498; P=0.002), less relapse (HR 0.224 95% CI 0.070-0.717; P = 0.012), and less transplant- related mortality (HR=0.166; 95%CI 0.037-0.750; P = 0.020). Our results suggest that a higher ALC-30 ≥ 300 cells/μL) could be a useful and simple tool to predict pediatric patients with a superior outcome after unmanipulated haploidentical transplantation.

Chronic myelogenous leukemia maintains specific CD8(+) T cells through IL-7 signaling

Chronic myelogenous leukemia (CML) is a malignant myeloproliferative disease of hematopoietic stem cells. The disease progresses after several years from an initial chronic phase to a blast phase. Leukemia-specific T cells are regularly detected in CML patients and may be involved in the immunological control of the disease. Here, we analyzed the role of leukemia-specific CD8(+) T cells in CML disease control and the mechanism that maintains CD8(+) T-cell immunosurveillance in a retroviral-induced murine CML model. To study antigen-specific immune responses, the glycoprotein of the lymphocytic choriomeningitis virus was used as model leukemia antigen. Leukemia-specific CTL activity was detectable in vivo in CML mice and depletion of CD8(+) T cells rapidly led to disease progression. CML-specific CTL were characterized by the expression of the IL-7 receptor α-chain. In addition, leukemia cells produced IL-7 that was crucial for the maintenance of leukemia-specific CTL and for disease control. Therefore, CML cells maintain the specific CD8(+) T-cell-mediated immune control by IL-7 secretion. This results in prolonged control of disease and probably contributes to the characteristic chronic phase of the disease.

Enhancing adoptive immunotherapy of cancer

IMPORTANCE OF THE FIELD

Conventional therapies, including surgery, chemotherapy and radiotherapy have contributed much to cancer treatment. However, these treatment modalities fail in a large proportion of patients, and there is a great need for effective alternate therapies. Adoptive immunotherapy can be effective against some cancers that have failed all other treatment options, even when disease burdens are massive.

AREAS COVERED IN THIS REVIEW

This review gives a brief introduction of the historical origins of adoptive immunotherapy and then provides details of strategies for increasing the potency of cell transfer. Approaches for enhancing adoptive immunotherapy include: selecting the right type of cell; providing cytokine support; preconditioning patients and tuning the tumor microenvironment. The review also provides insights into the safety, feasibility and costs of this form of therapy.

WHAT THE READER WILL GAIN

This article will give the reader an appreciation of the potential of adoptive immunotherapy, as well as an understanding of some limitations and current approaches for optimizing the effectiveness of this approach.

TAKE HOME MESSAGE

With recent developments in knowledge of the interactions between the immune system and tumors, the field of adoptive immunotherapy is now poised to make dramatic contributions to cancer therapy.

Influence of lymphocyte recovery on outcome of haploidentical transplantation for hematologic malignancies

Unmanipulated human leukocyte antigen (HLA)-mismatched/haploidentical blood and marrow transplantation is an established treatment for patients without HLA-matched related or unrelated donors. However, the prognostic significance of early lymphocyte recovery in this transplant setting is not defined. In this study, we investigated the association of day 30 absolute lymphocyte count (ALC-30) with outcome after unmanipulated HLA-mismatched/haploidentical transplantation. We prospectively analyzed the relationship between ALC-30 and transplant outcomes in 206 patients with hematologic malignancies receiving T-cell-replete transplantation from HLA-mismatched/haploidentical related donors. Multivariate analysis showed that ALC-30 above the cutoff value of 300 cells/microL was associated with improved overall survival (hazard ratio [HR], 0.258; 95% confidence interval [CI], 0.141-0.472; p < 0.0001); improved cancer-free survival (HR, 0.289; 95% CI, 0.166-0.501; p < 0.0001); reduced relapse (HR, 0.370; 95% CI, 0.161-0.853; p = 0.020); and decreased transplant-related mortality (HR, 0.211; 95% CI, 0.097-0.457; p < 0.0001). Our results suggest that the recovery of ALC-30 might have an influence on transplant outcomes following unmanipulated HLA-mismatched/haploidentical transplantation.