Driving allotolerance: CAR-expressing Tregs for tolerance induction in organ and stem cell transplantation

Regulatory T cells (Tregs) modulate the function of a variety of immune cells and are critical for maintaining self-tolerance and preventing the development of autoimmune disease. Due to their ability to suppress effector T cells, Tregs have been increasingly explored for clinical use to suppress alloresponses. While this approach has been promising in preclinical models and early clinical trials, widespread clinical use of Tregs has been limited by the low number of these cells in the periphery and the unknown frequency of allo-responsive Tregs. In this issue of the JCI, MacDonald and colleagues transduced human Tregs with a chimeric antigen receptor (CAR) that targets the HLA class I molecule A2. These CAR-expressing T cells were readily activated via CAR stimulation and exerted potent immunosuppressive effects when stimulated in vitro. In a murine model of hematopoietic stem cell transplantation, CAR-modified Tregs were more effective in preventing the development of graft-versus-host disease compared with polyclonal Tregs. The results of this study lay the groundwork for the further evaluation of CAR-expressing Tregs in the prevention or treatment of transplant complications.

Impact of unbalanced minor route versus major route karyotypes at diagnosis on prognosis of CML

Major route additional cytogenetic aberrations (ACA) at diagnosis of chronic myeloid leukaemia (CML) indicate an increased risk of progression and shorter survival. Since major route ACA are almost always unbalanced, it is unclear whether other unbalanced ACA at diagnosis also confer an unfavourable prognosis. On the basis of 1348 Philadelphia chromosome-positive chronic phase patients of the randomized CML study IV, we examined the impact of unbalanced minor route ACA at diagnosis versus major route ACA on prognosis. At diagnosis, 1175 patients (87.2 %) had a translocation t(9;22)(q34;q11) and 74 (5.5 %) a variant translocation t(v;22) only, while a loss of the Y chromosome (-Y) was present in addition in 44 (3.3 %), balanced or unbalanced minor route ACA each in 17 (1.3 %) and major route ACA in 21 (1.6 %) cases. Patients with unbalanced minor route ACA had no significantly different cumulative incidences of complete cytogenetic remission or major molecular remission and no significantly different progression-free survival (PFS) or overall survival (OS) than patients with t(9;22), t(v;22), -Y and balanced minor route karyotypes. In contrast, patients with major route ACA had a shorter OS and PFS than all other groups (all pairwise comparisons to each of the other groups: p ≤ 0.015). Five-year survival probabilities were for t(9;22) 91.4 % (95 % CI 89.5-93.1), t(v; 22) 87 % (77.2-94.3), -Y 89.0 % (76.7-97.0), balanced 100 %, unbalanced minor route 92.3 % (72.4-100) and major route 52.2 % (28.2-75.5). We conclude that only major route, but not balanced or unbalanced minor route ACA at diagnosis, has a negative impact on prognosis of CML.

Total nodal irradiation in patients with severe treatment-refractory chronic graft-versus-host disease after allogeneic stem cell transplantation: Response rates and immunomodulatory effects

BACKGROUND AND PURPOSE

The use of total nodal irradiation (TNI) has been reported as an immunomodulatory therapy for different diseases including chronic graft-versus-host disease (cGVHD).

MATERIAL AND METHODS

We retrospectively analyzed 13 patients with treatment-refractory cGVHD receiving TNI with 1×1Gy from 2001 to 2014. In 10 of 13 patients immunomodulatory effects of TNI were measured.

RESULTS

At time of TNI all patients had severe cGVHD (involving the skin: n=12), fascia (n=6), oral mucosa (n=8), eye (n=8), and lung (n=5). Nine of 13 patients had corticosteroid-refractory cGVHD. In 7 of 13 patients (54%) a partial response (PR) could be achieved. In 3 patients (23%) cGVHD manifestations remained stable, 2 patients progressed. One patient was not evaluable due to follow-up <1 month. At 3 months after TNI, best responses could be achieved in skin, and oral involvement including steroid sparing activity. TNI was well tolerated with adverse effects limited to reversible thrombocytopenia and neutropenia. Immunomodulatory effects on peripheral blood cells could be demonstrated including an increase of CD4+ T cells in the group of responders.

CONCLUSIONS

TNI represents an effective immunomodulating therapy in treatment-refractory cGVHD.

Basophils inhibit proliferation of CD4⁺ T cells in autologous and allogeneic mixed lymphocyte reactions and limit disease activity in a murine model of graft versus host disease

Basophils are known to modulate the phenotype of CD4(+) T cells and to enhance T helper type 2 responses in vitro and in vivo. In this study, we demonstrate that murine basophils inhibit proliferation of CD4(+) T cells in autologous and allogeneic mixed lymphocyte reactions. The inhibition is independent of Fas and MHC class II, but dependent on activation of basophils with subsequent release of interleukin-4 (IL-4) and IL-6. The inhibitory effect of basophils on T-cell proliferation can be blocked with antibodies against IL-4 and IL-6 and is absent in IL-4/IL-6 double-deficient mice. In addition, we show that basophils and IL-4 have beneficial effects on disease activity in a murine model of acute graft-versus-host disease (GvHD). When basophils were depleted with the antibody MAR-1 before induction of GvHD, weight loss, GvHD score, mortality and plasma tumour necrosis factor levels were increased while injection of IL-4 improved GvHD. Basophil-depleted mice with GvHD also have increased numbers of CD4(+) T cells in the mesenteric lymph nodes. Our data show for the first time that basophils suppress autologous and allogeneic CD4(+) T-cell proliferation in an IL-4-dependent manner.

Identification and characterization of the specific murine NK cell subset supporting graft-versus-leukemia- and reducing graft-versus-host-effects

Clinical studies investigating the impact of natural killer (NK) cells in allogeneic hematopoietic stem cell transplantation settings have yielded promising results. However, NK cells are a functionally and phenotypically heterogeneous population. Therefore, we addressed the functional relevance of specific NK cell subsets distinguished by expression of CD117, CD27 and CD11b surface markers in graft-versus-leukemia (GVL)-reaction and graft-versus-host-disease (GVHD). Our results clearly demonstrate that the subset of c-Kit⁻CD27⁻CD11b⁺ NK cells expressed multiple cytotoxic pathway genes and provided optimal graft-versus-leukemia-effects, while significantly reducing T cell proliferation induced by allogeneic dendritic cells. Furthermore, these NK cells migrated to inflamed intestinal tissues where graft-versus-host-colitis was efficiently mitigated. For the first time, we identified the c-Kit⁻CD27⁻CD11b⁺ NK cell population as the specific effector NK cell subset capable of significantly diminishing GVHD in fully mismatched bone marrow transplantation settings. In conclusion, the subset of c-Kit⁻CD27⁻CD11b⁺ NK cells not only supports GVL, but also plays a unique role in the protection against GVHD by migrating to the peripheral GVHD target organs where they exert efficient immunoregulatory activities. These new insights demonstrate the importance of selecting the optimal NK cell subset for cellular immunotherapy following allogeneic hematopoietic stem cell transplantation.

CD19+CD21low B cells and CD4+CD45RA+CD31+ T cells correlate with first diagnosis of chronic graft-versus-host disease

Chronic graft-versus-host disease (cGVHD) is a serious and frequent complication of allogeneic hematopoietic stem cell transplantation (HCT). Currently, no biomarkers for prediction and diagnosis of cGVHD are available. We performed a large prospective study focusing on noninvasive biomarkers for National Institutes of Health-defined cGVHD patients (n = 163) in comparison to time-matched HCT recipients who never experienced cGVHD (n = 64), analyzed from day 100 after HCT. In logistic regression analysis, CD19(+)CD21(low) B cells (P = .002; hazard ratio [HR], 3.31; 95% confidence interval [CI], 1.53 to 7.17) and CD4(+)CD45RA(+)CD31(+) T cells (P < .001; HR, 3.88; 95% CI, 1.88 to 7.99) assessed on day 100 after HCT were significantly associated with subsequent development of cGVHD, independent of clinical parameters. A significant association with diagnosis of cGVHD was only observed for CD19(+)CD21(low) B cells (P = .008; HR, 3.00; 95% CI, 1.33 to 6.75) and CD4(+)CD45RA(+)CD31(+) T cells (P = .017; HR, 2.80; 95% CI, 1.19 to 6.55). CD19(+)CD21(low) B cells were found to have the highest discriminatory value with an area under the receiver operating curve of .77 (95% CI, .64 to .90). Our results demonstrate that CD19(+)CD21(low) B cells and CD4(+)CD45RA(+)CD31(+) T cells are significantly elevated in patients with newly diagnosed cGVHD.

The impact of a tumor diagnosis on patients' attitudes toward advance directives

BACKGROUND

Although advance care planning and the completion of advance directives (ADs) are important tools to avoid unwanted aggressive care once patients have lost their decision-making capacity, only a minority of cancer patients are admitted with completed ADs, and little is known about patients' wishes regarding AD consultations.

METHODS

For 1 year, every new patient admitted to the hematology/oncology outpatient clinic of the University Hospital Regensburg received a self-administered questionnaire comprising a self-evaluation of AD knowledge and questions about preferences regarding consultation partners and the time of consultation. Disease-related data were collected from medical records. Statistics were calculated with SPSS.

RESULTS

Of the 500 questionnaires handed out, 394 (75%) were evaluable and analyzed. Twenty-eight percent of the participants had completed an AD (living will or health care proxy). Ninety-two percent of the participants without ADs had never received a consultation offer from any professional involved. Only 20% perceived a clear relation between cancer and AD consultations. More than 50% of the participants without ADs were in favor of consultations 'now' or 'in a few weeks', while more than 40% objected to AD consultations.

CONCLUSIONS

Oncology patients have a large unmet demand for AD consultations. However, a relevant percentage of these patients object to AD consultations. Structured and early AD consultation offers should be made, and early discussions about indications for aggressive treatment should take place.

Metagenomic analysis of the stool microbiome in patients receiving allogeneic stem cell transplantation: loss of diversity is associated with use of systemic antibiotics and more pronounced in gastrointestinal graft-versus-host disease

Next-generation sequencing of the hypervariable V3 region of the 16s rRNA gene isolated from serial stool specimens collected from 31 patients receiving allogeneic stem cell transplantation (SCT) was performed to elucidate variations in the composition of the intestinal microbiome in the course of allogeneic SCT. Metagenomic analysis was complemented by strain-specific enterococcal PCR and indirect assessment of bacterial load by liquid chromatography-tandem mass spectrometry of urinary indoxyl sulfate. At the time of admission, patients showed a predominance of commensal bacteria. After transplantation, a relative shift toward enterococci was observed, which was more pronounced under antibiotic prophylaxis and treatment of neutropenic infections. The shift was particularly prominent in patients that developed subsequently or suffered from active gastrointestinal (GI) graft-versus-host disease (GVHD). The mean proportion of enterococci in post-transplant stool specimens was 21% in patients who did not develop GI GVHD as compared with 46% in those that subsequently developed GI GVHD and 74% at the time of active GVHD. Enterococcal PCR confirmed predominance of Enterococcus faecium or both E. faecium and Enterococcus faecalis in these specimens. As a consequence of the loss of bacterial diversity, mean urinary indoxyl sulfate levels dropped from 42.5 ± 11 μmol/L to 11.8 ± 2.8 μmol/L in all post-transplant samples and to 3.5 ± 3 μmol/L in samples from patients with active GVHD. Our study reveals major microbiome shifts in the course of allogeneic SCT that occur in the period of antibiotic treatment but are more prominent in association with GI GVHD. Our data indicate early microbiome shifts and a loss of diversity of the intestinal microbiome that may affect intestinal inflammation in the setting of allogeneic SCT.

TLR5 stop codon polymorphism is associated with invasive aspergillosis after allogeneic stem cell transplantation

Single nucleotide polymorphisms (SNPs) have been associated with an increased incidence of invasive aspergillosis (IA) after allogeneic stem cell transplantation (allo-SCT). We analyzed 41 patients with proven/probable IA after allo-SCT for an association of SNPs, within the TLR2, TLR4, TLR5, TLR9, and NOD2/CARD15 genes, with susceptibility to IA. The control group consisted of 130 patients who had allo-SCT but did not develop IA. While no association was found for donor SNPs and the recipients' risk of IA, analysis of recipient SNPs showed a significant association between the presence of recipient TLR5-Stop SNP (1174C> T) and the incidence of IA (P = 0.004). Multivariate analysis demonstrated that the recipient TLR5-Stop SNP appeared as an independent risk factor for IA after allo-SCT. Our study suggests that TLR5 is involved in host defense against Aspergillus fumigatus, and that the recipient TLR5-Stop SNP represents a risk factor for the development of IA after allo-SCT.

Dominant Th2 differentiation of human regulatory T cells upon loss of FOXP3 expression

CD4(+)CD25(+)FOXP3(+) regulatory T cells (Treg) are pivotal for peripheral self-tolerance. They prevent immune responses to auto- and alloantigens and are thus under close scrutiny as cellular therapeutics for autoimmune diseases and the prevention or treatment of alloresponses after organ or stem cell transplantation. We previously showed that human Treg with a memory cell phenotype, but not those with a naive phenotype, rapidly downregulate expression of the lineage-defining transcription factor FOXP3 upon in vitro expansion. We now compared the transcriptomes of stable FOXP3(+) Treg and converted FOXP3(-) ex-Treg by applying a newly developed intranuclear staining protocol that permits the isolation of intact mRNA from fixed, permeabilized, and FACS-purified cell populations. Whole-genome microarray analysis revealed strong and selective upregulation of Th2 signature genes, including GATA-3, IL-4, IL-5, and IL-13, upon downregulation of FOXP3. Th2 differentiation of converted FOXP3(-) ex-Treg occurred even under nonpolarizing conditions and could not be prevented by IL-4 signaling blockade. Thus, our studies identify Th2 differentiation as the default developmental program of human Treg after downregulation of FOXP3.

The lack of memory B cells including T cell independent IgM+ IgD+ memory B cells in chronic graft-versus host disease is associated with susceptibility to infection

The chronic graft-versus host disease (cGVHD) is associated with a perturbed B cell homeostasis and an increased infection rate. Aiming to determine the impact of lymphocyte subsets on cGVHD, blood samples from 98 patients at least 100 days following allogeneic haematopoietic stem cell transplantation (median 1066 days) were analyzed, serum levels of immunoglobulins measured and the incidence of severe infections retrospectively documented. Absolute CD19(+) B cell counts, including counts of immature (CD10(+) CD38(++) CD20(+) IgM(++)) and transitional (CD10(-) CD38(++) CD20(+) IgM(++)) as well as class switched memory (CD19(+) CD27(+) IgM(-) IgD(-)) B cells in patients with active cGVHD (n = 52) were significantly decreased as compared to those with inactive (n = 18) or without cGVHD (n = 28). In addition, nonclass switched IgM(+) memory B cells (CD19(+) CD27(+) IgM(+) IgD(+)) were absent in patients with cGVHD, but not in patients with inactive (0.4 × 10(6) /l) or without (1.7 × 10(6) /l) cGVHD (both P < 0.001). In line with these results we found significantly decreased lgG levels in patients with cGVHD, which was associated with a significantly higher rate of severe infections in cGVHD patients. Our data underline the close association of diminished B cell counts with cGVHD and the onset of severe infections. The lack of IgM(+) memory B cells in patients with cGVHD may indicate functional asplenia.

Vaccination against pandemic H1N1 (2009) in patients after allogeneic hematopoietic stem cell transplantation: a retrospective analysis

Purpose

Limited data are available on immunologic responses to primary pandemic H1N1 (2009) vaccination in recipients of allogeneic hematopoietic stem cell transplantation (HSCT) recipients. In 2009 serologic responses to either pandemic H1N1 (2009) vaccine (n = 36) or pandemic H1N1 (2009) infection (n = 2) were studied in 38 HSCT recipients.

Methods

Responses were measured with a standard hemagglutination-inhibition assay. Fourteen patients had active chronic graft-versus-host disease (cGvHD) at the time of vaccination/infection and seven patients had cGvHD in remission; 11 patients had no immunosuppressive therapy, and 27 patients were on immunosuppressive therapy. Nineteen patients (53%) responded to pandemic H1N1 (2009) vaccination. Two patients had pandemic H1N1 (2009) infection without prior vaccination, and one patient had severe pandemic H1N1 (2009) infection with acute respiratory distress syndrome despite prior single vaccination.

Results

Non-responders to pandemic H1N1 (2009) vaccination more often had cGvHD (65 vs. 53%) and received second- or third-line therapy (53 vs. 11%), while responders mostly had first-line therapy for cGvHD. While vaccine responders had no or single agent immunosuppressive therapy, non-responders frequently received moderate or intense immunosuppressive therapy. All vaccine recipients previously treated with rituximab were non-responders.

Conclusions

In summary, the overall response to pandemic H1N1 (2009) vaccination in HSCT recipients was modest. Patients receiving combined immunosuppressive therapy for steroid-refractory cGvHD barely responded to pandemic H1N1 (2009) vaccination.

Regulatory T cells in stem cell transplantation: strategies and first clinical experiences

The adoptive transfer of donor-type CD4(+)CD25(+)FOXP3(+) regulatory T cells (Treg) protects from graft-versus-host disease in murine bone marrow transplantation models. Results from first clinical trials exploring such strategies have recently been presented and seem to confirm the efficacy of Treg for the prevention of this severe complication after allogeneic stem cell transplantation. Further improvements in Treg isolation and in vitro expansion technologies will facilitate the broader exploration of Treg therapies, for example, for the treatment of ongoing graft-versus-host disease or the prevention of graft rejection after solid organ transplantation.

Epigenetic reprogramming of the RORC locus during in vitro expansion is a distinctive feature of human memory but not naïve Treg

The adoptive transfer of in vitro expanded Treg is a promising treatment option for autoimmune as well as alloantigen-induced diseases. Yet, concerns about the phenotypic and functional stability of Tregs upon in vitro culture command both careful selection of the starting population and thorough characterization of the final cell product. Recently, a high degree of developmental plasticity has been described for murine Treg and Th17 cells. Similarly, IL-17-producing FOXP3(+) cells have been detected among the CD45RA(-) memory-type subpopulation of human Tregs ex vivo. This prompted us to investigate the predisposition of human naïve and memory Tregs to develop into Th17 cells during polyclonal in vitro expansion. Here, we show that stimulation-induced DNA demethylation of RORC, which encodes the lineage-defining transcription factor for Th17 cells, occurs selectively in CD45RA(-) memory-type Tregs, irrespective of their FOXP3 expression level. On the contrary, naïve CD45RA(+) Tregs retain stable CpG methylation across the RORC locus even upon prolonged ex vivo expansion and in consequence show only a marginal tendency to express RORC and develop into IL-17-producing cells. These findings are highly relevant for the generation of therapeutic Treg products.

Polyclonal expansion of human CD4(+)CD25(+) regulatory T cells

Based on results from experimental animal models, the adoptive transfer of CD4(+)CD25(+)FOXP3(+) regulatory T cells (Treg) is expected to be efficacious in treating autoimmune and inflammatory diseases, as well as in preventing alloresponses after solid organ or stem-cell transplantation. For potential clinical applications, large numbers of Treg cells in maximum purity will be required to avoid the risk of disease exacerbation by contaminating effector T cells. We have recently described methods for the efficient in vitro expansion of human Treg cells and identified CD4(+)CD25(high)CD45RA(+) T cells as the ideal starting population for the generation of homogeneous and stable Treg cell products. Here, we provide detailed instructions for their identification, isolation, expansion, and functional characterization.

Recipient NOD2/CARD15 status affects cellular infiltrates in human intestinal graft-versus-host disease

Nucleotide-binding oligomerization domain 2/caspase recruitment domain 15 (NOD2/CARD15) polymorphisms have been identified as risk factors of both Crohn's disease and graft-versus-host disease (GVHD) following allogeneic stem cell transplantation. However, the role of these receptors of innate immunity in the pathophysiology of gastrointestinal GVHD is still poorly defined. Immunohistological features of intestinal GVHD were analysed in gastrointestinal biopsies from 58 patients obtained at the time of first onset of intestinal symptoms. The observed changes were correlated with concomitant risk factors and the presence of polymorphisms within the pathogen recognition receptor gene NOD2/CARD15. Intestinal GVHD was associated with a stage-dependent decrease in CD4 T cell infiltrates and an increase in CD8 T cells in the lamina propria; CD8 infiltrates correlated with extent of apoptosis and consecutive epithelial proliferation. The presence of NOD2/CARD15 variants in the recipient was associated with a significant loss of CD4 T cells: in a semiquantitative analysis, the median CD4 score for patients with wild-type NOD2/CARD15 was 1.1 (range 3), but only 0.4 (range 2) for patients with variants (P = 0.002). This observation was independent from severity of GVHD in multivariate analyses and could not be explained by the loss of forkhead box P3(+) T cells. Our results suggest a loss of protective CD4 T cells in intestinal GVHD which is enhanced further by the presence of NOD2/CARD15 variants. Our study might help to identify more selective therapeutic strategies in the future.

Pharmaceutical and cellular strategies in prophylaxis and treatment of graft-versus-host disease

Acute and chronic GVHD after allogeneic hematopoetic stem cell transplantation are still associated with significant morbidity and mortality. For prophylaxis of acute GVHD calcineurin inhibitors in combination with an antimetabolite (MTX or MMF) are administered, and these therapies are based on controlled studies. New prophylaxis strategies include mTOR-inhibitors in combination with tacrolimus but require confirmation by controlled trials. First-line treatment of acute GVHD consists mainly of steroids with doses ranging from 1 mg/kg/day prednisone to 3 mg/kg/day methylprednisolone. Second-line treatment of acute GVHD after failure of steroids is less well defined due to the lack of controlled studies. Treatment options are the use of cytotoxic antibodies (ATG, campath), cytokine blocking agents (etanercept, daclizumab), immunomodulating modalities (photopheresis), and antimetabolites (pentostatin, MMF). Recently, cellular approaches were developed, such as the adoptive transfer of mesenchymal stem cells. Nevertheless steroid-resistant acute GVHD is still a main challenge in alloHSCT and associated with high mortality. First-line treatment of chronic GVHD is also based on steroids with 1 mg/kg/day prednisolone or prednisone, which are often combined with calcineurin inhibitors. There is no consensus on second-line treatment of chronic GVHD and most therapies are solely based on phase II trials. Treatment options are the use of immunomodulating modalities (photopheresis, mTOR-inhibitors) and antimetabolites (MMF, MTX, pentostatin). Recent reports showed an efficacy of rituximab in selected patients. Other treatment options are low dose total nodal irradiation or the use of antibodies like ATG. Moreover, successful topical treatment of manifestations of chronic GVHD manifestations has been reported consisting of topical steroids like budesonide, topical calcineurin inhibitors, or PUVA.

Lineage-specific DNA methylation in T cells correlates with histone methylation and enhancer activity

DNA methylation participates in establishing and maintaining chromatin structures and regulates gene transcription during mammalian development and cellular differentiation. With few exceptions, research thus far has focused on gene promoters, and little is known about the extent, functional relevance, and regulation of cell type-specific DNA methylation at promoter-distal sites. Here, we present a comprehensive analysis of differential DNA methylation in human conventional CD4(+) T cells (Tconv) and CD4(+)CD25(+) regulatory T cells (Treg), cell types whose differentiation and function are known to be controlled by epigenetic mechanisms. Using a novel approach that is based on the separation of a genome into methylated and unmethylated fractions, we examined the extent of lineage-specific DNA methylation across whole gene loci. More than 100 differentially methylated regions (DMRs) were identified that are present mainly in cell type-specific genes (e.g., FOXP3, IL2RA, CTLA4, CD40LG, and IFNG) and show differential patterns of histone H3 lysine 4 methylation. Interestingly, the majority of DMRs were located at promoter-distal sites, and many of these areas harbor DNA methylation-dependent enhancer activity in reporter gene assays. Thus, our study provides a comprehensive, locus-wide analysis of lineage-specific methylation patterns in Treg and Tconv cells, links cell type-specific DNA methylation with histone methylation and regulatory function, and identifies a number of cell type-specific, CpG methylation-sensitive enhancers in immunologically relevant genes.