Elmar Jaeckel

Early monotherapy with pegylated interferon alpha-2b for acute hepatitis C infection: the HEP-NET acute-HCV-II study

Early treatment of acute hepatitis C with interferon alpha‐2b for 24 weeks prevents chronic infection in almost all patients. Because pegylated interferons have replaced conventional interferon in the therapy of chronic hepatitis C, the aim of this study was to analyze the efficacy of an early treatment of acute hepatitis C with peginterferon alfa‐ 2b. Between February 2001 and February 2004, 89 individuals with acute HCV infection were recruited at 53 different centers in Germany. Patients received 1.5 μg/kg peginterferon alfa‐2b for 24 weeks; treatment was initiated after a median of 76 days after infection (range 14‐150). End‐of‐treatment response and sustained virological response were defined as undetectable HCV RNA at the end of therapy and after 24 weeks of follow‐up, respectively. In the total study population, virological response was 82% at the end of treatment and 71% at the end of follow‐up. Of 89 individuals, 65 (73%) were adherent to therapy, receiving 80% of the interferon dosage within 80% of the scheduled treatment duration. End‐of‐treatment and sustained virological response rates in this subpopulation were 94% and 89%, respectively. A maximum alanine aminotransferase level of more than 500 U/L prior to therapy was the only factor associated with successful treatment. In conclusion, in acute HCV infection, early treatment with peginterferon α2b leads to high virological response rates in individuals who are adherent to treatment. The high number of dropouts underlines the importance of thorough patient selection and close monitoring during therapy. Thus, future studies should identify factors predicting spontaneous viral clearance to avoid unnecessary therapy. (HEPATOLOGY 2006;43:250–256.)

Intra-graft expression of genes involved in iron homeostasis predicts the development of operational tolerance in human liver transplantation.

Following organ transplantation, lifelong immunosuppressive therapy is required to prevent the host immune system from destroying the allograft. This can cause severe side effects and increased recipient morbidity and mortality. Complete cessation of immunosuppressive drugs has been successfully accomplished in selected transplant recipients, providing proof of principle that operational allograft tolerance is attainable in clinical transplantation. The intra-graft molecular pathways associated with successful drug withdrawal, however, are not well defined. In this study, we analyzed sequential blood and liver tissue samples collected from liver transplant recipients enrolled in a prospective multicenter immunosuppressive drug withdrawal clinical trial. Before initiation of drug withdrawal, operationally tolerant and non-tolerant recipients differed in the intra-graft expression of genes involved in the regulation of iron homeostasis. Furthermore, as compared with non-tolerant recipients, operationally tolerant patients exhibited higher serum levels of hepcidin and ferritin and increased hepatocyte iron deposition. Finally, liver tissue gene expression measurements accurately predicted the outcome of immunosuppressive withdrawal in an independent set of patients. These results point to a critical role for iron metabolism in the regulation of intra-graft alloimmune responses in humans and provide a set of biomarkers to conduct drug-weaning trials in liver transplantation.

Treg‐Therapy Allows Mixed Chimerism and Transplantation Tolerance Without Cytoreductive Conditioning

Establishment of mixed chimerism through transplantation of allogeneic donor bone marrow (BM) into sufficiently conditioned recipients is an effective experimental approach for the induction of transplantation tolerance. Clinical translation, however, is impeded by the lack of feasible protocols devoid of cytoreductive conditioning (i.e. irradiation and cytotoxic drugs/mAbs). The therapeutic application of regulatory T cells (Tregs) prolongs allograft survival in experimental models, but appears insufficient to induce robust tolerance on its own. We thus investigated whether mixed chimerism and tolerance could be realized without the need for cytoreductive treatment by combining Treg therapy with BM transplantation (BMT). Polyclonal recipient Tregs were cotransplanted with a moderate dose of fully mismatched allogeneic donor BM into recipients conditioned solely with short‐course costimulation blockade and rapamycin. This combination treatment led to long‐term multilineage chimerism and donor‐specific skin graft tolerance. Chimeras also developed humoral and in vitro tolerance. Both deletional and nondeletional mechanisms contributed to maintenance of tolerance. All tested populations of polyclonal Tregs (FoxP3‐transduced Tregs, natural Tregs and TGF‐β induced Tregs) were effective in this setting. Thus, Treg therapy achieves mixed chimerism and tolerance without cytoreductive recipient treatment, thereby eliminating a major toxic element impeding clinical translation of this approach.

Making regulatory T cells with defined antigen specificity: role in autoimmunity and cancer

Summary:  There is increasing evidence that agonist ligand presentation either intrathymically or extrathymically plays a crucial if not essential role in the generation of regulatory T cells (Tregs). Thus, it is possible to induce Tregs of any desired specificity in vivo. The same goal can be achieved in vitro by expanding antigen‐specific CD4+ T cells and retrovirally transducing them. In contrast, in vitro expansion of Tregs is limited to antigens that have resulted in Treg generation in vivo. Antigen‐specific Tregs can be used in cellular therapy with the goal to prevent autoimmune disease or even to interfere with established autoimmunity. The latter requires that the Tregs can suppress effector cells that have already caused harm, which is possible because of the antigen‐dependent homing properties of Tregs, i.e. these cells can accumulate in antigen‐draining lymph nodes and exit into inflamed tissue. Generally, the in vivo interference is dependent on cytokines such as transforming growth factor‐β and interleukin‐10 that were dispensable in in vivo analysis of immunosuppression. The precise mechanisms of suppression remain enigmatic, however, but may be further elucidated by the molecular analysis of suppressed versus non‐suppressed T cells.

Development of novel efficient SIN vectors with improved safety features for Wiskott-Aldrich syndrome stem cell based gene therapy.

Gene therapy is a promising therapeutic approach to treat primary immunodeficiencies. Indeed, the clinical trial for the Wiskott-Aldrich Syndrome (WAS) that is currently ongoing at the Hannover Medical School (Germany) has recently reported the correction of all affected cell lineages of the hematopoietic system in the first treated patients. However, an extensive study of the clonal inventory of those patients reveals that LMO2, CCND2 and MDS1/EVI1 were preferentially prevalent. Moreover, a first leukemia case was observed in this study, thus reinforcing the need of developing safer vectors for gene transfer into HSC in general. Here we present a novel self-inactivating (SIN) vector for the gene therapy of WAS that combines improved safety features. We used the elongation factor 1 alpha (EFS) promoter, which has been extensively evaluated in terms of safety profile, to drive a codon-optimized human WASP cDNA. To test vector performance in a more clinically relevant setting, we transduced murine HSPC as well as human CD34+ cells and also analyzed vector efficacy in their differentiated myeloid progeny. Our results show that our novel vector generates comparable WAS protein levels and is as effective as the clinically used LTR-driven vector. Therefore, the described SIN vectors appear to be good candidates for potential use in a safer new gene therapy protocol for WAS, with decreased risk of insertional mutagenesis.

Intrahepatic regulatory T cells in autoimmune hepatitis are associated with treatment response and depleted with current therapies

BACKGROUND & AIMS Autoimmune hepatitis (AIH) is a chronic autoimmune liver disease usually requiring life-long immunosuppression. The mechanisms for disease initiation and chronicity are largely unknown. A contribution of deficient regulatory T cells (Tregs) in the blood was controversially discussed recently. So far investigations in the target organ have been limited to single parameter analysis in untreated AIH. METHODS We retrospectively analysed the pattern of liver infiltrating T, B and regulatory T cells quantitatively with simultaneous multicolour immunofluorescence before (n=45) and under (n=31) therapy in adult AIH type 1 (AIH-1) patients. RESULTS Intrahepatic CD4(+) cells dominate over CD8(+) at diagnosis, but with increasing disease activity the CD4(+)/CD8(+) ratio approached one. While there is no change of Tregs in the blood, they are enriched with effector T cells (Teffs) within the liver of patients with untreated AIH-1 with a constant Treg/Teff ratio. Even more importantly, immunosuppression mostly with steroids and azathioprine caused a disproportional loss of intrahepatic Tregs. Patients reaching biochemical remission had higher intrahepatic Treg/Teff and Treg/B cell ratios compared to patients failing to reach remission. In vitro proliferation of Tregs seemed to be more suppressed by prednisolone than expansion of Teffs. Furthermore, intraportal B cells correlated with serum IgG suggesting an autochthonous intrahepatic IgG production. CONCLUSIONS Intrahepatic Tregs are rather enriched than numerically deficient in untreated AIH-1. The disproportional decrease of intrahepatic Tregs during therapy might explain high relapse rates after discontinuation of immunosuppression. Thus, future therapies increasing intrahepatic immunoregulation might be better suited for long-term control of AIH.

PD-L1 blockade effectively restores strong graft-versus-leukemia effects without graft-versus-host disease after delayed adoptive transfer of T-cell receptor gene-engineered allogeneic CD8 T cells

Adoptive transfer (AT) of T cells forced to express tumor-reactive T-cell receptor (TCR) genes is an attractive strategy to direct autologous T-cell immunity against tumor-associated antigens. However, clinical effectiveness has been hampered by limited in vivo persistence. We investigated whether the use of major histocompatibility complex-mismatched T cells would prolong the in vivo persistence of tumor-reactive TCR gene expressing T cells by continuous antigen-driven proliferation via the endogenous potentially alloreactive receptor. Donor-derived CD8(+) T cells engineered to express a TCR against a leukemia-associated antigen mediated strong graft-versus-leukemia (GVL) effects with reduced graft-versus-host disease (GVHD) severity when given early after transplantation. AT later after transplantation resulted in a complete loss of GVL. Loss of function was associated with reduced expansion of TCR-transduced T cells as assessed by CDR3 spectratyping analysis and PD-1 up-regulation on T cells in leukemia-bearing recipients. PD-L1 blockade in allogeneic transplant recipients largely restored the GVL efficacy without triggering GVHD, whereas no significant antileukemia effects of PD-L1 blockade were observed in syngeneic controls. These data suggest a clinical approach in which the AT of gene-modified allogeneic T cells early after transplantation can provide a potent GVL effect without GVHD, whereas later AT is effective only with concurrent PD-L1 blockade.

HCV-Induced Immune Responses Influence the Development of Operational Tolerance After Liver Transplantation in Humans

Persistent HCV infection does not preclude the establishment of liver allograft tolerance in humans. Turning the Tables on Tolerance When it comes to transplantation, chronic viral infection may not be so bad after all. Bohne et al. demonstrate that chronic infection with hepatitis C virus (HCV) does not prevent the development of tolerance in liver transplant patients. Animal studies have previously indicated that immune responses to infection prevent the establishment of transplantation tolerance, which has resulted in the exclusion of individuals with persistent infection from transplantation tolerance trials. This prospective trial of immunosuppression withdrawal in HCV-infected liver transplant recipients found that the HCV-induced immune response did not influence outcome. Rather, tolerance induction was associated with expression of immunoregulatory genes that were specific for HCV infection. Thus, HCV infection not only does not always prevent the development of transplantation tolerance but also may actually contribute to restraining antitransplant immune responses. Pathogen-induced immune responses prevent the establishment of transplantation tolerance in experimental animal models. Whether this occurs in humans as well remains unclear. The development of operational tolerance in liver transplant recipients with chronic hepatitis C virus (HCV) infection allows us to address this question. We conducted a clinical trial of immunosuppression withdrawal in HCV-infected adult liver recipients to elucidate (i) the mechanisms through which allograft tolerance can be established in the presence of an ongoing inflammatory response and (ii) whether anti-HCV heterologous immune responses influence this phenomenon. Of 34 enrolled liver recipients, drug withdrawal was successful in 17 patients (50%). Tolerance was associated with intrahepatic overexpression of type I interferon and immunoregulatory genes and with an expansion of exhausted PD1/CTLA4/2B4-positive HCV-specific circulating CD8+ T cells. These findings were already present before immunosuppression was discontinued and were specific for HCV infection. In contrast, the magnitude of HCV-induced proinflammatory gene expression and the breadth of anti-HCV effector T cell responses did not influence drug withdrawal outcome. Our data suggest that in humans, persistent viral infections exert immunoregulatory effects that could contribute to the restraining of alloimmune responses, and do not necessarily preclude the development of allograft tolerance.

Genetic predisposition and environmental danger signals initiate chronic autoimmune hepatitis driven by CD4+ T cells

Autoimmune hepatitis (AIH) is defined as a chronic liver disease with loss of tolerance against liver tissue eventually leading to cirrhosis if left untreated. 80%‐90% of patients can be treated with a life‐long immunosuppression. Unfortunately, there are strong drug‐related side effects and steroid‐refractory patients. Therefore, there is a need for a model system to investigate the complex immunopathogenesis of this chronic disease and subsequently to develop new therapeutic interventions. We developed a new model of experimental murine AIH (emAIH) by a self‐limited adenoviral infection with the hepatic autoantigen formiminotransferase cyclodeaminase (FTCD). After an initial transient hepatitis there was a chronic evolving AIH, finally leading to portal and lobular fibrosis. We could show that the genetic predisposition provided by the NOD background was essential for creating a fertile field for the development of liver‐specific autoimmunity. However, a strong environmental trigger was additionally necessary to initiate the disease. Besides the break of humoral tolerance, T‐cell tolerance against hepatic self‐antigens was also broken and CD4+ T cells were identified as essential drivers of the disease. As the disease was successfully treated with prednisolone and budesonide, the model will be helpful to develop and test new therapeutic interventions. Conclusion: We developed a new murine AIH model closely resembling AIH in patients that explains the mechanisms of AIH pathophysiology. In addition, emAIH provides options to test therapeutic alternatives for patients not achieving remission, with reduced side effects of chronic nonspecific immunosuppression. (Hepatology 2013;58:718–728)

The autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy or autoimmune polyglandular syndrome type 1.

Autoimmune polyglandular syndromes are rare autoimmune endocrinopathies that are associated with nonendocrine autoimmunopathies. Autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy (APECED), also named autoimmune polyglandular syndrome type 1 (APS-1), is distinguished from autoimmune polyglandular syndrome 2 (APS-2). Major disease components of APECED are adrenal insufficiency, hypoparathyroidism, and candidiasis. The diagnosis is established by the presence of two out of the three components. Minor clinical features include autoimmune hepatitis, which occurs in up to 20% of APECED patients, and ranges from a mild to a fulminant course. The disease mostly affects juvenile patients from Sardegna, Italy, Finland, and Iran (Iranian Jews), but it also occurs in other ethnic groups. The AIRE gene responsible for APECED is expressed in cells involved in induction and maintenance of immune tolerance. Genetic alterations of the single gene are associated with APECED. Because a specific therapy is not currently available, treatment consists of hormone replacement and caring for clinical symptoms.