A high proportion of donor CD4+ T cells expressing the lymph node-homing chemokine receptor CCR7 increases incidence and severity of acute graft-versus-host disease in patients undergoing allogeneic stem cell transplantation for hematological malignancy

Secondary Lymphoid Organs in Mesenchymal Stromal Cell Therapy: More Than Just a Filter

Mesenchymal stromal cells (MSCs) have demonstrated therapeutic potential in inflammatory models of human disease. However, clinical translation has fallen short of expectations, with many trials failing to meet primary endpoints. Failure to fully understand their mechanisms of action is a key factor contributing to the lack of successful commercialisation. Indeed, it remains unclear how the long-ranging immunomodulatory effects of MSCs can be attributed to their secretome, when MSCs undergo apoptosis in the lung shortly after intravenous infusion. Their apoptotic fate suggests that efficacy is not based solely on their viable properties, but also on the immune response to dying MSCs. The secondary lymphoid organs (SLOs) orchestrate immune responses and play a key role in immune regulation. In this review, we will discuss how apoptotic cells can modify immune responses and highlight the importance of MSC-immune cell interactions in SLOs for therapeutic outcomes.

Peripheral blood stem cell grafts in allogeneic hematopoietic cell transplantation: It is not all about the CD34+ cell dose

Allogeneic Hematopoietic Cell Transplantation is a curative approach in various malignant and non-malignant disorders. The majority of adult transplants in the current era are performed using mobilized stem cells, harvested from the peripheral blood by leukapheresis. Peripheral blood stem cell (PBSC) collections are designed to target a dose of stem cells that will result in safe engraftment and hematopoietic recovery; however, 99 % of the cells contained in a PBSC graft are not stem cells and a growing number of studies attempt to characterize the associations between graft composition and transplant outcomes. A better understanding of the impact of the quantity and quality of various cell types in PBSC grafts may lead to development of novel collection strategies or improved donor selection algorithms. Here we review relevant findings from recent studies in this area.

Evaluation of therapeutic targeting of CCR7 in acute graft-versus-host disease

Graft-versus-host disease (GVHD) is the main complication after allogeneic hematopoietic stem cell transplantation. We previously unveiled a correlation between proportions of C-C motif chemokine receptor 7 (CCR7)⁺ T cells in the apheresis and the risk of developing GVHD. We wanted to evaluate in vivo whether apheresis with low proportion of CCR7⁺ cells or treatment with an anti-human CCR7 monoclonal antibody (mAb) were suitable strategies to prevent or treat acute GVHD in preclinical xenogeneic models. Therapeutic anti-CCR7 mAb was the most effective strategy in both prophylactic and therapeutic settings where antibody drastically reduced in vivo lymphoid organ infiltration of donor CCR7⁺ T cells, extended lifespan and solved clinical signs. The antibody neutralized in vitro migration of naïve and central memory T cells toward CCR7 ligands and depleted target CCR7⁺ subsets through complement activation. Both mechanisms of action spared CCR7^- subsets, including effector memory and effector memory CD45RA⁺ T cells which may mediate graft versus leukemia effect and immunity against infections. Accordingly, the numbers of donor CCR7⁺ T cells in the apheresis were not associated to cytomegalovirus reactivation or the recurrence of the underlying disease. These findings provide a promising new strategy to prevent and treat acute GVHD, a condition where new specific, safety and effective treatment is needed.

R707, a fully human antibody directed against CC-chemokine receptor 7, attenuates xenogeneic acute graft-versus-host disease

Acute graft-versus-host disease (aGVHD) remains a barrier to the success of allogeneic hematopoietic stem cell transplantation (HSCT). Previously, we demonstrated that CC-chemokine receptor 7 (CCR7) is critical for aGVHD pathogenesis but dispensable for beneficial graft-versus-leukemia responses. As a result, we evaluated a fully human anti-CCR7-blocking antibody as a new approach to prevent aGVHD in preclinical models. Here we report that antibody R707 is able to block human CCR7 signaling and function in vitro in response to its 2 natural ligands. The antibody was less active against the murine orthologue, however, and failed to substantially limit aGVHD in a standard murine allogeneic HSCT model. Nevertheless, R707 significantly reduced xenogeneic aGVHD induced by human peripheral blood mononuclear cells (PBMCs). R707 limited CD4⁺ and in particular CD8⁺ T cell expansion during the period of antibody administration. These effects were transient, however, and T cell numbers recovered after antibody cessation. R707 did not substantially impair the antitumor potential of the PBMC inoculum as antibody-treated mice retained their capacity to reject a human acute myeloid leukemia cell line. Collectively, these data indicate for the first time that an antibody directed against CCR7 might represent a viable new approach for aGVHD prevention.

Expanding Therapeutic Opportunities for Hematopoietic Stem Cell Transplantation: T Cell Depletion as a Model for the Targeted Allograft

Allogeneic hematopoietic cell transplantation is a fundamental part of the treatment of hematologic malignancies and marrow failure syndromes, but complications including graft-versus-host disease, prolonged immune deficiency and infection, and organ toxicities, as well as relapse, remain obstacles to improved overall survival. As the cellular characteristics of the allograft can exert significant impact on outcomes, the development of more strategically designed grafts represents a rich area for therapeutic intervention. We describe the use of ex vivo T cell–depleted grafts as a model for the targeted graft and review evolving knowledge and approaches for further refinement of allografts to improve patient outcomes.

The Ex Vivo Treatment of Donor T Cells with Cosalane, an HIV Therapeutic and Small-Molecule Antagonist of CC-Chemokine Receptor 7, Separates Acute Graft-versus-Host Disease from Graft-versus-Leukemia Responses in Murine Hematopoietic Stem Cell Transplantation Models

Despite recent advances in therapy, allogeneic hematopoietic stem cell transplantation (HSCT) remains the only curative option for a range of high-risk hematologic malignancies. However, acute graft-versus-host disease (aGVHD) continues to limit the long-term success of HSCT, and new therapies are still needed. We previously demonstrated that aGVHD depends on the ability of donor conventional T cells (T_cons) to express the lymph node trafficking receptor, CC-Chemokine Receptor 7 (CCR7). Consequently, we examined the ability of cosalane, a recently identified CCR7 small-molecule antagonist, to attenuate aGVHD in mouse HSCT model systems. Here we show that the systemic administration of cosalane to transplant recipients after allogeneic HSCT did not prevent aGVHD. However, we were able to significantly reduce aGVHD by briefly incubating donor T_cons with cosalane ex vivo before transplantation. Cosalane did not result in T_con toxicity and did not affect their activation or expansion. Instead, cosalane prevented donor T_con trafficking into host secondary lymphoid tissues very early after transplantation and limited their subsequent accumulation within the liver and colon. Cosalane did not appear to impair the intrinsic ability of donor T_cons to produce inflammatory cytokines. Furthermore, cosalane-treated T_cons retained their graft-versus-leukemia (GVL) potential and rejected a murine P815 inoculum after transplantation. Collectively, our data indicate that a brief application of cosalane to donor T_cons before HSCT significantly reduces aGVHD in relevant preclinical models while generally sparing beneficial GVL effects, and that cosalane might represent a viable new approach for aGVHD prophylaxis.

Successful treatment with fingolimod of graft-versus-host disease of the central nervous system

Fingolimod could be efficient to treat GVHD of the central nervous system.Further research should explore the use of fingolimod and other sphingosine-1-phosphate receptor agonists to prevent or treat GVHD.

CXCR3 blockade combined with cyclosporine A alleviates acute graft-versus-host disease by inhibiting alloreactive donor T cell responses in a murine model

Chemotaxis of T cells to acute graft-versus-host disease (aGvHD) target tissues directed by chemokines and their receptors plays a key role in the pathogenesis of aGvHD. Blockade of lymphocyte migration by targeting chemokine receptors may be a viable strategy for the prevention and treatment of aGvHD, which is quite distinguishable from typical efforts to use immunosuppressive medications that have been associated with some side effects. CXCR3 and its ligands have been reported to be correlated with aGvHD pathogenesis. Using the small-molecule CXCR3 antagonist AMG487, we demonstrated that AMG487 combined with cyclosporine A (CsA) effectively alleviated aGvHD with a prolonged mean survival time and significantly inhibited the infiltration of inflammatory cells in aGvHD target tissues in a murine aGvHD model. In addition, AMG487 combined with CsA inhibited the activation, proliferation and differentiation of donor-derived T cells in the spleens. Further results showed that the concentrations of Th1 cells associated with pro-inflammatory cytokines such as IFN-γ and TNFα in serum were decreased. In addition, AMG487 treatment did not alter CXCR3 and CCR5 expression in donor-derived T cells but elevated the serum CXCL9 and CXCL10 levels. This novel and effective approach has the potential to develop a new clinical method to prevent and treat aGvHD.

Sequential monitoring of lymphocyte subsets and of T-and-B cell neogenesis indexes to identify time-varying immunologic profiles in relation to graft-versus-host disease and relapse after allogeneic stem cell transplantation

T and B lymphocyte subsets have been not univocally associated to Graft-versus-host disease (GVHD) and relapse of hematological malignancies after stem cell transplantation (SCT). Their sequential assessment together with B and T cell neogenesis indexes has been not thoroughly analysed in relation to these changing and interrelated immunologic/clinic events yet.

Lymphocyte subsets in peripheral blood (PB) and B and T cell neogenesis indexes were analysed together at different time points in a prospective study of 50 patients. Principal component analysis (PCA) was used as first step of multivariate analysis to address issues related to a high number of variables versus a relatively low number of patients. Multivariate analysis was completed by Fine-Gray proportional hazard regression model. PCA identified 3 clusters of variables (PC1-3), which correlated with acute GVHD: PC1 (pre-SCT: KRECs≥6608/ml, unswitched memory B <2.4%, CD4+T_CM cells <45%; HR 0.5, p = 0.001); PC2 (at aGVHD onset: CD4+>44%, CD8+T_CM cells>4%; HR 1.9, p = 0.01), and PC3 (at aGVHD onset: CD4+TEM_RA<1, total Treg<4, Treg_EM <2 cells/μl; HR 0.5, p = 0.002). Chronic GVHD was associated with one PC (Treg_EM <2 cells/μl at day+28, CD8+TEM_RA<43% at day+90, immature B cells<6 cells/μl and KRECs<11710/ml at day+180; HR 0.4, P = 0.001). Two PC correlated with relapse: PC1 (pre-SCT: CD4+ <269, CD4+T_CM <120, total Treg <18, Treg_CM <8 cells/μl; HR 4.0, p = 0.02); PC2 (pre-SCT mature CD19+ >69%, switched memory CD19+ = 0 cells and KRECs<6614/ml at +90; HR 0.1, p = 0.008). All these immunologic parameters were independent indicators of chronic GVHD and relapse, also considering the possible effect of previous steroid-therapy for acute GVHD. Specific time-varying immunologic profiles were associated to GVHD and relapse. Pre-SCT host immune-microenvironment and changes of B cell homeostasis could influence GVH- and Graft-versus-Tumor reactions. The paradoxical increase of EM Treg in PB of patients with GVHD could be explained by their compartmentalization outside lymphoid tissues, which are of critical relevance for regulation of GVH reactions.

A high migratory capacity of donor T-cells in response to the lymph node homing receptor CCR7 increases the incidence and severity of GvHD

The pathogenesis of GvHD involves migration of donor T-cells into the secondary lymphoid organs in the recipient, which is steered by two homing molecules, CD62L and CCR7. Therefore, we investigated whether the migratory capacity of donor T-cells is associated with GvHD. This single center prospective study included 85 donor-recipient pairs. In vitro chemotaxis assays of the lymphocytes of the apheresis product were performed in parallel to the analysis of CD62L and CCR7 by flow cytometry. The migratory index to the CCR7 ligands, CCL19 and CCL21, was higher in T-cells from donors whose recipients will develop GvHD. Similarly, the acute GvHD (aGvHD) group received higher percentage of CD4+CCR7+ T-cells, whereas chronic GvHD (cGvHD) patients were transplanted with higher percentages of CD8+CCR7+ T-cells compared with the non-GvHD group. These results were confirmed when patients were subdivided according to degrees of severity. Further, multivariate analysis confirmed that the proportions of CCR7+ CD4+ and CCR7+ CD8+ T-cells are risk factors for the development and severity of aGvHD and cGvHD, respectively. Functional experiments demonstrated that CCR7+ T-cells exhibited higher potential for activation than CCR7- T-cells did. We therefore propose that the selective depletion of CCR7-expressing T-cells may be an effective preventive therapy for GvHD.

Pre-transplant donor CD4- invariant NKT cell expansion capacity predicts the occurrence of acute graft-versus-host disease

Clinically useful pre-transplant predictive factors of acute graft-versus-host-disease (aGVHD) after allogeneic hematopoietic stem cell transplantation (allo-SCT) are lacking. We prospectively analyzed HSC graft content in CD34⁺, NK, conventional T, regulatory T and invariant natural killer T (iNKT) cells in 117 adult patients before allo-SCT. Results were correlated with occurrence of aGVHD and relapse. In univariate analysis, iNKT cells were the only graft cell populations associated with occurrence of aGVHD. In multivariate analysis, CD4^- iNKT/T cell frequency could predict grade II-IV aGVHD in bone marrow and peripheral blood stem cell (PBSC) grafts, while CD4^- iNKT expansion capacity was predictive in PBSC grafts. Receiver operating characteristic analyses determined the CD4^- iNKT expansion factor as the best predictive factor of aGVHD. Incidence of grade II-IV aGVHD was reduced in patients receiving a graft with an expansion factor above versus below 6.83 (9.7 vs 80%, P<0.0001), while relapse incidence at two years was similar (P=0.5).The test reached 94% sensitivity and 100% specificity in the subgroup of patients transplanted with human leukocyte antigen 10/10 PBSCs without active disease. Analysis of this CD4^- iNKT expansion capacity test may represent the first diagnostic tool allowing selection of the best donor to avoid severe aGVHD with preserved graft-versus-leukemia effect after peripheral blood allo-SCT.

In vivo engineering of mobilized stem cell grafts with the immunomodulatory drug FTY720 for allogeneic transplantation

The immunological attributes of stem cell grafts play an important role in the outcome of allogeneic stem cell transplants. Currently, ex vivo manipulation techniques such as bulk T-cell depletion or positive selection of CD34(+) cells are utilized to improve the immunological attributes of grafts and minimize the potential for graft-versus-host disease (GvHD). Here, we demonstrate a novel graft engineering technique, which utilizes the immunomodulatory drug FTY720 for in vivo depletion of naïve T (TN ) cells from donor G-CSF-mobilized grafts without ex vivo manipulation. We show that treatment of donor mice with FTY720 during mobilization depletes grafts of TN cells and prevents lethal GvHD following transplantation in a major mismatch setting. Importantly, both stem cells and NK cells are retained in the FTY720-treated grafts. FTY720 treatment does not negatively affect the engraftment potential of stem cells as demonstrated in our congenic transplants or the functionality of NK cells. In addition, potentially useful memory T cells may be retained in the graft. These findings suggest that FTY720 may be used to optimize the immunological attributes of G-CSF-mobilized grafts by removing potentially deleterious TN cells which can contribute to GvHD, and by retaining useful cells which can promote immunity in the recipient.

Impact of Pre-Transplant Anti-T Cell Globulin (ATG) on Immune Recovery after Myeloablative Allogeneic Peripheral Blood Stem Cell Transplantation

Background

Pre-transplant infusion of rabbit anti-T cell globulin (ATG) is increasingly used as prevention of graft-versus-host disease (GVHD) after allogeneic peripheral blood stem cell transplantation (PBSCT). However, the precise impact of pre-transplant ATG on immune recovery after PBSCT is still poorly documented.

Methods

In the current study, we compared immune recovery after myeloablative PBSCT in 65 patients who either received (n = 37) or did not (n = 28) pre-transplant ATG-Fresenius (ATG-F). Detailed phenotypes of circulating T, B, natural killer (NK) and invariant NKT (iNKT) cells were analyzed by multicolor flow cytometry at serial time-points from day 40 to day 365 after transplantation. Thymic function was also assessed by sjTREC quantification. Serious infectious events were collected up to 2 years post-transplantation.

Results

Pre-transplant ATG-F had a prolonged (for at least up to 1-year) and selective negative impact on the T-cell pool, while it did not impair the recovery of B, NK nor iNKT cells. Among T cells, ATG-F selectively compromised the recovery of naïve CD4⁺, central memory CD4⁺ and naïve CD8⁺ cells, while it spared effector memory T and regulatory T cells. Levels of sjTRECs were similar in both cohorts at 1-year after PBSCT, suggesting that ATG-F unlikely impaired thymopoiesis at long-term after PBSCT. Finally, the incidence and rate of serious infections were similar in both groups, while ATG-F patients had a lower incidence of grade II-IV acute graft-versus-host disease.

Conclusions

Pre-transplant ATG-F induces long-lasting modulation of the circulating T-cell pool after myeloablative PBSCT, that may participate in preventing graft-versus-host disease without deeply compromising anti-pathogen defenses.

Acute graft-versus-host disease: a bench-to-bedside update

Over the past 5 years, many novel approaches to early diagnosis, prevention, and treatment of acute graft-versus-host disease (aGVHD) have been translated from the bench to the bedside. In this review, we highlight recent discoveries in the context of current aGVHD care. The most significant innovations that have already reached the clinic are prophylaxis strategies based upon a refinement of our understanding of key sensors, effectors, suppressors of the immune alloreactive response, and the resultant tissue damage from the aGVHD inflammatory cascade. In the near future, aGVHD prevention and treatment will likely involve multiple modalities, including small molecules regulating immunologic checkpoints, enhancement of suppressor cytokines and cellular subsets, modulation of the microbiota, graft manipulation, and other donor-based prophylaxis strategies. Despite long-term efforts, major challenges in treatment of established aGVHD still remain. Resolution of inflammation and facilitation of rapid immune reconstitution in those with only a limited response to corticosteroids is a research arena that remains rife with opportunity and urgent clinical need.

Donor-derived CD4(+)/CCR7(+) T-cell partial selective depletion does not alter acquired anti-infective immunity

In previous studies, we observed that a high proportion of donor-derived CD4(+) T cells expressing the chemokine receptor 7 (CCR7) was a major determinant of acute GVHD, without interfering with the incidence of other post-transplant outcomes, especially relapse and nonrelapse mortality rates. Here, we investigated in vitro the impact of partially selective CD4(+)/CCR7(+) T lymphocytes on acquired anti-infective immune response in 10 donors who underwent G-CSF-primed PBSC collection. Similar quantitative and functional proliferative reactions were observed in lymphocyte cultures in the presence of adenovirus and pp65 Ags with unmanipulated and partially depleted donor samples. No responses were observed in the presence of human T-cell lymphotropic virus type 1 used as a negative control. These results complete the proof of concept needed to build a clinical trial investigating partially selective CD4(+)/CCR7(+) T cell-depleted allo-SCT.

Immune cell subset counts associated with graft-versus-host disease

Graft-versus-host disease (GVHD) is a major transplantation complication. The purpose of this study was to measure immune cell subsets by flow cytometry early after transplantation (before median day of GVHD onset) to identify subsets that may play a role in GVHD pathogenesis. We also measured the subsets later after transplantation to determine which subsets may be influenced by GVHD or its treatment. We studied 219 patients. We found that acute GVHD (aGVHD) was preceded by high counts of CD4 T cells and CD8 T cells. It was followed by low counts of total and naive B cells, total and cytolytic NK cells, and myeloid and plasmacytoid dendritic cells. Chronic GVHD (cGVHD) was preceded by low counts of memory B cells. In conclusion, both CD4 and CD8 T cells appear to play a role in the pathogenesis of aGVHD. Generation of B cells, NK cells, and dendritic cells may be hampered by aGVHD and/or its treatment. Memory B cells may inhibit the development of cGVHD.

The role of chemokines in mediating graft versus host disease: opportunities for novel therapeutics

Bone marrow transplantation (BMT) is the current therapy of choice for several malignancies and severe autoimmune diseases. Graft versus host disease (GVHD) is the major complication associated with BMT. T lymphocytes and other leukocytes migrate into target organs during GVHD, become activated and mediate tissue damage. Chemokines are well known inducers of leukocyte trafficking and activation and contribute to the pathogenesis of GVHD. Here, we review the major animal models used to study GVHD and the role of chemokines in mediating tissue damage in these models. The role of these molecules in promoting potential beneficial effects of the graft, especially graft versus leukemia, is also discussed. Finally, the various pharmacological strategies to block the chemokine system or downstream signaling events in the context of GVHD are discussed.

Plasma levels of IL-7 and IL-15 after reduced intensity conditioned allo-SCT and relationship to acute GVHD

To assess the impact of homeostatic expansion on the occurrence of acute GVHD after reduced intensity conditioning (RIC) transplantation, systemic levels of IL-7 and IL-15 and expression of their specific receptor chains were prospectively investigated in 45 fully HLA-matched allograft recipients. IL-7 and IL-15 levels peaked at four- to fivefold over pre-conditioning values. IL-7 levels were inversely correlated to absolute T-cell counts. Peak IL-15 levels positively correlated to concurrent CRP levels, but normalized earlier than IL-7. These results indicate that the kinetic course of IL-7 depends mainly on initiation of T-cell recovery, while IL-15 depends more on peri-transplant inflammation after RIC. Longer duration of the rise in IL-7 levels was associated with preservation of a normal CD4/CD8 ratio. In all, 16 (35%) patients developed grade 2-4 acute GVHD at a median of 42 days post graft, preceded by higher IL-7 levels and more downregulation of IL-7 receptor α chain on CD4(+) T cells than in patients without acute GVHD, suggesting enhanced homeostatic expansion. In multivariate analysis, IL-7 level measured on day +30 was the foremost predictive factor for grade 2-4 acute GVHD (P=0.002). Measurement of IL-7 level after RIC transplantation might help predict risk of subsequent acute GvHD.

Plasma levels of IL-7 and IL-15 in the first month after myeloablative BMT are predictive biomarkers of both acute GVHD and relapse

T-cell reconstitution after allo-SCT initially depends on homeostatic peripheral expansion of donor T cells, the level of which may promote the differentiation of alloreactive and tumor-reactive effectors. IL-7 and IL-15 exert their effect as key homeostatic cytokines. We prospectively investigated plasma levels of IL-7 and IL-15 in a homogeneous group of 40 patients in CR of their hematologic malignancy undergoing myeloablative, fully (10/10) HLA-matched BMT. IL-7 and IL-15 proceeded along similar kinetic courses, peaking at wide ranges (3.8-30.2 and 14.3-66 pg/ml, respectively) on day +14 when all patients were profoundly lymphopenic. Occurrence and grade of subsequent acute GVHD were significantly associated with heightened day +14 IL-7 and IL-15 levels. Association of peak IL-7 level to grade 2-4 acute GVHD was confirmed by Cox multivariate analysis (hazard ratio (HR)=5.38; P=0.022). Malignancy relapse was significantly associated with reduced day +14 levels of IL-15 (Cox multivariate analysis: HR=0.93; P=0.035). Plasma IL-7 and IL-15 levels in the early post transplantation period are therefore biomarkers that can help predict subsequent development of acute GVHD and malignancy relapse.

Acute graft-versus-host disease: new treatment strategies

PURPOSE OF REVIEW

Graft-versus-host disease (GVHD) remains a major cause of morbidity and mortality after allogeneic hematopoietic cell transplantation (HCT), despite improvements in our understanding of its pathophysiology as well as the generation of new monoclonal antibodies, immunomodulatory chemotherapy, cellular therapeutics and supportive care. Herein, we review therapies that have proven effective as well as newer agents that have recently improved GVHD response rates and survival following HCT.

RECENT FINDINGS

Novel approaches to prevent or treat GVHD are often based on evidence from experimental models. Our understanding of the pathophysiology of GVHD may lead to the development of innovative strategies that target both soluble and cellular effectors. Among such agents are sirolimus, anti-tumor necrosis factor antibodies, anti-LFA-3-IgG fusion protein, extracorporeal photopheresis, mesenchymal stem cells and regulatory T cells.

SUMMARY

Obstacles to the improvement of HCT include the tight linkage between GVHD toxicity and the beneficial graft-versus-leukemia (GVL) effect, as well as the impairment of immune reconstitution by immunomodulatory drugs leading to life-threatening infections. The design of newer phase I/II clinical trials are underway. Future therapies are likely to include modulation of cell types that play key roles in the GVH process, including regulatory T cells, dendritic cells, natural killer T cells and B cells.

The chemokine system: a possible therapeutic target in acute graft versus host disease

Allogeneic hematopoetic stem cell transplantation often presents the only chance for cure in a number of malignant and nonmalignant hematologic diseases. However, its beneficial effects are counterweighed by the development of potentially lethal complications, most importantly the development of acute and chronic graft-vs.-host disease (GVHD). Alloantigen-reactive immune responses mediate injury and destruction of GVHD target organs, including the gastrointestinal tract, the liver, the skin, and the lung. Donor leukocyte infiltration into the respective tissues is orchestrated by interactions between chemokines and chemokine receptors, which will be reviewed using a basic science - clinical comparative approach.

Up-Regulation of alpha4beta7 integrin on peripheral T cell subsets correlates with the development of acute intestinal graft-versus-host disease following allogeneic stem cell transplantation

Acute graft-versus-host disease (aGVHD) is a major complication after hematopoietic stem cell transplantation (HSCT). The pathophysiology of aGVHD involves priming of naïve donor T cells in host secondary lymphoid tissue, followed by migration of effector T cells to target organs. Mediators of lymphocyte trafficking are believed to play a significant role in this migration. In this retrospective case-controlled study, we analyzed the expression of alpha4beta7 integrin and CCR9, 2 surface T cell molecules specific for intestinal trafficking, from blood samples collected previously from 59 patients after HSCT (20 without aGVHD, 20 with skin aGVHD, and 19 with intestinal aGVHD). All samples had been obtained before the onset of aGVHD symptoms (with 1 sample collected on the day of symptom onset). Analysis by flow cytometry demonstrated that alpha4beta7 integrin was significantly increased on both naïve and memory T cells in patients who subsequently developed intestinal aGVHD, with the most significant differences observed in memory subsets. Immunohistochemical staining on rectal biopsy specimens from patients with intestinal aGVHD showed that expression of alpha4beta7 integrin was concentrated on mononuclear cells in blood vessels within the intestinal mucosa. These results suggest that alpha4beta7 integrin likely is involved in lymphocyte trafficking in intestinal aGVHD and may have potential clinical use as a correlative biomarker or as a target for the treatment and prophylaxis of intestinal aGVHD after HSCT.

Imbalance of effector and regulatory CD4 T cells is associated with graft-versus-host disease after hematopoietic stem cell transplantation using a reduced intensity conditioning regimen and alemtuzumab

BACKGROUND

A variety of immune pathways can lead to graft-versus-host disease. A better understanding of the type of immune response causing graft-versus-host disease in defined clinical hematopoietic stem cell transplant settings is required to inform development of methods for monitoring patients and providing them tailored care.

DESIGN AND METHODS

Twenty-five patients were recruited presenting with myeloid malignancies and treated with a reduced intensity conditioning transplant regimen with graft-versus-host disease prophylaxis comprising in vivo lymphocyte depletion with alemtuzumab and cyclosporin. A prospective study was performed of lymphocyte subset reconstitution in peripheral blood in relation to the incidence of graft-versus-host disease.

RESULTS

Acute graft-versus-host disease was associated with significantly higher numbers of natural killer cells and donor-derived effector CD4 T cells (CD45RO(+) CD27(-)) early (day 30) after transplantation (p=0.04 and p=0.02, respectively). This association was evident before the emergence of clinical pathology in six out of seven patients. Although numbers of regulatory CD4 T cells (CD25(high) Foxp3(+)) were similar at day 30 in all patients, a significant deficit in those who developed acute graft-versus-host disease was apparent relative to effector CD4 T cells (median of 41 effectors per regulatory cell compared to 12 to 1 for patients without graft-versus-host disease) (p=0.03). By day 180, a functional regulatory CD4 T-cell population had expanded significantly in patients who developed chronic graft-versus-host disease, reversing the imbalance (median of 3 effectors per regulatory cell compared to 9.6 to 1 for patients without graft-versus-host disease) (p=0.018) suggesting no overt absence of immune regulation in the late onset form of the disease.

CONCLUSIONS

Imbalance of effector and regulatory CD4 T cells is a signature of graft-versus-host disease in this transplantation protocol.

G-CSF induces a potentially tolerant gene and immunophenotype profile in T cells in vivo

G-CSF can induce functional immune tolerance in man. In this study, purified T cells from G-CSF-mobilized peripheral blood stem cell (PBSC) donors were analysed by gene expression profiling and immunophenotyping. Results suggested a predominantly immune tolerant profile with upregulation of genes related to Th2 and Treg cells, downregulation of genes associated with Th1 cells, cytotoxicity, antigen presentation and graft-versus-host disease (GVHD) and overexpression of negative regulators of Th17 differentiation. Immunophenotyping revealed that during G-CSF exposure donors had reduced levels of T cells with a Th17 phenotype (CD4+IL-17A+CCR6+IL-23R+), more than three times lower compared to normal controls. G-CSF also led to increased levels of CD4+CD25highCD45RO+ Treg cells. Furthermore, mRNA levels of RORgammat, a Th17-specific transcription factor, decreased in T cells isolated from G-CSF-mobilized PBSC harvests. Th17 cells have been implicated in autoimmune diseases and GVHD pathophysiology. Our study is the first to report the effect of G-CSF on the Th17 subpopulation.

Alloreactivity of ex vivo-expanded T cells is correlated with expansion and CD4/CD8 ratio

Background We have demonstrated previously that retroviral-mediated transfer of a suicide gene into bone marrow (BM) donor T cells allows an efficient control of graft-versus-host disease (GvHD) after allogeneic BM transplantation. However, the 12 days of ex vivo culture required for the production of gene-modified cells (GMC), including soluble CD3 monoclonal antibody (MAb)-mediated activation and expansion with interleukin (IL)-2, induced a decrease of GMC alloreactivity and a reversal of their CD4/CD8 ratio. Improving the culture protocol in order to maintain the highest alloreactivity is of critical importance in obtaining an optimal graft-versus-leukemia (GvL) effect. Methods Peripheral blood mononuclear cells were activated with soluble CD3 MAb or CD3 and CD28 MAb co-immobilized on beads and expanded for 12 days in the presence of IL-2, IL-7 or IL-15 before analysis of alloreactivity and phenotype. Results Replacing the CD3 MAb by CD3/CD28 beads led to similar in vitro alloreactivity but improved the expansion and in vivo alloreactivity of GMC. Replacing the IL-2 with IL-7, but not IL-15, or decreasing IL-2 or IL-7 concentrations, improved the in vitro alloreactivity of expanded cells but was associated with lower expansion. Indeed, the alloreactivity of expanded cells was negatively correlated with cell expansion and positively correlated with CD4/CD8 ratio and CD8 expression level. Discussion Quantitative (i.e. low CD4/CD8 ratio) and qualitative (e.g. low CD8 expression) defects may account for the decreased alloreactivity of GMC. Using CD3/CD28 beads and/or IL-7 is more beneficial than CD3 MAb and IL-2 for preventing perturbations of the alloreactivity and phenotype of GMC.

Comparative analysis of naïve and memory CD4+ and CD8+ T-cell subsets in bone marrow and G-CSF-mobilized peripheral blood stem cell allografts: impact of donor characteristics

OBJECTIVE

Donor T cells expressing lymph node homing receptors are the foremost initiators of acute graft-vs-host disease (aGVHD), and a high proportion of CD4(+)CCR7(+) T cells in human leukocyte antigen-matched allografts has been shown to confer a high risk of aGVHD without interfering in other outcomes.

METHODS

Naïve, central memory (T(CM)), effector memory (T(EM)), and terminally differentiated effector memory (T(TD)) subsets, further subdivided by CD28 expression, were compared in 52 bone marrow and 37 granulocyte colony-stimulating factor-mobilized peripheral blood harvests.

RESULTS

CCR7(+) cells (naïve and T(CM)) predominated in the CD4(+) population, whereas CD8(+) memory cells were chiefly CCR7(neg) in the grafts. Donor age, antecedent of chronic infections, and graft type were independent factors influencing graft composition. CD8(+) naïve cells negatively correlated and CD8(+) T(EM) positively correlated with age. Cytomegalovirus seropositivity was associated with more CD8(+) T(TD) and diminished CD28 expression. Toxoplasmosis seropositivity was associated with more CD4(+) T(CM) (p = 0.021). Marrow grafts comprised more CD28(+) cells within CD8(+) T(TD), but the percentage of CD4(+)CCR7(+) cells did not differ significantly between the two graft sources. Each of the four CD4(+) subsets and the percentage of CD4(+)CCR7(+) cells (p < 0.001) were correlated between graft and venous blood analyzed in 42 donors before harvest procedures.

CONCLUSION

This study provides reference values for CD4(+) and CD8(+) naïve and memory subsets within allografts applicable to the healthy donor population and indicates that beforehand analysis of a whole-blood sample can help evaluating the risk of aGVHD conferred by each donor and, when possible, choosing the one conferring the lowest risk.