Development of a lentiviral gene therapy vector to modify effector T and NK cells to control disease activity in perforin deficient hemophagocytic lymphohistiocytosis (HLH) patients

• Applicant: Dr. Sujal Ghosh
• Subject Area: Rheumatology ; Immunology ; Pediatric and Adolescent Medicine
• Term: from 2013 to 2015
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 251204879

Hemophagocytic lymphohistiocytosis (HLH) is an immune dysregulatory disorder, which is defined by symptoms of extreme inflammation leading to fatal damage in various organs including bone marrow, liver and central nervous system. Key features are fever, splenomegaly, bleedings, dyspnea and infections due to cytopenia, hypertriglyceridemia, hypofibrinogenemia, hemophagocytosis, decreased NK cell activity, elevated ferritin and sCD25. Several primary immunodeficiencies are prone to HLH, terming these diseases hemophagocytic syndromes. In most of these disorders, genes are affected, which are part of the cytolytic secretory pathway that cause perforin and granzymes to induce apoptosis in target cells. Before the implementation of a structured protocol the 1-year survival had been very low. Nowadays with the introduction of hematopoetic stem cell transplantation (HSCT) the survival reaches > 90% in an optimal setting, though patients receiving HSCT stay at risk of developing any of the usual complications of HSCT. In patients, who lack of a well-matched donor, other curative options are warranted. In few non-malignant genetic disorders ex-vivo correction of autologous stem cells seems to be an attractive option. In the past two decades techniques for manipulations of autologous stem cells by viral transduction has enabled gene therapy protocols in a limited number of candidate diseases.In familial HLH (FHL) type II - which is supposed to constitute the largest group among patients with FHL - mutations in the PRF1 gene (coding perforin) lead to elevated antigen presentation by dendritic cells with consecutive T cell hyperactivation. The Molecular Immunology Unit at the UCL Institute of Child Health currently develops a safe and effective lentiviral gene therapy vector encoding the perforin gene, that can be used to modify autologous hematopoietic stem cells for treatment of perforin deficient HLH. Initial experiments have shown that introduction of the correct copy of the perforin gene into hematopoietic stem cells can restore the T and NK cell defects seen in the perforin deficient mice. These reconstituted mice are protected against development of HLH after viral challenge. Similarly, gene transfer into autologous peripheral T or NK cells might control disease activity in patients suffering from HLH. This task, which constitutes the project of the research fellow, will be achieved by the development of the best viral vector to promote perforin expression in T and NK cells in mouse cells. After selection of the best effector cell population, which provides correction of cytotoxic defects in the mouse model of HLH, we will assess the ability of perforin reconstituted effector cells in controlling virus induced disease in the murine model. In case of a successful gene transfer further clinical trials are supposed to be a main goal of these pre-clinical studies.

• DFG Programme: Research Fellowships
• International Connection: United Kingdom
• Host: Professor Bobby Gaspar