Heat shock protein 70: correlation of expression with degree of graft-versus-host response and clinical graft-versus-host disease

A Human Skin Explant Test as a Novel In Vitro Assay for the Detection of Skin Sensitization to Aggregated Monoclonal Antibodies

Introduction: Monoclonal antibodies (mAbs) are important therapeutics. However, the enhanced potential for aggregation has become a critical quality parameter during the production of mAbs. Furthermore, mAb aggregation may also present a potential health risk in a clinical setting during the administration of mAb therapeutics to patients. While the extent of immunotoxicity in patient populations is uncertain, reports show it can lead to immune responses via cell activation and cytokine release. In this study, an autologous in vitro skin test designed to predict adverse immune events, including skin sensitization, was used as a novel assay for the assessment of immunotoxicity caused by mAb aggregation. Material and Methods: Aggregation of mAbs was induced by a heat stress protocol, followed by characterization of protein content by analytical ultra-centrifugation and transmission electron microscopy, revealing a 4% aggregation level of total protein content. Immunotoxicity and potential skin sensitization caused by the aggregates, were then tested in a skin explant assay. Results: Aggregated Herceptin and Rituximab caused skin sensitization, as shown by histopathological damage (grade II-III positive response) together with positive staining for Heat Shock Protein 70 (HSP70). Changes in T cell proliferation were not observed. Cytokine analysis revealed a significant increase of IL-10 for the most extreme condition of aggregation (65 °C at pH3) and a trend for an overall increase of IFN-γ, especially in response to Rituximab. Conclusions: The skin explant assay demonstrated that aggregated mAbs showed adverse immune reactions, as demonstrated as skin sensitization, with histopathological grades II-III. The assay may, therefore, be a novel tool for assessing immunotoxicity and skin sensitization caused by mAb aggregation.

Review of Genetic Variation as a Predictive Biomarker for Chronic Graft-Versus-Host-Disease After Allogeneic Stem Cell Transplantation

Chronic graft-versus-host disease (cGvHD) is one of the major complications of allogeneic stem cell transplantation (HSCT). cGvHD is an autoimmune-like disorder affecting multiple organs and involves a dermatological rash, tissue inflammation and fibrosis. The incidence of cGvHD has been reported to be as high as 30% to 60% and there are currently no reliable tools for predicting the occurrence of cGvHD. There is therefore an important unmet clinical need for predictive biomarkers. The present review summarizes the state of the art for genetic variation as a predictive biomarker for cGvHD. We discuss three different modes of action for genetic variation in transplantation: genetic associations, genetic matching, and pharmacogenetics. The results indicate that currently, there are no genetic polymorphisms or genetic tools that can be reliably used as validated biomarkers for predicting cGvHD. A number of recommendations for future studies can be drawn. The majority of studies to date have been under-powered and included too few patients and genetic markers. Like in all complex multifactorial diseases, large collaborative genome-level studies are now needed to achieve reliable and unbiased results. Some of the candidate genes, in particular, CTLA4, HSPE, IL1R1, CCR6, FGFR1OP, and IL10, and some non-HLA variants in the HLA gene region have been replicated to be associated with cGvHD risk in independent studies. These associations should now be confirmed in large well-characterized cohorts with fine mapping. Some patients develop cGvHD despite very extensive immunosuppression and other treatments, indicating that the current therapeutic regimens may not always be effective enough. Hence, more studies on pharmacogenetics are also required. Moreover, all of these studies should be adjusted for diagnostic and clinical features of cGvHD. We conclude that future studies should focus on modern genome-level tools, such as machine learning, polygenic risk scores and genome-wide association study-transcription meta-analyses, instead of focusing on just single variants. The risk of cGvHD may be related to the summary level of immunogenetic differences, or whole genome histocompatibility between each donor-recipient pair. As the number of genome-wide analyses in HSCT is increasing, we are approaching an era where there will be sufficient data to incorporate these approaches in the near future.

Characterization of monocyte subtypes regarding their phenotype and development in the context of graft-versus-host disease

Graft-versus-host disease (GvHD) is a major cause of morbidity and mortality after allogeneic hematopoietic cell transplantation (HCT). In this study, monocyte subtypes were characterized regarding cytokine expression pattern and development in the context of GvHD. Using inflammatory S100 proteins for monocyte stimulation, it could be demonstrated that intermediate monocytes are the main producers of inflammatory cytokines such as IL-6 and TNFα known to be involved in the development of Th17 cells pointing towards an inflammatory phenotype of this monocyte subtype. Furthermore, novel aspects regarding monocyte subtype development were found. Our data reveal that prednisolone promotes the induction of intermediate monocytes from classical monocytes which correlates with HSP70 expression levels. However, 1α,25-Dihydroxyvitamin D3 treatment results in the abrogation of the prednisolone-mediated induction of this inflammatory monocyte subset and low HSP70 expression levels. Treatment of classical monocytes with pifithrin-μ, a specific HSP70 inhibitor, also leads to an inhibited induction of intermediate monocytes in the presence of prednisolone. These data point towards a predominant role of HSP70 in the development of intermediate monocytes. Thus, HSP70 might be a promising target for GvHD therapy, especially in combination with glucocorticoids, in order to decrease intermediate monocyte subset levels.

Serum Gp96 is a chaperone of complement-C3 during graft-versus-host disease

Better identification of severe acute graft-versus-host disease (GvHD) may improve the outcome of this life-threatening complication of allogeneic hematopoietic stem cell transplantation. GvHD induces tissue damage and the release of damage-associated molecular pattern (DAMP) molecules. Here, we analyzed GvHD patients (n = 39) to show that serum heat shock protein glycoprotein 96 (Gp96) could be such a DAMP molecule. We demonstrate that serum Gp96 increases in gastrointestinal GvHD patients and its level correlates with disease severity. An increase in Gp96 serum level was also observed in a mouse model of acute GvHD. This model was used to identify complement C3 as a main partner of Gp96 in the serum. Our biolayer interferometry, yeast two-hybrid and in silico modeling data allowed us to determine that Gp96 binds to a complement C3 fragment encompassing amino acids 749-954, a functional complement C3 hot spot important for binding of different regulators. Accordingly, in vitro experiments with purified proteins demonstrate that Gp96 downregulates several complement C3 functions. Finally, experimental induction of GvHD in complement C3-deficient mice confirms the link between Gp96 and complement C3 in the serum and with the severity of the disease.

Danger Signals and Graft-versus-host Disease: Current Understanding and Future Perspectives

Graft-versus-host response after allogeneic hematopoietic stem cell transplantation (allo-HCT) represents one of the most intense inflammatory responses observed in humans. Host conditioning facilitates engraftment of donor cells, but the tissue injury caused from it primes the critical first steps in the development of acute graft-versus-host disease (GVHD). Tissue injuries release pro-inflammatory cytokines (such as TNF-α, IL-1β, and IL-6) through widespread stimulation of pattern recognition receptors (PRRs) by the release of danger stimuli, such as damage-associated molecular patterns (DAMPs) and pathogen-associated molecular patterns (PAMPs). DAMPs and PAMPs function as potent stimulators for host and donor-derived antigen presenting cells (APCs) that in turn activate and amplify the responses of alloreactive donor T cells. Emerging data also point towards a role for suppression of DAMP induced inflammation by the APCs and donor T cells in mitigating GVHD severity. In this review, we summarize the current understanding on the role of danger stimuli, such as the DAMPs and PAMPs, in GVHD.

Soluble heat shock protein 70 members in patients undergoing allogeneic hematopoietic cell transplantation

BACKGROUND

Heat shock proteins (HSP) are highly conserved immunogenic proteins serving as potent danger signals. They are upregulated under stress conditions like fever and hypoxia. Extracellular HSP are involved in antigen presentation, cytokine release and maturation of antigen presenting cells.

METHODS

The release of the inducible members of the HSP70 family, Hsp72 and Hsp70B', into the serum of 20 patients undergoing allogeneic hematopoietic cell transplantation and 20 healthy donors was evaluated using enzyme linked immunosorbent assay (ELISA) kits.

RESULTS

Eight patients (40%) did not receive anti-thymocyte globulin (ATG) for prophylaxis of graft versus host disease (GvHD). These patients had no detectable or low serum levels of Hsp72 (n=3, 0.03 to 1.92ng/ml) which were in line with levels detected in 20 healthy individuals (p=0.07). Measurable HSP was not associated with any medication or transplantation-related procedures. In twelve patients (60%) receiving ATG, detected high levels of HSP reflected cross-reactivity of the rabbit-derived ATG with the anti-rabbit antibody used in the ELISA.

CONCLUSIONS

Assumed HSP70 expression detected such ELISA has to be regarded carefully after ATG application. Neither radiochemotherapy, nor inflammation or sepsis during aplasia induced HSP70 release into the serum. Thus, soluble HSP70 may not be involved in the pathogenesis of acute GvHD.

The role of danger signals and ectonucleotidases in acute graft-versus-host disease

Allogeneic hematopoietic cell transplantation (allo-HCT) represents the only curative treatment approach for many patients with benign or malignant diseases of the hematopoietic system. However, post-transplant morbidity and mortality are significantly increased by the development of acute graft-versus-host disease (GvHD). While alloreactive T cells act as the main cellular mediator of the GvH reaction, recent evidence suggests a critical role of the innate immune system in the early stages of GvHD initiation. Danger-associated molecular patterns released from the intracellular space as well as from the extracellular matrix activate antigen-presenting cells and set pro-inflammatory pathways in motion. This review gives an overview about danger signals representing therapeutic targets with a clinical perspective with a particular focus on extracellular nucleotides and ectonucleotidases.

Innate immune activation by tissue injury and cell death in the setting of hematopoietic stem cell transplantation

Allogeneic hematopoietic stem cell transplantation (Allo-HSCT) with donor lymphocyte infusion is the mainstay of treatment for many types of hematological malignancies, but the therapeutic effect and prevention of relapse is complicated by donor T-cell recognition and attack of host tissue in a process known as graft-versus-host disease (GvHD). Cytotoxic myeloablative conditioning regimens used prior to Allo-HSCT result in the release of endogenous innate immune activators that are increasingly recognized for their role in creating a pro-inflammatory milieu. This increased inflammatory state promotes allogeneic T-cell activation and the induction and perpetuation of GvHD. Here, we review the processes of cellular response to injury and cell death that are relevant following Allo-HSCT and present the current evidence for a causative role of a variety of endogenous innate immune activators in the mediation of sterile inflammation following Allo-HSCT. Finally, we discuss the potential therapeutic strategies that target the endogenous pathways of innate immune activation to decrease the incidence and severity of GvHD following Allo-HSCT.

Elevated level of HSPA1L mRNA correlates with graft-versus-host disease

Graft-versus-host disease (GVHD) can be a fatal complication of allogeneic stem cell transplantation (allo-HSCT). GVHD can be classified as acute (aGVHD: up to 100 days) or chronic (cGVHD: after 100 days) based on the time-point of disease occurrence. At present there are a limited number of biomarkers available for use in the clinic. Thus, the aim of this research was to evaluate the biomarker potential of the extensively studied Heat Shock Protein 70 family members (HSPA1A/HSPA1B and HSPA1L) at the messenger RNA (mRNA) level in acute and cGVHD patient cohorts. In the skin biopsies, HSPA1L mRNA expression was lower in patients with severe aGVHD (grades II-III) when compared to those with none or low grade aGVHD (grades 0-I) and normal controls. In whole blood, HSPA1L mRNA expression level was significantly (p = 0.008) up-regulated at 28 days post-transplant in cGVHD patients with a significant area under the curve (AUC = 0.773). In addition, HSPA1B expression in whole blood was significantly higher at 3 months post-transplant in both the aGVHD grade II-III (p = 0.012) and cGVHD (p = 0.027) patients. Our initial results in this small cohort show that quantifying HSPA1L mRNA expression in the whole blood of allo-HSCT patients at day 28 post-allo-HSCT may be a useful predictive biomarker for cGVHD.

Various forms of tissue damage and danger signals following hematopoietic stem-cell transplantation

Hematopoietic stem-cell transplantation (HSCT) is the most potent curative therapy for many malignant and non-malignant disorders. Unfortunately, a major complication of HSCT is graft-versus-host disease (GVHD), which is mediated by tissue damage resulting from the conditioning regimens before the transplantation and the alloreaction of dual immune components (activated donor T-cells and recipient’s antigen-presenting cells). This tissue damage leads to the release of alarmins and the triggering of pathogen-recognition receptors that activate the innate immune system and subsequently the adaptive immune system. Alarmins, which are of endogenous origin, together with the exogenous pathogen-associated molecular patterns (PAMPs) elicit similar responses of danger signals and represent the group of damage-associated molecular patterns (DAMPs). Effector cells of innate and adaptive immunity that are activated by PAMPs or alarmins can secrete other alarmins and amplify the immune responses. These complex interactions and loops between alarmins and PAMPs are particularly potent at inducing and then aggravating the GVHD reaction. In this review, we highlight the role of these tissue damaging molecules and their signaling pathways. Interestingly, some DAMPs and PAMPs are organ specific and GVHD-induced and have been shown to be interesting biomarkers. Some of these molecules may represent potential targets for novel therapeutic approaches.

Amygdalin analogues inhibit IFN-γ signalling and reduce the inflammatory response in human epidermal keratinocytes

Peptide T (PT), an octapeptide fragment located in the V2 region of the HIV-1 gp120-coating protein, appears to be beneficial in the treatment of psoriasis. Our previous investigations suggest that keratinocytes play a key role in conditioning the therapeutic effects of PT in psoriasis. The aim of this study was to explore the effects of PT and the peptidomimetic natural products, Dhurrin and Prunasin, on the expression of the IL-6, IL-8, IL-23, HSP70 and ICAM-1 on IFN-γ and TNF-α-NHEK activated cells. Moreover, we analysed the interference of PT and its analogues through STAT-3 activation. Our results show that the analogues tested exhibit the beneficial biological effects of PT, suggesting the primary role of keratinocytes upon which PT and the peptidomimetics act directly, by reducing proinflammatory responses. Its reduction appears to be important for therapeutic approach in psoriasis pathogenesis.

Siglec-G-CD24 axis controls the severity of graft-versus-host disease in mice

Activation of sialic-acid-binding immunoglobulin-like lectin-G (Siglec-G) by noninfectious damage-associated molecular patterns controls innate immune responses. However, whether it also regulates T-cell-mediated adaptive immune responses is not known. Graft-versus-host reaction is a robust adaptive immune response caused by allogeneic hematopoietic cell transplantation that have been activated by antigen-presenting cells (APCs) in the context of damaged host tissues following allogeneic hematopoietic cell transplantation. The role of infectious and noninfectious pattern recognition receptor-mediated activation in the induction and aggravation of graft-versus-host disease (GVHD) is being increasingly appreciated. But the role of pathways that control innate immune responses to noninfectious stimuli in modulating GVHD has heretofore not been recognized. We report that Siglec-G expression on host APCs, specifically on hematopoietic cells, negatively regulates GVHD in multiple clinically relevant murine models. Mechanistic studies with various relevant Siglec-G and CD24 knockout mice and chimeric animals, along with rescue experiments with novel CD24 fusion protein demonstrate that enhancing the interaction between Siglec-G on host APCs with CD24 on donor T cells attenuates GVHD. Taken together, our data demonstrate that Siglec-G-CD24 axis, controls the severity of GVHD and suggest that enhancing this interaction may represent a novel strategy for mitigating GVHD.

Pathogenesis of graft-versus-host disease: innate immunity amplifying acute alloimmune responses

In addition to reduced-intensity conditioning, which has expanded the eligibility for hematopoietic cell transplantation (HCT) to older patients, increased availability of alternative donors, including HLA-mismatched unrelated donors, has increased access to allogeneic HCT for more patients. However, acute graft-versus-host disease (GVHD) remains a lethal complication, even in HLA-matched donor-recipient pairs. The pathophysiology of GVHD depends on aspects of adaptive immunity and interactions between donor T-cells and host dendritic cells (DCs). Recent work has revealed that the role of other immune cells and endothelial cells and components of the innate immune response are also important. Tissue damage caused by the conditioning regimen leads to the release of exogenous and endogenous "danger signals". Exogenous danger signals called pathogen-associated molecular patterns and endogenous noninfectious molecules known as damage-associated molecular patterns (DAMPs) are responsible for initiating or amplifying acute GVHD by enhancing DC maturation and alloreactive T-cell responses. A significant association of innate immune receptor polymorphisms with outcomes, including GVHD severity, was observed in patients receiving allogeneic HCT. Understanding of the role of innate immunity in acute GVHD might offer new therapeutic approaches.

Aberrant expression and secretion of heat shock protein 90 in patients with bullous pemphigoid

The cell stress chaperone heat shock protein 90 (Hsp90) has been implicated in inflammatory responses and its inhibition has proven successful in different mouse models of autoimmune diseases, including epidermolysis bullosa acquisita. Here, we investigated expression levels and secretory responses of Hsp90 in patients with bullous pemphigoid (BP), the most common subepidermal autoimmune blistering skin disease. In comparison to healthy controls, the following observations were made: (i) Hsp90 was highly expressed in the skin of BP patients, whereas its serum levels were decreased and inversely associated with IgG autoantibody levels against the NC16A immunodominant region of the BP180 autoantigen, (ii) in contrast, neither aberrant levels of circulating Hsp90 nor any correlation of this protein with serum autoantibodies was found in a control cohort of autoimmune bullous disease patients with pemphigus vulgaris, (iii) Hsp90 was highly expressed in and restrictedly released from peripheral blood mononuclear cells of BP patients, and (iv) Hsp90 was potently induced in and restrictedly secreted from human keratinocyte (HaCaT) cells by BP serum and isolated anti-BP180 NC16A IgG autoantibodies, respectively. Our results reveal an upregulated Hsp90 expression at the site of inflammation and an autoantibody-mediated dysregulation of the intracellular and extracellular distribution of this chaperone in BP patients. These findings suggest that Hsp90 may play a pathophysiological role and represent a novel potential treatment target in BP.

The immunosuppressive activity of heat shock protein 70

Heat shock protein 70 (HSP70) has previously been described as a potent antitumour vaccine. The mechanism relied on the ability of tumour derived HSP70 to associate with antigenic peptides, which, when cross presented, elicited a T cell mediated antitumour response. Subsequently, HSP70 was incorrectly described as a potent adjuvant of innate immunity, and although mistakes in the experimental approaches were exposed and associated with endotoxin contamination in the recombinant HSP70 specimen, questions still remain regarding this matter. Here we review only publications that have cautiously addressed the endotoxin contamination problem in HSP70 in order to reveal the real immunological function of the protein. Accordingly, “endotoxin free” HSP70 stimulates macrophages and delivers antigenic peptides to APCs, which effectively prime T cells mediating an antitumour reaction. Conversely, HSP70 has potent anti-inflammatory functions as follows: regulating T cell responses, reducing stimulatory capacity of DCs, and inducing development of immunosuppressive regulatory T cells. These activities were further associated with the immune evasive mechanism of tumours and implicated in the modulation of immune reactivity in autoimmune diseases and transplant-related clinical conditions. Consequently, the role of HSP70 in immune regulation is newly emerging and contrary to what was previously anticipated.

Immune reconstitution and graft-versus-host reactions in rat models of allogeneic hematopoietic cell transplantation

Allogeneic hematopoietic cell transplantation (alloHCT) extends the lives of thousands of patients who would otherwise succumb to hematopoietic malignancies such as leukemias and lymphomas, aplastic anemia, and disorders of the immune system. In alloHCT, different immune cell types mediate beneficial graft-versus-tumor (GvT) effects, regulate detrimental graft-versus-host disease (GvHD), and are required for protection against infections. Today, the “good” (GvT effector cells and memory cells conferring protection) cannot be easily separated from the “bad” (GvHD-causing cells), and alloHCT remains a hazardous medical modality. The transplantation of hematopoietic stem cells into an immunosuppressed patient creates a delicate environment for the reconstitution of donor blood and immune cells in co-existence with host cells. Immunological reconstitution determines to a large extent the immune status of the allo-transplanted host against infections and the recurrence of cancer, and is critical for long-term protection and survival after clinical alloHCT. Animal models continue to be extremely valuable experimental tools that widen our understanding of, for example, the dynamics of post-transplant hematopoiesis and the complexity of immune reconstitution with multiple ways of interaction between host and donor cells. In this review, we discuss the rat as an experimental model of HCT between allogeneic individuals. We summarize our findings on lymphocyte reconstitution in transplanted rats and illustrate the disease pathology of this particular model. We also introduce the rat skin explant assay, a feasible alternative to in vivo transplantation studies. The skin explant assay can be used to elucidate the biology of graft-versus-host reactions, which are known to have a major impact on immune reconstitution, and to perform genome-wide gene expression studies using controlled combinations of minor and major histocompatibility between the donor and the recipient.

Genetics of graft-versus-host disease: the major histocompatibility complex

Graft-versus-host disease (GVHD) is a potentially life-threatening complication of allogeneic hematopoietic cell transplantation. Many genes are presumed to be involved in GVHD, but the best characterized genetic system is that of the human major histocompatibility complex (MHC) located on chromosome 6. Among the hundreds of genes located within the MHC region, the best known and characterized are the classical HLA genes, HLA-A, C, B, DRB1, DQB1, and DPB1. They play a fundamental role in T cell immune responses, and HLA-A, C, and B also function as ligands for the natural killer cell immunoglobulin-like receptors involved in innate immunity. This review highlights the state-of-the art in the field of histocompatibility and immunogenetics of the MHC with respect to genetic risk factors for GVHD.

Optimizing management of myelodysplastic syndromes post-allogeneic transplantation

Allogeneic hematopoietic stem cell transplantation is still the only potentially curative treatment for patients with myelodysplastic syndromes. Improvements in donor selection, supportive care and the introduction of reduced-intensity conditioning have led to a decrease in early transplant mortality. However, relapse rates have not changed significantly in recent years. Furthermore, treatment options for patients relapsing after hematopoietic stem cell transplantation are limited and often short-lived. Thus, optimizing the post-transplant outcome by maintenance approaches or minimal residual disease-directed preemptive therapy is an important goal of current clinical research. Further strategies aiming at an improved prevention of graft-versus-host disease are currently under investigation.

Inducible heat shock protein 70 reduces T cell responses and stimulatory capacity of monocyte-derived dendritic cells

Heat shock protein 70 (Hsp70) has gained a lot of attention in the past decade due to its potential immunoregulatory functions. Some of the described proinflammatory functions of Hsp70 became controversial as they were based on recombinant Hsp70 proteins specimens, which were later shown to be endotoxin-contaminated. In this study we used low endotoxin inducible Hsp70 (also known as Hsp72, HSPA1A), and we observed that after a 24-h incubation of monocyte-derived immature dendritic cells (mo-iDCs) with 20 μg/ml of low endotoxin Hsp70, their ability to stimulate allogenic T cells was reduced. Interestingly, low endotoxin Hsp70 also significantly reduced T cell responses when they were simulated with either IL-2 or phytohemagglutinin, therefore showing that Hsp70 could alter T cell responses independently from its effect on mo-iDCs. We also reported a greater response of Hsp70 treatment when activated versus nonactivated T cells were used. This effect of Hsp70 was similar for all tested populations of T cells that included CD3(+), CD4(+), or CD8(+). Taken together, our observations strongly suggest that Hsp70 might dampen, rather than provoke, T cell-mediated inflammatory reactions in many clinical conditions where up-regulation of Hsp70 is observed.

Patient HSP70-hom TG haplotype is associated with decreased transplant-related mortality and improved survival after sibling HLA-matched hematopoietic stem cell transplantation

Heat shock protein 70-hom (HSP70-hom) plays an important role in protein folding and immune responses. Therefore, HSP70-hom gene polymorphisms may act as important factors in predicting the prognosis of patients receiving allogeneic hematopoietic stem cell transplantation (HSCT). To evaluate the role of HSP70-hom gene polymorphisms in the prognosis of patients receiving sibling human leukocyte antigen (HLA)-matched allogeneic HSCT, the HSP70-hom polymorphisms, T2437C and G2763A, were genotyped in 147 patients receiving sibling HLA-matched allogeneic HSCT. Individual diplotypes were estimated from genotype data of the two HSP70-hom polymorphisms using the expectation maximization algorithm. Patients with the 2763GG or GA genotype showed longer overall survival compared with those with the 2763AA genotype, and patients with a TG haplotype (TG/TA, TG/TG or TG/CG) also showed longer overall survival compared with those with a non-TG haplotype (TA/TA or TA/CG) (both G2763A genotype and diplotype, p<0.01). Moreover, the 2437TT genotype was found to be protective for treatment-related death compared with the 2437TC genotype, and a TG haplotype was found to be very protective for treatment-related death compared with a non-TG haplotype (T2437C genotype, p=0.04; and diplotype, p=0.02). Therefore, our results suggest that HSP70-hom polymorphisms play an important role in the prognosis of patients receiving sibling HLA-matched allogeneic HSCT.

The role of heat shock protein 27 in bronchiolitis obliterans syndrome after lung transplantation

BACKGROUND

Heat shock proteins (Hsps) are a family of evolutionary conserved proteins classified according to their size as small and large Hsps. They have a cytoprotective role and have been shown to be immunogenic molecules. In addition, self-reactivity to Hsps has been implicated in various autoimmune diseases and in the development of alloimmunity. This study examined the relationship of large and small Hsps and anti-Hsp antibodies in lung transplant (LTx) recipients who have bronchiolitis obliterans syndrome (BOS).

METHODS

Anti-Hsp27 and Hsp70 antibodies, and Hsp27, Hsp60, and Hsp70 protein expression levels were evaluated in serum and bronchoalveolar lavage samples collected from 8 LTx recipients with established BOS and 8 recipients without BOS (controls). Serum from 8 healthy individuals was examined for Hsp levels as a comparison.

RESULTS

Elevated serum Hsp27 levels were observed in recipients with BOS compared with controls or healthy individuals, whereas Hsp70 and Hsp60 expression showed no difference. Anti-Hsp27 antibody levels were significantly higher in the BAL of recipients with BOS than in those without BOS. In contrast, anti-Hsp70 antibodies levels in serum or BAL showed no difference between groups.

CONCLUSIONS

These results support the novel concept that Hsp27, but not the classic Hsp60 and Hsp70, may be associated with the development BOS. The expression of anti-Hsp27 antibodies found only in the BAL fluid suggests a local response occurring at the level of the alveoli and terminal airways.

Investigating cellular stress responses--a multidisciplinary approach from basic science to therapeutics--report on the EuroSciCon (European Scientific Conferences) meeting

The meeting on "Investigating cellular stress responses--a multidisciplinary approach from basic science to therapeutics" was held in London on 13 October 2006. The purpose of this 1-day meeting was to bring together European scientists investigating the immune biology of stress proteins and their potential clinical applications. The main topics included: the role of heat shock proteins (Hsps) in bacterial infections; the role of Hsps with a molecular mass of about 70 kDa in cancer therapy and in prediction of the clinical outcome following allogeneic hematopoietic stem cell transplantation; the quality and duration of stress as a danger signal for the initiation of a stress response; the mechanism of Hsp-protein interaction; and Hsp export from tumor cells in secretory granules.

Proteomic patterns predict acute graft-versus-host disease after allogeneic hematopoietic stem cell transplantation

Acute graft-versus-host disease (aGvHD) contributes significantly to morbidity and mortality after allogeneic hematopoietic stem cell transplantation (allo-HSCT). Diagnosis of GvHD is mainly based on clinical features and tissue biopsies. A noninvasive, unbiased laboratory test for GvHD diagnosis does not exist. Here we describe the application of capillary electrophoresis coupled online with mass spectrometry (CE-MS) to 13 samples from 10 patients with aGvHD of grade II or more and 50 control samples from 23 patients without GvHD. About 170 GvHD-specific polypeptides were detected and a tentatively aGvHD-specific model consisting of 31 polypeptides was chosen, allowing correct classification of 13 of 13 (sensitivity 100.0% [95% confidence interval {CI} 75.1 to 100.0]) aGvHD samples and 49 of 50 (specificity 98.0% [95% CI 89.3 to 99.7]) control samples of the training set. The subsequent blinded evaluation of 599 samples enabled diagnosis of aGvHD greater than grade II, even prior to clinical diagnosis, with a sensitivity of 83.1% (95% CI 73.1 to 87.9) and a specificity of 75.6% (95% CI 71.6 to 79.4). Thus, high-resolution proteome analysis represents an unbiased laboratory-based screening method, enabling diagnosis, and possibly enabling preemptive therapy.

Antibodies to 60, 65 and 70 kDa heat shock proteins in pediatric allogeneic stem cell transplant recipients

Allogeneic SCT remains the only means of cure for many patients with various malignant disorders as well as non-malignant diseases. Infection together with severe aGvHD may result in a significant incidence of transplant-related morbidity and mortality. Current evidence suggests that hSPS represent major immunodominant antigens in many pathogens and therefore might play an important role in the pathogenesis of GvHD. We investigated the levels of total Ig, IgG and IgM isotype antibodies to rh-hsp60, recombinant Mycobacterium bovis hsp65 and stress-inducible rh-hsp70 in sera of pediatric patients undergoing SCT by using ELISA. We studied whether humoral immune responses to hSPS follow transplant-related complications, bacterial and fungal infection. Anti-hsp antibodies were detected in patients' sera before conditioning, over the course of conditioning and all the time post-transplant. We found no correlation between anti-hsp antibodies and the occurrence and severity of GvHD and/or other transplant-related complications like graft failure, hemorrhagic cystitis and capillary leakage syndrome. However, elevated anti-hsp antibodies involving IgM and IgG isotypes were found to be associated with bacterial and fungal infection depending on etiological agents. We demonstrated de novo humoral response to hSPS in a cohort of patients with actual infection caused by Klebsiella pneumoniae (anti-hsp60, anti-hsp65 and anti-hsp70), Pseudomonas aeruginosa (anti-hsp60, anti-hsp70) and Aspergillus fumigatus (anti-hsp65). We conclude that anti-hsp antibodies might be produced after SCT in relation to infection depending on etiological agents; however, transplant-related complications by themselves had a little impact.

Detection of antibodies against 60-, 65- and 70-kDa heat shock proteins in paediatric patients with various disorders using Western blotting and ELISA

BACKGROUND

We examined antibodies against 60-, 65- and 70-kDa heat shock proteins (HSPs) in paediatric healthy individuals, patients with juvenile idiopathic arthritis (JIA) and those undergoing allogeneic stem-cell transplantation for various malignant and non-malignant diseases.

METHODS

Western blotting and ELISA were used to examine HSP-directed humoral immune responses.

RESULTS

Using ELISA we detected anti-Hsp60, -Hsp65 and -Hsp70 IgG antibodies in patient sera before, during and after conditioning and at all post-transplant times, as well as in JIA patients and controls. Western blotting showed positivity for anti-Hsp60 and anti-Hsp65 antibodies in all samples with a HSP concentration of 0.5 microg/lane. However, anti-Hsp70 antibodies were not detected at all when both sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and native PAGE were used, except for one JIA patient, for whom a positive signal was only achieved in native PAGE when Hsp70 was increased to 2 microg/lane and serum dilution decreased to 1:10.

CONCLUSION

Western blotting is convenient for the detection of anti-Hsp60 and anti-Hsp65 antibodies, but it is not sensitive enough for the detection of anti-Hsp70 antibodies. ELISA, which is more sensitive, might be preferentially used to screen anti-Hsp60, -Hsp65 and -Hsp70 antibodies in sera of children with various disorders.

Peripheral blood mononuclear cell responses to heat shock proteins in patients undergoing stem cell transplantation

GVHD is a major complication after allogeneic SCT. Etiology of GVHD is multifactorial. Known role of hSPS in antigen presentation could suggest their potential role in the alloreactive process that leads to aGVHD. HSPS represent major immunodominant antigens in a wide spectrum of microbial pathogens. Bacterial and fungal colonization, infection and sepsis are frequent in immunocompromised patients with various malignant and non-malignant diseases. We studied PBMC responses to recombinant human hsp60 (rh-hsp60), rh-hsp70 and Mycobacterium bovis hsp65 (M. bovis hsp65) in relation to aGVHD and infection in 34 pediatric patients with various lympho-hemopoietic malignancies as well as non-malignant disorders subjected to SCT. PBMC of patients before initiation of preparative regimen as well as after engraftment were stimulated with hSPS (1 microg/mL/well, 7-day cultivation). PHA was used as a control of the stimulation ability. Cell responses were measured after the incorporation of 3H-thymidin (pulsing with 1 microCi/well) and were expressed as stimulation indexes (SI). We demonstrated significantly high proliferative response to rh-hsp60 as well as M. bovis hsp65 in a cohort of pretransplant patients with anamnestic and/or actual infection when compared with a cohort of patients without infection and healthy individuals. Strong PBMC cell responses to hSPS were found in patients who were at present colonized with Escherichia coli and Klebsiella pneumoniae or had previously K. pneumoniae infection with subsequent sepsis. Our findings support various studies dealing with immunodominant hSPS in connection with several pathogens and infectious diseases. Although no statistical difference for proliferative response to PHA was observed, PBMC responses against all tested hSPS comparing a cohort of patients with aGVHD and that with no sign of GVHD resulted in significantly lower SI for all tested hSPS in patients with aGVHD. Lower stimulation with hSPS during aGVHD might be explained by the stress-induced upregulation of self-hSPS synthesis that might lead to the inhibition of self-hSPS reactive T-cell response. Vice versa, we hypothesize that increased hsp-specific stimulation may reflect the presence of protecting regulatory T cells preventing the development of Th1-mediated diseases involving aGVHD.

HSP70-hom gene polymorphism in allogeneic hematopoietic stem-cell transplant recipients correlates with the development of acute graft-versus-host disease

BACKGROUND

A number of genetic polymorphisms have been shown to be associated with the outcome after allogeneic hematopoietic stem-cell transplantation (HSCT). In the present study, HSP70-hom polymorphism (+2763 G/A) was analyzed in the patients and donors of allogeneic HSCT in relation to transplantation outcome, susceptibility for generation of severe toxic lesions, and acute (a) graft-versus-host disease (GVHD).

METHODS

One hundred thirty-three recipients of allogeneic hematopoietic stem cells and 64 haploidentical and matched unrelated donors were investigated. All these individuals were typed for dimorphism within the HSP70-hom gene (+2763 G/A) with the use of amplification refractory mutation system technique. RESULTS.: Patients with the HSP-AA homozygous genotype presented more frequently with grade II to IV toxic lesions (12 of 14 vs. 61 of 105, P = 0.039) and aGVHD (12 of 16 vs. 56 of 114, P = 0.045). Conversely, DRB1*11 was associated with a lower risk of aGVHD manifestation (10 of 31 vs. 58 of 99, P = 0.009). These contrary associations of HSP-AA and DRB1*11 with the risk of aGVHD were confirmed using logistic regression modeling in multivariable analysis (HSP-AA, odds ratio [OR] = 3.833, P = 0.004; DRB1*11, OR = 0.224, P = 0.048). None of donor HSP genotypes or patient-donor incompatibility within HSP alleles was associated with susceptibility to toxic complications or aGVHD.

CONCLUSIONS

Polymorphism of the HSP70-hom gene is associated with the development of posttransplant complications. Recipient HSP-AA homozygous genotype is a risk factor for aGVHD.

Graft-versus-host disease of the skin: life and death on the epidermal edge

Despite impressive advances in the field of allogeneic hematopoietic transplantation, graft versus host disease (GVHD) remains a significant obstacle to be overcome; it would enhance the safety and efficacy of this life-saving therapy. This review provides a framework for understanding the molecular and cellular basis underlying GVHD. We propose a 3-phase model of GVHD that highlights the importance of the conditioning regimen on the recipient tissues administered prior to infusion of donor bone marrow inoculum. A novel skin explant model, designed to take into consideration the immunobiological consequences of conditioning regimens on resident host cells, is proposed to advance our understanding of GVHD and serve as a potential prognostic tool when allogeneic recipient/donor combinations are being contemplated in the clinic. Within this review, specific emphasis is placed on the importance of defining the apoptotic machinery engaged in epidermal keratinocytes triggered by both conditioning regimens, and by host resident and recruited immunocytes and soluble mediators produced at sites of injury. The review is completed with a working model for cutaneous GVHD. Although the skin is highlighted because of its accessibility for clinical observations and serial sampling opportunities, lessons learned from studies of cutaneous GVHD are likely to provide valuable insights into GVHD occurring in the gastrointestinal tract, lung, and liver. With new insights designed to better predict and prevent GVHD and novel agents designed to treat GVHD, overcoming this current impediment to successful bone marrow transplantation should become increasingly feasible.

Heat shock proteins: to present or not, that is the question

The contribution of major histocompatibility complex (MHC) I and II to the adaptive immune response has been well documented. In 1996, Peter Doherty and Rolf Zinkernagel were awarded the Nobel Prize, for their fundamental observations concerning the genetic elements involved in specific antigen (Ag) recognition. These elements encode molecules that present self and non-self peptide fragments to both CD4+ and CD8+ cytolytic T lymphocytes (CTL). The recognition by Srivastava and coworkers that heat shock proteins (HSPs) might also present Ag in chemically induced sarcomas brought about many new questions concerning the central dogma of Ag processing and presentation. HSPs, in particular glucose-regulated peptide 94 (GRP94), HSP70 and to a lesser extent HSP90, bind peptides that are immunogenic in vitro and in vivo. There is mounting evidence that these HSP-peptide complexes provide alternative Ag-specific recognition in many systems. Whether a separate genetic program evolved in addition to MHC that increases the antigenic repertoire of the cell or if this newly observed function of HSP is predominantly a laboratory-based phenomena and/or a normal chaperone function of this family of proteins remains to be answered. Nevertheless, there are clinical therapeutic strategies that involve HSP-derived peptides isolated from various tumors that look extremely promising.

Proteomics applied to the clinical follow-up of patients after allogeneic hematopoietic stem cell transplantation

A phase 1 diagnostic study was performed to evaluate a novel technology for clinical proteomic research based on capillary electrophoresis and mass spectrometry. Urine from 40 patients after hematopoietic stem cell transplantation (HSCT; 35 allogeneic, 5 autologous) and 5 patients with sepsis was collected for a period of 100 days and analyzed. More than 1000 different polypeptides could be detected in individual samples. Polypeptide patterns excreted in the urine of patients were significantly different from those of healthy volunteers. No significant differences were detected comparing different conditioning regimens. The aim of this study was to identify polypeptide patterns functioning as early indicators of graft-versus-host disease (GVHD). Eighteen patients developed GVHD after allogeneic HSCT. Sixteen differentially excreted polypeptides formed a pattern of early GVHD markers, allowing discrimination of GVHD from patients without complications with 82% specificity and 100% sensitivity, cross-validated. Inclusion of 13 sepsis-specific polypeptides allowed us to distinguish sepsis from GVHD with a specificity of 97% and a sensitivity of 100%. Sequencing 2 prominent GVHD-indicative polypeptides led to the identification of a peptide from leukotriene A4 hydrolase and a peptide from serum albumin. The data reveal that capillary electrophoresis and mass spectrometry allow identification of biomarkers for a variety of diseases or related complications.

New Developments in Allotransplant Immunology

After allogeneic stem cell transplantation, the establishment of the donor’s immune system in an antigenically distinct recipient confers a therapeutic graft-versus-malignancy effect, but also causes graft-versus-host disease (GVHD) and protracted immune dysfunction. In the last decade, a molecular-level description of alloimmune interactions and the process of immune recovery leading to tolerance has emerged. Here, new developments in understanding alloresponses, genetic factors that modify them, and strategies to control immune reconstitution are described.

In Section I, Dr. John Barrett and colleagues describe the cellular and molecular basis of the alloresponse and the mechanisms underlying the three major outcomes of engraftment, GVHD and the graft-versus-leukemia (GVL) effect. Increasing knowledge of leukemia-restricted antigens suggests ways to separate GVHD and GVL. Recent findings highlight a central role of hematopoietic-derived antigen-presenting cells in the initiation of GVHD and distinct properties of natural killer (NK) cell alloreactivity in engraftment and GVL that are of therapeutic importance. Finally, a detailed map of cellular immune recovery post-transplant is emerging which highlights the importance of post-thymic lymphocytes in determining outcome in the critical first few months following stem cell transplantation. Factors that modify immune reconstitution include immunosuppression, GVHD, the cytokine milieu and poorly-defined homeostatic mechanisms which encourage irregular T cell expansions driven by immunodominant T cell–antigen interactions.

In Section II, Prof. Anne Dickinson and colleagues describe genetic polymorphisms outside the human leukocyte antigen (HLA) system that determine the nature of immune reconstitution after allogeneic stem cell transplantation (SCT) and thereby affect transplant outcomethrough GVHD, GVL, and transplant-related mortality. Polymorphisms in cytokine gene promotors and other less characterized genes affect the cytokine milieu of the recipient and the immune reactivity of the donor. Some cytokine gene polymorphisms are significantly associated with transplant outcome. Other non-HLA genes strongly affecting alloresponses code for minor histocompatibility antigens (mHA). Differences between donor and recipient mHA cause GVHD or GVL reactions or graft rejection. Both cytokine gene polymorphisms (CGP) and mHA differences resulting on donor-recipient incompatibilities can be jointly assessed in the skin explant assay as a functional way to select the most suitable donor or the best transplant approach for the recipient.

In Section III, Dr. Nelson Chao describes non-pharmaceutical techniques to control immune reconstitution post-transplant. T cells stimulated by host alloantigens can be distinguished from resting T cells by the expression of a variety of activation markers (IL-2 receptor, FAS, CD69, CD71) and by an increased photosensitivity to rhodamine dyes. These differences form the basis for eliminating GVHD-reactive T cells in vitro while conserving GVL and anti-viral immunity. Other attempts to control immune reactions post-transplant include the insertion of suicide genes into the transplanted T cells for effective termination of GVHD reactions, the removal of CD62 ligand expressing cells, and the modulation of T cell reactivity by favoring Th2, Tc2 lymphocyte subset expansion. These technologies could eliminate GVHD while preserving T cell responses to leukemia and reactivating viruses.