Invasive Fungal Infection in Haematopoietic Stem Cell Transplant Recipients: Epidemiology from the Transplant Physician’s Viewpoint

The practice of hematopoietic stem cell transplantation (HSCT) has undergone many changes that affect the likelihood that a given patient would develop an invasive fungal infection (IFI). The risks for IFI and the types of IFI that may occur are not continuous over the time course after transplantation. IFIs vary with the events that occur during the pre-engraftment neutropenic period, the early post-engraftment period until approximately day 100 post-transplant, and those in the late post-engraftment period after day 100. A number of well-recognized transplant recipient-, transplant procedure-, and transplant complication-related factors play a role in the likelihood of IFI. Important recipient-related factors include age, state of the underlying disease for which the HSCT is being done, and treatment-related history. Transplant procedure-related factors include the type of transplant (autologous or allogeneic), the use of and timing of anti-fungal prevention strategies including whether or not the transplant was conducted in a protected environment to minimize environmental exposure to mould conidia, the choice of conditioning (myeloablative or non-myeloablative), human leucocyte antigen-relatedness [autologous, matched related, mismatched related (including haploidentical pairings), unrelated (matched or mismatched)], stem cell source (bone marrow, peripheral, or cord blood), stem cell dosing, and stem cell product processing (red cell, plasma, or T-lymphocyte depletions, or CD34 selections). Transplant-related complications include duration of pre-engraftment period of neutropenia, graft failure or rejection, the degree of cytotoxic conditioning therapy-related intestinal mucosal damage, acute and chronic graft-versus-host disease (GvHD), the use of corticosteroids for the prevention or management of GvHD, the presence of cytomegalovirus infection and disease. The interaction of these factors over a given patient’s journey through HSCT conspires to promote or reduce the overall IFI risk and set the conditions for the development of any given IFI. The following discussion attempts to look at this from the perspective of the transplant physician struggling to account for these interactions and their attendant risks for IFI.     

Shift of graft-versus-host-disease target organ tropism by dietary vitamin A

Gut-homing of donor T cells is causative for the development of intestinal GvHD in recipients of allogeneic hematopoietic stem cell transplantation (HSCT). Expression of the gut-specific homing receptors integrin-α4β7 and chemokine receptor CCR9 on T cells is imprinted in gut-associated lymphoid tissues (GALT) under the influence of the vitamin A metabolite retinoic acid. Here we addressed the role of vitamin A deficiency in HSCT-recipients for donor T cell migration in the course of experimental GvHD. Vitamin A-deficient (VAD) mice were prepared by feeding them a vitamin A-depleted diet. Experiments were performed in a C57BL/6 into BALB/c model of acute GvHD. We found that expression of integrin-α4β7 and CCR9 in GALT was reduced in VAD recipients after HSCT. Competitive in vivo homing assays showed that allogeneic T cells primed in VAD mice did not home as efficiently to the intestine as T cells primed in mice fed with standard diet (STD). The course of GvHD was ameliorated in VAD HSCT-recipients and, consequently, their survival was prolonged compared to recipients receiving STD. However, VAD-recipients were not protected and died of clinical GvHD. We found reduced numbers of donor T cells in the intestine but increased cell counts and tissue damage in other organs of VAD-recipients. Furthermore, we observed high IFN-γ(+)CD4(+) and low FoxP3(+)CD4(+) frequencies of total donor CD4(+) T cells in VAD as compared to STD recipients. Taken together, these results indicate that dietary vitamin A deficiency in HSCT-recipients changed target organ tropism in GvHD but also resulted in fatal inflammation after HSCT.     

Improving immune reconstitution while preventing GvHD in allogeneic stem cell transplantation

Allogeneic hematopoietic stem cell transplantation (HSCT) is the treatment of choice for many hematologic malignancies and inherited disorders of the hematopoietic system. Ex vivo T-cell depletion (TCD) of the graft and post-transplantation immunosuppression efficiently prevents the development of GvHD in no- MHC-identical settings. However, the consequence of these non-specific strategies is a long-lasting immunodeficiency associated with increased incidence of disease relapse, graft rejection and reactivation of viral infections. Donor lymphocyte infusion, which is used for treating leukemic relapse after allogeneic HSCT, can result in severe GvHD. Several strategies are being optimized specifically to inactivate anti-host T cells while preserving anti-leukemic or anti-microbial immunocompetence. Based on the ex vivo or in vivo elimination of anti-host T cells, or on the modulation of their anti-host activity, these approaches, which have been explored extensively in pre-clinical studies and tested in some preliminary clinical trials, are discussed in this paper.     

Mouse models of graft-versus-host disease: advances and limitations

The limiting factor for successful hematopoietic stem cell transplantation (HSCT) is graft-versus-host disease (GvHD), a post-transplant disorder that results from immune-mediated attack of recipient tissue by donor T cells contained in the transplant. Mouse models of GvHD have provided important insights into the pathophysiology of this disease, which have helped to improve the success rate of HSCT in humans. The kinetics with which GvHD develops distinguishes acute from chronic GvHD, and it is clear from studies of mouse models of GvHD (and studies of human HSCT) that the pathophysiology of these two forms is also distinct. Mouse models also further the basic understanding of the immunological responses involved in GvHD pathology, such as antigen recognition and presentation, the involvement of the thymus and immune reconstitution after transplantation. In this Perspective, we provide an overview of currently available mouse models of acute and chronic GvHD, highlighting their benefits and limitations, and discuss research and clinical opportunities for the future.     

Dysfunction of Bone Marrow Vascular Niche in Acute Graft-Versus-Host Disease after MHC-Haploidentical Bone Marrow Transplantation

Acute graft-versus-host disease (aGvHD) is the most common complication of allogeneic hematopoietic stem cell transplantation (HSCT), which is often accompanied by impaired hematopoietic reconstitution. Sinusoidal endothelial cells (SECs) constitute bone marrow (BM) vascular niche that plays an important role in supporting self-renewal capacity and maintaining the stability of HSC pool. Here we provide evidences that vascular niche is a target of aGvHD in a major histocompatibility complex (MHC)–haploidentical matched murine HSCT model. The results demonstrated that hematopoietic cells derived from GvHD mice had the capacity to reconstitute hematopoiesis in healthy recipient mice. However, hematopoietic cells from healthy donor mice failed to reconstitute hematopoiesis in GvHD recipient mice, indicating that the BM niche was impaired by aGvHD in this model. We further demonstrated that SECs were markedly reduced in the BM of aGvHD mice. High level of Fas and caspase-3 expression and high rate of apoptosis were identified in SECs, indicating that SECs were destroyed by aGvHD in this murine HSCT model. Furthermore, high Fas ligand expression on engrafted donor CD4⁺, but not CD8⁺ T cells, and high level MHC-II but not MHC-I expression on SECs, suggested that SECs apoptosis was mediated by CD4⁺ donor T cells through the Fas/FasL pathway.     

异基因造血干细胞移植后并发自身免疫性溶血性贫血的治疗进展

异基因造血干细胞移植（HSCT）后自身免疫性溶血性贫血（AIHA）是HSCT后并不少见的并发症,其发病率约1﹪~ 6﹪,不同于一般的AIHA,HSCT后AIHA发病机制尚未完全明确,可能与HSCT后受者体内免疫失调相关。危险因素与移植患者年龄小、非恶性疾病、使用无关供者、半相合供者移植、脐血移植、去T细胞移植及移植后并发慢性移植物抗宿主病（GVHD）等有关。皮质激素作为一线治疗,疗效有限,难以持续缓解,需联合使用利妥昔单抗（RTX）、大剂量丙种球蛋白等,甚至需要联合霉酚酸酯、环磷酰胺、西罗莫司、阿伦单抗、依库丽单抗或蛋白酶体抑制剂硼替佐米等免疫抑制剂治疗,部分患者需行血浆置换,偶有行脾切除术者。移植后AIHA总死亡率常高达50﹪,总体预后差于单纯AIHA。该综述旨在总结HSCT后并发AIHA的最新治疗进展,供临床医师参考。     

Monitoring of human cytomegalovirus and virus-specific T-cell response in young patients receiving allogeneic hematopoietic stem cell transplantation

In allogeneic hematopoietic stem-cell transplantation (HSCT) recipients, outcome of human cytomegalovirus (HCMV) infection results from balance between viral load/replication and pathogen-specific T-cell response. Using a cut-off of 30,000 HCMV DNA copies/ml blood for pre-emptive therapy and cut-offs of 1 and 3 virus-specific CD4(+) and CD8(+) T cells/μl blood for T-cell protection, we conducted in 131 young patients a prospective 3-year study aimed at verifying whether achievement of such immunological cut-offs protects from HCMV disease. In the first three months after transplantation, 55/89 (62%) HCMV-seropositive patients had infection and 36/55 (65%) were treated pre-emptively, whereas only 7/42 (17%) HCMV-seronegative patients developed infection and 3/7 (43%) were treated. After 12 months, 76 HCMV-seropositive and 9 HCMV-seronegative patients (cumulative incidence: 90% and 21%, respectively) displayed protective HCMV-specific immunity. Eighty of these 85 (95%) patients showed spontaneous control of HCMV infection without additional treatment. Five patients after reaching protective T-cell levels needed pre-emptive therapy, because they developed graft-versus-host disease (GvHD). HSCT recipients reconstituting protective levels of HCMV-specific T-cells in the absence of GvHD are no longer at risk for HCMV disease, at least within 3 years after transplantation. The decision to treat HCMV infection in young HSCT recipients may be taken by combining virological and immunological findings.     

Mechanisms of Cyclic Nucleotide Phosphodiesterases in Modulating T Cell Responses in Murine Graft-versus-Host Disease

Graft-versus-host disease (GvHD) is a key contributor to the morbidity and mortality after allogeneic hematopoetic stem cell transplantation (HSCT). Regulatory Foxp3⁺ CD4⁺ T cells (T_reg) suppress conventional T cell activation and can control GvHD. In our previous work, we demonstrate that a basic mechanism of T_reg mediated suppression occurs by the transfer of cyclic adenosine monophosphate (cAMP) to responder cells. Whether this mechanism is relevant for T_reg mediated suppression of GvHD is currently unknown. To address this question, bone marrow and T cells from C57BL/6 mice were transferred into lethally irradiated BALB/c recipients, and the course of GvHD and survival were monitored. Transplanted recipients developed severe GvHD that was strongly ameliorated by the transfer of donor T_reg cells. Towards the underlying mechanisms, in vitro studies revealed that T_reg communicated with DCs via gap junctions, resulting in functional inactivation of DC by a metabolic pathway involving cAMP that is modulated by the phosphodiesterase (PDE) 4 inhibitor rolipram. PDE2 or PDE3 inhibitors as well as rolipram suppressed allogeneic T cell activation, indirectly by enhancing T_reg mediated suppression of DC activation and directly by inhibiting responder T cell proliferation. In line with this, we observed a cooperative suppression of GvHD upon T_reg transfer and additional rolipram treatment. In conclusion, we propose that an important pathway of T_reg mediated control of GvHD is based on a cAMP dependent mechanism. These data provide the basis for future concepts to manipulate allogeneic T cell responses to prevent GvHD.     

A Case of Inguinal Sparganosis Mimicking Myeloid Sarcoma

We report here a case of inguinal sparganosis, initially regarded as myeloid sarcoma, diagnosed in a patient undergone allogeneic hematopoietic transplantation (HSCT). A 56-year-old male patient having myelodysplastic syndrome was treated with allogeneic HSCT after myeloablative conditioning regimen. At day 5 post-HSCT, the patient complained of a painless palpable mass on the left scrotum and inguinal area. Pelvic magnetic resonance imaging and computed tomography revealed suspected myeloid sarcoma. Gun-biopsy was performed, and the result revealed eosinophilic infiltrations without malignancy. Subsequent serologic IgG antibody test was positive for sparganum. Excisional biopsy as a therapeutic diagnosis was done, and the diagnosis of sparganosis was confirmed eventually. This is the first report of sparganosis after allogeneic HSCT mimicking myeloid sarcoma, giving a lesson that the physicians have to consider the possibility of sparganosis in this clinical situation and perform adequate diagnostic and therapeutic approaches.     

Clinical Assessment of Anti-Viral CD8+ T Cell Immune Monitoring Using QuantiFERON-CMV? Assay to Identify High Risk Allogeneic Hematopoietic Stem Cell Transplant Patients with CMV Infection Complications

The reconstitution of anti-viral cellular immunity following hematopoietic stem cell transplantation (HSCT) is crucial in preventing cytomegalovirus (CMV)-associated complications. Thus immunological monitoring has emerged as an important tool to better target pre-emptive anti-viral therapies. However, traditional laboratory-based assays are too cumbersome and complicated to implement in a clinical setting. Here we conducted a prospective study of a new whole blood assay (referred to as QuantiFERON-CMV®) to determine the clinical utility of measuring CMV-specific CD8+ T-cell responses as a prognostic tool. Forty-one evaluable allogeneic HSCT recipients underwent weekly immunological monitoring from day 21 post-transplant and of these 21 (51.2%) showed CMV reactivation and 29 (70.7%) developed acute graft-versus-host disease (GvHD). Patients with acute GvHD (grade≥2) within 6 weeks of transplant showed delayed reconstitution of CMV-specific T-cell immunity (p = 0.013) and a higher risk of CMV viremia (p = 0.026). The median time to stable CMV-specific immune reconstitution was 59 days and the incidence of CMV reactivation was lower in patients who developed this than those who did not (27% versus 65%; p = 0.031). Furthermore, a failure to reconstitute CMV-specific immunity soon after the onset of CMV viraemia was associated with higher peak viral loads (5685 copies/ml versus 875 copies/ml; p = 0.002). Hence, QuantiFERON-CMV® testing in the week following CMV viremia can be useful in identifying HSCT recipients at risk of complicated reactivation.     

Attributable risk estimation for adjusted disability multistate models: Application to nosocomial infections

Attributable risk has become an important concept in clinical epidemiology. In this paper, we suggest to estimate the attributable risk of nosocomial infections using a multistate approach. Recently, a multistate model (called progressive disability model in the literature) has been developed in order to take into consideration both the time‐dependency of the risk factor (e.g., nosocomial infections) and the presence of competing risks (e.g., death and discharge) at each time point. However, this approach does not take into account the possible heterogeneity of the study population. In this paper, we investigate an extension of this model and suggest an adjusted disability multistate model including covariates in each transition. This new multistate model has led us to define the concepts of overall and profiled attributable risk. We use a classical semiparametric approach to estimate the model and the new attributable risk. A simulation study is investigated and we show, in particular, that neglecting the presence of covariates when estimating the model can lead to an important bias. The methodology developed in this paper is applied to data on ventilator‐associated pneumonia in 12 French intensive care units.     

Review of Epidemiology, Diagnosis, and Treatment of Invasive Mould Infections in Allogeneic Hematopoietic Stem Cell Transplant Recipients

Invasive mould infections are a major cause of morbidity and mortality in hematopoietic stem cell transplant recipients (HSCT). Allogeneic HSCT recipients are at substantially higher risk than autologous HSCT recipients. Although neutropenia following the conditioning regimen remains an important risk factor for opportunistic fungal infections, most cases of invasive mould infection in allogeneic HSCT recipients occur after neutrophil recovery in the setting of potent immunosuppressive therapy for graft-versus-host disease. Invasive aspergillosis is the most common mould infection. However, there has been an increased incidence of less common non-Aspergillus moulds that include zygomycetes, Fusarium sp., and Scedosporium sp. Reflecting a key need, important advances have been made in the antifungal armamentarium. Voriconazole has become a new standard of care as primary therapy for invasive aspergillosis based on superiority over amphotericin B. There is significant interest in combination therapy for invasive aspergillosis pairing voriconazole or an amphotericin B formulation with an echinocandin. There have also been advances in novel diagnostic methods that facilitate early detection of invasive fungal infections that include galactomannan and beta-glucan antigen detection and PCR using fungal specific primers. We review the epidemiology, diagnosis, and management of invasive mould infection in HSCT, with a focus on allogeneic recipients. We also discuss options for prevention and early treatment of invasive mould infections.     

DNA immunization against tissue-restricted antigens enhances tumor immunity after allogeneic hemopoietic stem cell transplantation

Malignant relapse remains a major problem for recipients of allogeneic hemopoietic stem cell transplantation (HSCT). We hypothesized that immunization of allogeneic HSCT recipients against tissue-restricted Ags using DNA vaccines would decrease the risk of relapse without enhancing graft-vs-host disease (GVHD). Using the mouse B16 melanoma model, we found that post-HSCT DNA immunization against a single tumor Ag induces tumor rejection that is significantly greater than HSCT alone in a T cell-depleted MHC-matched minor Ag-mismatched allogeneic HSCT model (LP --> B6). In treatment models, post-HSCT DNA immunization provides significantly greater overall survival than the vaccine alone. Donor leukocyte infusion further enhances tumor-free survival, including in treatment models. There was no GVHD in HSCT recipients treated with DNA vaccination and donor leukocyte infusion. Further analysis demonstrated that these effects are dependent on CD8+ T cells of donor origin that recognize multiple epitopes. These results demonstrate that DNA immunization against tissue-restricted Ags after allogeneic T cell-depleted HSCT can induce potent antitumor effects without causing GVHD.     

Multicenter phase 1/2 application of adenovirus-specific T cells in high-risk pediatric patients after allogeneic stem cell transplantation

Background

Adenovirus (ADV) reactivation can cause significant morbidity and mortality in children after allogeneic stem cell transplantation. Antiviral drugs can control viremia, but viral clearance requires recovery of cell-mediated immunity.

Prediction errors for state occupation and transition probabilities in multi‐state models

In this paper, we consider the estimation of prediction errors for state occupation probabilities and transition probabilities for multistate time‐to‐event data. We study prediction errors based on the Brier score and on the Kullback–Leibler score and prove their properness. In the presence of right‐censored data, two classes of estimators, based on inverse probability weighting and pseudo‐values, respectively, are proposed, and consistency properties of the proposed estimators are investigated. The second part of the paper is devoted to the estimation of dynamic prediction errors for state occupation probabilities for multistate models, conditional on being alive, and for transition probabilities. Cross‐validated versions are proposed. Our methods are illustrated on the CSL1 randomized clinical trial comparing prednisone versus placebo for liver cirrhosis patients.     

Non-HLA gene polymorphisms and the outcome of allogeneic hemato-poietic stem cell transplantation

Haematopoietic stem cell transplantation (HSCT) is a curative treatment of many hematological disorders. However, although significant advances have been made in donor-recipient matching or conditioning regimens, HSCT is associated with a risk of post transplant complications. Those include generation of toxic lesions, graft-versus-host-disease (GvHD) and viral reactivations. Recent studies have shown the association between polymorphic features of non-HLA encoding genes and the incidence and severity of post-transplant complications in the recipients of allogeneic HSCT, implying that the donor-recipient genotyping, extended for cytokine loci, may be of prognostic value for the transplantation outcome. Thus, the pre-transplant analysis of the patients' genetic predisposition may be considered as important factor allowing the classification of the transplant recipients as less or more susceptible for developing toxic lesions, severe and/or fatal acute GvHD or viral reactivation. This review focuses on the relationship between the polymorphic patterns of tumor necrosis factor (TNF)- alpha and TNF-beta, IFN-gamma, interleukin (IL)-6, IL-10 and heat shock protein (HSP)70-hom encoding genes and the manifestation of post-transplant complications, acute and chronic GvHD, generation of toxic lesions, viral reactivations and mortality.     

Enhanced immune reconstitution by sex steroid ablation following allogeneic hemopoietic stem cell transplantation

Delayed immune reconstitution in adult recipients of allogeneic hemopoietic stem cell transplantations (HSCT) is related to age-induced thymic atrophy. Overcoming this paucity of T cell function is a major goal of clinical research but in the context of allogeneic transplants, any strategy must not exacerbate graft-vs-host disease (GVHD) yet ideally retain graft-vs-tumor (GVT) effects. We have shown sex steroid ablation reverses thymic atrophy and enhances T cell recovery in aged animals and in congenic bone marrow (BM) transplant but the latter does not have the complications of allogeneic T cell reactivity. We have examined whether sex steroid ablation promoted hemopoietic and T cell recovery following allogeneic HSCT and whether this benefit was negated by enhanced GVHD. BM and thymic cell numbers were significantly increased at 14 and 28 days after HSCT in castrated mice compared with sham-castrated controls. In the thymus, the numbers of donor-derived thymocytes and dendritic cells were significantly increased after HSCT and castration; donor-derived BM precursors and developing B cells were also significantly increased. Importantly, despite restoring T cell function, sex steroid inhibition did not exacerbate the development of GVHD or ameliorate GVT activity. Finally, IL-7 treatment in combination with castration had an additive effect on thymic cellularity following HSCT. These results indicate that sex steroid ablation can profoundly enhance thymic and hemopoietic recovery following allogeneic HSCT without increasing GVHD and maintaining GVT.     

Third-party umbilical cord blood–derived regulatory T cells prevent xenogenic graft-versus-host disease

Background aimsNaturally occurring regulatory T cells (Treg) are emerging as a promising approach for prevention of graft-versus-host disease (GvHD), which remains an obstacle to the successful outcome of allogeneic hematopoietic stem cell transplantation. However, Treg only constitute 1–5% of total nucleated cells in cord blood (CB) (<3 × 10⁶ cells), and therefore novel methods of Treg expansion to generate clinically relevant numbers are needed.MethodsSeveral methodologies are currently being used for ex vivo Treg expansion. We report a new approach to expand Treg from CB and demonstrate their efficacy in vitro by blunting allogeneic mixed lymphocyte reactions and in vivo by preventing GvHD through the use of a xenogenic GvHD mouse model.ResultsWith the use of magnetic cell sorting, naturally occurring Treg were isolated from CB by the positive selection of CD25⁺ cells. These were expanded to clinically relevant numbers by use of CD3/28 co-expressing Dynabeads and interleukin (IL)-2. Ex vivo–expanded Treg were CD4⁺25⁺FOXP3⁺127^lo and expressed a polyclonal T-cell receptor, Vβ repertoire. When compared with conventional T-lymphocytes (CD4⁺25⁻ cells), Treg consistently showed demethylation of the FOXP3 TSDR promoter region and suppression of allogeneic proliferation responses in vitro.ConclusionsIn our NOD-SCID IL-2Rγ^null xenogeneic model of GvHD, prophylactic injection of third-party, CB-derived, ex vivo–expanded Treg led to the prevention of GvHD that translated into improved GvHD score, decreased circulating inflammatory cytokines and significantly superior overall survival. This model of xenogenic GvHD can be used to study the mechanism of action of CB Treg as well as other therapeutic interventions.     

Allogeneic stem cell transplantation for multiple myeloma

The sensitivity of myeloma cells to high dose chemotherapy has led to the use of allogeneic hematopoietic stem cell transplantation (HSCT) as a therapeutic modality in this disease. In addition to providing more effective chemotherapy, the transplantation of allogeneic stem cells also initiates the development of an allogeneic immune response directed against residual myeloma cells. Direct evidence for a graft vs. myeloma (GVM) effect is provided by the ability of donor lymphocyte infusion (DLI) to induce significant responses in 30-50% of patients with myeloma who have relapsed after allogeneic HSCT. Nevertheless, allogeneic stem cell transplantation is also associated with a high incidence of transplant related toxicities, including regimen-related toxicities, graft vs. host disease (GVHD) and opportunistic infections. DLI has been shown to enhance immune reconstitution after allogeneic HSCT in addition to inducing a GVM response. Current efforts are directed at reducing the toxicities associated with allogeneic HSCT, identification of the target antigens of GVM and the development of new strategies to selectively enhance the immune response to myeloma cells.