Development of Beta-Amyloid-Specific CAR-Tregs for the Treatment of Alzheimer's Disease.

BACKGROUND: Alzheimer's disease (AD) is a neurodegenerative disease that remains uncured. Its pathogenesis is characterized by the formation of ß-amyloid (Aß) plaques. The use of antigen-specific regulatory T cells (Tregs) through adoptive transfer has shown promise for the treatment of many inflammatory diseases, although the effectiveness of polyspecific Tregs is limited. Obtaining a sufficient number of antigen-specific Tregs from patients remains challenging. AIMS AND METHODS: To address this problem, we used an antibody-like single-chain variable fragment from a phage library and subsequently generated a chimeric antigen receptor (CAR) targeting ß-amyloid. RESULTS: The ß-amyloid-specific CARs obtained were stimulated by both recombinant and membrane-bound Aß isolated from the murine brain. The generated CAR-Tregs showed a normal Treg phenotype, were antigen-specific activatable, and had suppressive capacity. CONCLUSION: This study highlights the potential of CAR technology to generate antigen-specific Tregs and presents novel approaches for developing functional CARs.

Generation of Chimeric Antigen Receptors against Tetraspanin 7.

Adoptive transfer of antigen-specific regulatory T cells (Tregs) has shown promising results in the treatment of autoimmune diseases; however, the use of polyspecific Tregs has limited effects. However, obtaining a sufficient number of antigen-specific Tregs from patients with autoimmune disorders remains challenging. Chimeric antigen receptors (CARs) provide an alternative source of T cells for novel immunotherapies that redirect T cells independently of the MHC. In this study, we aimed to generate antibody-like single-chain variable fragments (scFv) and subsequent CARs against tetraspanin 7 (TSPAN7), a membrane protein highly expressed on the surface of pancreatic beta cells, using phage display technology. We established two methods for generating scFvs against TSPAN7 and other target structures. Moreover, we established novel assays to analyze and quantify their binding abilities. The resulting CARs were functional and activated specifically by the target structure, but could not recognize TSPAN7 on the surface of beta cells. Despite this, this study demonstrates that CAR technology is a powerful tool for generating antigen-specific T cells and provides new approaches for generating functional CARs.

PD-1/CTLA-4 Blockade Leads to Expansion of CD8+PD-1int TILs and Results in Tumor Remission in Experimental Liver Cancer.

Background: Checkpoint inhibitors act on exhausted CD8+ T cells and restore their effector function in chronic infections and cancer. The underlying mechanisms of action appear to differ between different types of cancer and are not yet fully understood. Methods: Here, we established a new orthotopic HCC model to study the effects of checkpoint blockade on exhausted CD8+ tumor-infiltrating lymphocytes (TILs). The tumors expressed endogenous levels of HA, which allowed the study of tumor-specific T cells. Results: The induced tumors developed an immune-resistant TME in which few T cells were found. The few recovered CD8+ TILs were mostly terminally exhausted and expressed high levels of PD-1. PD-1/CTLA-4 blockade resulted in a strong increase in the number of CD8+ TILs expressing intermediate amounts of PD-1, also called progenitor-exhausted CD8+ TILs, while terminally exhausted CD8+ TILs were almost absent in the tumors of treated mice. Although transferred naïve tumor-specific T cells did not expand in the tumors of untreated mice, they expanded strongly after treatment and generated progenitor-exhausted but not terminally exhausted CD8+ TILs. Unexpectedly, progenitor-exhausted CD8+ TILs mediated the antitumor response after treatment with minimal changes in their transcriptional profile. Conclusion: In our model, few doses of checkpoint inhibitors during the priming of transferred CD8+ tumor-specific T cells were sufficient to induce tumor remission. Therefore, PD-1/CTLA-4 blockade has an ameliorative effect on the expansion of recently primed CD8+ T cells while preventing their development into terminally exhausted CD8+ TILs in the TME. This finding could have important implications for future T-cell therapies.

Supraphysiological FOXP3 expression in human CAR-Tregs results in improved stability, efficacy, and safety of CAR-Treg products for clinical application.

The forkhead family transcription factor (FOXP3) is an essential regulator for the development of regulatory T cells (Tregs) and orchestrates both suppressive function and Treg lineage identity. Stable expression of FOXP3 enables Tregs to maintain immune homeostasis and prevent autoimmunity. However, under pro-inflammatory conditions, FOXP3 expression in Tregs can become unstable, leading to loss of suppressive function and conversion into pathogenic T effector cells. Therefore, the success of adoptive cell therapy with chimeric antigen receptor (CAR) Tregs is highly dependent on the stability of FOXP3 expression to ensure the safety of the cell product. To warrant the stable expression of FOXP3 in CAR-Treg products, we have developed an HLA-A2-specific CAR vector that co-expresses FOXP3. The transduction of isolated human Tregs with the FOXP3-CAR led to an increase in the safety and efficacy of the CAR-Treg product. In a hostile microenvironment, under pro-inflammatory and IL-2-deficient conditions, FOXP3-CAR-Tregs showed a stable expression of FOXP3 compared to Control-CAR-Tregs. Furthermore, additional exogenous expression of FOXP3 did not induce phenotypic alterations and dysfunctions such as cell exhaustion, loss of functional Treg characteristics or abnormal cytokine secretion. In a humanized mouse model, FOXP3-CAR-Tregs displayed an excellent ability to prevent allograft rejection. Furthermore, FOXP3-CAR-Tregs revealed coherent Treg niche-filling capabilities. Overexpression of FOXP3 in CAR-Tregs has thereby the potential to increase the efficacy and reliability of cellular products, promoting their clinical use in organ transplantation and autoimmune diseases.

Splenectomy induces biochemical remission and regeneration in experimental murine autoimmune hepatitis.

Autoimmune hepatitis (AIH) is a chronic immune-mediated inflammatory liver disease. It is known that AIH originates not from the spleen but from the liver itself. Nonetheless, most details of the etiology and pathophysiology are unknown. We induced experimental murine AIH (emAIH) in NOD/Ltj mice by single administration of a replication-deficient adenovirus and performed splenectomy during late-stage disease. Biochemical disease remission occurred, which was characterized by improvement in transaminase levels. The causes of this remission included a shift in the transcriptomic signature of serum proteins toward regeneration. At the cellular level, there was a marked decrease in activated CD8+ T cells and an increase in intrahepatic regulatory T cells (Tregs). Here, intrahepatic Treg numbers correlated with biochemical remission. Notably, an imbalance in the T-cell/B-cell ratio was observed, with a disproportionate increase in total B cells. In summary, intrahepatic increases in Tregs, biochemical remission, and regeneration could be induced by splenectomy in the late stage of emAIH.

The Detrimental Role of Regulatory T Cells in Nonalcoholic Steatohepatitis.

Nonalcoholic steatohepatitis (NASH) is induced by steatosis and metabolic inflammation. While involvement of the innate immune response has been shown, the role of the adaptive immune response in NASH remains controversial. Likewise, the role of regulatory T cells (Treg) in NASH remains unclear although initial clinical trials aim to target these regulatory responses. High-fat high-carbohydrate (HF-HC) diet feeding of NASH-resistant BALB/c mice as well as the corresponding recombination activating 1 (Rag)-deficient strain was used to induce NASH and to study the role of the adaptive immune response. HF-HC diet feeding induced strong activation of intrahepatic T cells in BALB/c mice, suggesting an antigen-driven effect. In contrast, the effects of the absence of the adaptive immune response was notable. NASH in BALB/c Rag1-/- mice was substantially worsened and accompanied by a sharp increase of M1-like macrophage numbers. Furthermore, we found an increase in intrahepatic Treg numbers in NASH, but either adoptive Treg transfer or anti-cluster of differentiation (CD)3 therapy unexpectedly increased steatosis and the alanine aminotransferase level without otherwise affecting NASH. Conclusion: Although intrahepatic T cells were activated and marginally clonally expanded in NASH, these effects were counterbalanced by increased Treg numbers. The ablation of adaptive immunity in murine NASH led to marked aggravation of NASH, suggesting that Tregs are not regulators of metabolic inflammation but rather enhance it.

Membrane-bound IL-2 improves the expansion, survival, and phenotype of CAR Tregs and confers resistance to calcineurin inhibitors.

Background: Regulatory T cells (Tregs) play an important role in the maintenance of immune homeostasis and the establishment of immune tolerance. Since Tregs do not secrete endogenous IL-2, they are especially dependent on external IL-2. IL-2 deficiency leads to lower Treg numbers, instability of the Treg phenotype and loss of immune regulation. After organ transplantation, patients are treated with calcineurin inhibitors (CNIs), which further limits available IL-2. Application of low-dose IL-2 expands Tregs but also activates NK and CD8+ T cells. It was recently shown that graft-specific Tregs recognizing mismatched MHC I molecules via a chimeric antigen receptor were far more potent than polyclonal Tregs in the regulation of immune responses after solid organ transplantation in a humanized mouse model. Methods: Therefore, our aim was to enhance the function and stability of transferred CAR-Tregs via expression of membrane-associated IL-2 (mbIL-2). Results: mbIL-2 promoted higher survival, phenotypic stability, and function among CAR-Tregs than observed in clinical trials. The cells were also more stable under inflammatory conditions. In a preclinical humanized mouse model, we demonstrated that mbIL-2 CAR Tregs survive better in the Treg niche than control CAR Tregs and are even resistant to CNI therapy without affecting other Tregs, thus acting mainly in cis. Discussion: The functional and phenotypic improvements observed after membrane-attached IL-2 expression in CAR-Tregs will be important step for enhancing CAR-Treg therapies currently being tested in clinical trials for use after kidney and liver transplantation as well as in autoimmune diseases.

Anti-CD20 Therapy Alters the Protein Signature in Experimental Murine AIH, but Not Exclusively towards Regeneration.

BACKGROUND: Autoimmune hepatitis (AIH) is a chronic autoimmune inflammatory disease that usually requires lifelong immunosuppression. Frequent recurrences after the discontinuation of therapy indicate that intrahepatic immune regulation is not restored by current treatments. Studies of other autoimmune diseases suggest that temporary depletion of B cells can improve disease progression in the long term. METHODS: We tested a single administration of anti-CD20 antibodies to reduce B cells and the amount of IgG to induce intrahepatic immune tolerance. We used our experimental murine AIH (emAIH) model and treated the mice with anti-CD20 during the late stage of the disease. RESULTS: After treatment, the mice showed the expected reductions in B cells and serum IgGs, but no improvements in pathology. However, all treated animals showed a highly altered serum protein expression pattern, which was a balance between inflammation and regeneration. CONCLUSIONS: In conclusion, anti-CD20 therapy did not produce clinically measurable results because it triggered inflammation, as well as regeneration, at the proteomic level. This finding suggests that anti-CD20 is ineffective as a sole treatment for AIH or emAIH.

Splenectomy Prior to Experimental Induction of Autoimmune Hepatitis Promotes More Severe Hepatic Inflammation, Production of IL-17 and Apoptosis.

Autoimmune hepatitis (AIH) is detected at a late stage in the course of the disease. Therefore, induction and etiology are largely unclear. It is controversial if the induction of autoimmunity occurs in the liver or in the spleen. In our experimental murine AIH model, the induction of autoimmunity did not occur in the spleen. Instead, a protective role of the spleen could be more likely. Therefore, we splenectomized mice followed by induction of experimental murine AIH. Splenectomized mice presented more severe portal inflammation. Furthermore, these mice had more IL-17, IL-23 receptor (IL-23R) and caspase 3 (casp3) and a decreased amount of erythropoietin in serum, while intrahepatic T cell compartments were unaffected. These results indicate that the spleen is not necessary for induction of AIH, and splenectomy disrupts the ability to immune regulate the intensity of hepatic inflammation, production of IL-17 and apoptosis.

Treg-specific IL-2 therapy can reestablish intrahepatic immune regulation in autoimmune hepatitis.

Autoimmune hepatitis (AIH) is a chronic autoimmune inflammatory disease that usually requires life-long immunosuppression. Frequent relapses after discontinuation of therapy indicate that intrahepatic immune regulation is not restored by current therapies. As steroid therapy preferentially depletes intrahepatic regulatory T cell (Tregs), immune regulation might be re-established by increasing and functionally strengthening intrahepatic Tregs. In recent clinical trials with low dose IL-2, the Treg compartment was strengthened in autoimmune diseases. Therefore, we tested complexed IL-2/anti-IL-2 to increase the selectivity for Tregs. We used our model of experimental murine AIH (emAIH) and treated the mice with complexed IL-2/anti-Il-2 in the late course of the disease. The mice showed increased intrahepatic and systemic Treg numbers after treatment and a reduction in activated, intrahepatic effector T cells (Teffs). This resulted in a reduction in liver-specific ALT levels and a molecular pattern similar to that of healthy individuals. In conclusion, complexed IL-2/anti-IL-2 restored the balance between Tregs and Teffs within the liver, thereby improving the course of emAIH. Treg-specific IL-2 augmentation offers new hope for reestablishing immune tolerance in patients with AIH.

Lipid nanoparticle-mediated siRNA delivery for safe targeting of human CML in vivo.

Efficient and safe delivery of siRNA in vivo is the biggest roadblock to clinical translation of RNA interference (RNAi)-based therapeutics. To date, lipid nanoparticles (LNPs) have shown efficient delivery of siRNA to the liver; however, delivery to other organs, especially hematopoietic tissues still remains a challenge. We developed DLin-MC3-DMA lipid-based LNP-siRNA formulations for systemic delivery against a driver oncogene to target human chronic myeloid leukemia (CML) cells in vivo. A microfluidic mixing technology was used to obtain reproducible ionizable cationic LNPs loaded with siRNA molecules targeting the BCR-ABL fusion oncogene found in CML. We show a highly efficient and non-toxic delivery of siRNA in vitro and in vivo with nearly 100% uptake of LNP-siRNA formulations in bone marrow of a leukemic model. By targeting the BCR-ABL fusion oncogene, we show a reduction of leukemic burden in our myeloid leukemia mouse model and demonstrate reduced disease burden in mice treated with LNP-BCR-ABL siRNA as compared with LNP-CTRL siRNA. Our study provides proof-of-principle that fusion oncogene specific RNAi therapeutics can be exploited against leukemic cells and promise novel treatment options for leukemia patients.

Transient increase of activated regulatory T cells early after kidney transplantation.

Regulatory T cells (Tregs) are crucial in controlling allospecific immune responses. However, studies in human kidney recipients regarding the contribution of polyspecific Tregs have provided differing results and studies on alloreactive Tregs are missing completely. In this retrospective study, we specifically analyzed activated CD4+CD25highFOXP3+GARP+ Tregs in 17 patients of a living donor kidney transplantation cohort longitudinally over 24 months by flow cytometry (FOXP3: forkhead box protein 3, GARP: glycoprotein A repetitions predominant). We could demonstrate that Tregs of patients with end-stage renal disease (ESRD) are already pre-activated when compared to healthy controls. Furthermore, even though total CD4+CD25highFOXP3+ Treg numbers decreased in the first three months after transplantation, frequency of activated Tregs increased significantly representing up to 40% of all peripheral Tregs. In a cohort of living donor kidney transplantation recipients with stable graft function, frequencies of activated Tregs did not correlate with the occurrence of acute cellular rejection or chronic graft dysfunction. Our results will be important for clinical trials using adoptive Treg therapy after kidney transplantation. Adoptively transferred Tregs could be important to compensate the Treg loss at month 3, while they have to compete within the Treg niche with a large number of activated Tregs.

Hepatic T Cell Tolerance Induction in An Inflammatory Environment.

For the development of autoimmune hepatitis (AIH), genetic predisposition and environmental triggers are of major importance. Although experimental AIH can be induced in genetically susceptible mice, the low precursor frequency of autoreactive T cells hampers a deeper analysis of liver-specific T cells. Here, we established a system where the model antigen hemagglutinin (HA) is expressed exclusively in hepatocytes of Rosa26-HA mice following administration of a replication deficient adenovirus expressing Cre recombinase (Ad-Cre). Under these conditions, hepatocytes mimic the generation of altered-self neoantigens. To follow autoreactive T cells during AIH, we adoptively transferred HA--specific Cl4-TCR and 6.5-TCR T cells into Ad-Cre infected -Rosa26-HA mice. Alternatively, Rosa26-HA mice have been crossed with TCR transgenic mice that were infected with Ad-Cre to break hepatic tolerance and induce the expression of the HA antigen as a hepatic self-antigen. Surprisingly, neither adoptive transfer nor a very high precursor frequency of autoreactive T cells was able to break tolerance in the context of adenoviral infection. The low proliferation of the antigen experienced autoreactive T cells despite the presence of the autoantigen and inflammation points to anergy as a potential tolerance mechanism. This model underscores the crucial importance of genetic susceptibility to break tolerance against hepatic autoantigens.

Hyperferritinemia and hypergammaglobulinemia predict the treatment response to standard therapy in autoimmune hepatitis.

Autoimmune hepatitis (AIH) is a chronic hepatitis with an increasing incidence. The majority of patients require life-long immunosuppression and incomplete treatment response is associated with a disease progression. An abnormal iron homeostasis or hyperferritinemia is associated with worse outcome in other chronic liver diseases and after liver transplantation. We assessed the capacity of baseline parameters including the iron status to predict the treatment response upon standard therapy in 109 patients with untreated AIH type 1 (AIH-1) in a retrospective single center study. Thereby, a hyperferritinemia (> 2.09 times upper limit of normal; Odds ratio (OR) = 8.82; 95% confidence interval (CI): 2.25-34.52) and lower immunoglobulins (<1.89 times upper limit of normal; OR = 6.78; CI: 1.87-24.59) at baseline were independently associated with the achievement of complete biochemical remission upon standard therapy. The predictive value increased when both variables were combined to a single treatment response score, when the cohort was randomly split into a training (area under the curve (AUC) = 0.749; CI 0.635-0.863) and internal validation cohort (AUC = 0.741; CI 0.558-0.924). Patients with a low treatment response score (<1) had significantly higher cumulative remission rates in the training (p<0.001) and the validation cohort (p = 0.024). The baseline hyperferritinemia was accompanied by a high serum iron, elevated transferrin saturations and mild hepatic iron depositions in the majority of patients. However, the abnormal iron status was quickly reversible under therapy. Mechanistically, the iron parameters were not stringently related to a hepatocellular damage. Ferritin rather seems deregulated from the master regulator hepcidin, which was down regulated, potentially mediated by the elevated hepatocyte growth factor. In conclusion, baseline levels of serum ferritin and immunoglobulins, which are part of the diagnostic work-up of AIH, can be used to predict the treatment response upon standard therapy in AIH-1, although confirmation from larger multicenter studies is pending.

The influence of genetic predisposition and autoimmune hepatitis inducing antigens in disease development.

Autoimmune hepatitis (AIH) is defined as a chronic liver inflammation with loss of tolerance against hepatocytes. The etiology and pathophysiology of AIH are still poorly understood because reliable animal models are limited. Therefore, we recently introduced a model of experimental murine AIH by a self-limited adenoviral infection with the AIH type 2 antigen formiminotransferase cyclodeaminase (FTCD). We could demonstrate that break of humoral tolerance towards liver specific autoantigens like FTCD and cytochrome P450 2D6 (CYP2D6) is not dependent on the genetic background. However, the development of AIH in autoantibody positive animals is determined by genetic background genes. We could also show that the break of humoral tolerance is necessary but not sufficient for the development of AIH. In contrast the break of tolerance against the ubiquitously expressed nuclear antigens (ANAs) is strictly dependent on genetic predisposition. Priming with the UGA suppressor tRNA-associated protein (soluble liver antigen; SLA) is a strong inducer of ANA reactivity, but not sufficient to cause AIH development thereby questioning the importance of anti-SLA immune response as an important driver in AIH. Monogenetic mutations such as Aire-deficiency can cause AIH in otherwise genetically resistant strains. CONCLUSION: The results have important implications for our understanding of the pathophysiology of AIH development and for the interpretation of humoral antibody responses in AIH.

Ribonuclease (RNase) Prolongs Survival of Grafts in Experimental Heart Transplantation.

BACKGROUND: Cell damage, tissue and vascular injury are associated with the exposure and release of intracellular components such as RNA, which promote inflammatory reactions and thrombosis. Based on the counteracting anti-inflammatory and cardioprotective functions of ribonuclease A (RNase A) in this context, its role in an experimental model of heart transplantation in rats was studied. METHODS AND RESULTS: Inbred BN/OrlRj rat cardiac allografts were heterotopically transplanted into inbred LEW/OrlRj rats. Recipients were intravenously treated every other day with saline or bovine pancreatic RNase A (50 µg/kg). Toxic side effects were not found (macroscopically and histologically). Heart tissue flow cytometry and quantitative morphological analyses of explanted hearts at postoperative day 1 or postoperative day 4 showed reduced leukocyte infiltration, edema, and thrombus formation in RNase A-treated rats. In allogeneic mixed lymphocyte reactions, RNase A decreased the proliferation of effector T cells. RNase A treatment of rats resulted in prolonged median graft survival up to 10.5 days (interquartile range 1.8) compared to 6.5 days (interquartile range 1.0) in saline treatment (P=0.001). Treatment of rats with a new generated (recombinant) human pancreatic RNase 1 prolonged median graft survival similarly, unlike treatment with (recombinant) inactive human RNase 1 (each 50 µg/kg IV every other day, 11.0 days, interquartile range 0.3, versus 8.0 days, interquartile range 0.5, P=0.007). CONCLUSIONS: Upon heart transplantation, RNase administration appears to present a promising and safe drug to counteract ischemia/reperfusion injury and graft rejection. Furthermore, RNase treatment may be considered in situations of critical reperfusion after percutaneous coronary interventions or in cardiac surgery using the heart-lung machine.

Preferential accumulation of T helper cells but not cytotoxic T cells characterizes benign subclinical rejection of human liver allografts.

Subclinical rejection (SCR) is a common event in protocol biopsies after liver transplantation (LT). So far the interpretation of the underlying histological changes and clinical significance is limited. Previous studies were restricted to SCR manifestations within the first weeks after transplantation with limited follow-up. We analyzed clinical data from our prospective protocol biopsy program and found late SCR (at least 3 months after transplantation) to be a common event (41/94 patients). SCR manifested much later than acute cellular rejection (ACR). In the second year after transplantation, the SCR incidence in protocol biopsies reached a plateau of approximately 25% and remained at this level until the latest observed manifestations more than 5 years after transplantation. During a median follow-up of 32 months after SCR, no acute or chronic rejection, relevant graft fibrosis, graft loss, or liver-related death occurred even without specific therapy for SCR. Immunophenotyping of liver biopsies during SCR showed that similar to ACR, the composition of intrahepatic T cells depended on the severity of histological rejection. However, SCR showed a different pattern of infiltrating T cells with a stronger accumulation of CD4(+) cells, an increasing CD4(+) /CD8(+) ratio, and an increasing CD4(+) forkhead box P3 (FOXP3)(+) regulatory T cell (Treg)/CD8(+) ratio, which was not seen in ACR. These intrahepatic T cell patterns were not reflected in the peripheral blood. In conclusion, late SCR after LT has a good clinical prognosis, and it seems safe to leave it untreated. This benign clinical course compared to ACR is associated with intrahepatic T cell infiltration patterns showing less cytotoxic T cells and more CD4(+) FOXP3(+) Tregs. Liver Transplantation 22 943-955 2016 AASLD.

Autoimmune hepatitis in a murine autoimmune polyendocrine syndrome type 1 model is directed against multiple autoantigens.

UNLABELLED: Autoimmune polyendocrine syndrome type 1 (APS-1) is caused by mutations of the autoimmune regulator (AIRE) gene. Mouse studies have shown that this results in defective negative selection of T cells and defective early seeding of peripheral organs with regulatory T cells (Tregs). Aire deficiency in humans and mice manifests as spontaneous autoimmunity against multiple organs, and 20% of patients develop an autoimmune hepatitis (AIH). To study AIH in APS-1, we generated a murine model of human AIH on a BALB/c mouse background, in which Aire is truncated at exon 2. A subgroup of 24% of mice is affected by AIH, characterized by lymphoplasmacytic and periportal hepatic infiltrates, autoantibodies, elevated aminotransferases, and a chronic and progressive course of disease. Disease manifestation was dependent on specific Aire mutations and the genetic background of the mice. Though intrahepatic Treg numbers were increased and hyperproliferative, the intrahepatic CD4/CD8 ratio was decreased. The targets of the adaptive autoimmune response were polyspecific and not focussed on essential autoantigens, as described for other APS-1-related autoimmune diseases. The AIH could be treated with prednisolone or adoptive transfer of polyspecific Tregs. CONCLUSION: Development of AIH in APS-1 is dependent on specific Aire mutations and genetic background genes. Autoimmune response is polyspecific and can be controlled by steroids or transfer with Tregs. This might enable new treatment options for patients with AIH.