Topal, Yusuf; (2018) Correction of innate immune responses in XIAP deficiency using haematopoietic cell gene therapy. Doctoral thesis (Ph.D), UCL (University College London).

Abstract

X-linked inhibitor of apoptosis protein (XIAP) deficiency, caused by mutations in BIRC4, is a severe immunodeficiency with clinical features including haemophagocytic lymphohistiocytosis (HLH) and inflammatory bowel disease (IBD). Current management includes HLH treatment protocols and haematopoietic stem cell transplant (HSCT). However, survival post-HSCT for XIAP-deficient patients is significantly lower compared to patients receiving HSCT for other forms of HLH with graft versus host disease and disease relapse-associated problems. Autologous HSC gene therapy could offer an alternative treatment option and may abrogate the risk of alloreactivity. Using a XIAP-knockdown THP-1 monocyte cell line we restored NOD2-dependent TNF-α secretion following XIAP/BIRC4 gene transfer using a lentiviral vector containing codon optimised XIAP cDNA driven by the spleen focus-forming virus (SFFV) promoter (SFFV-XIAP.eGFP). Moreover, in patient cells we demonstrated restoration of TNF-α secretion in response to L18-MDP following gene correction. In a XIAP-/- mouse model, the lack of XIAP leads to impaired innate immune responses following immunization with the dectin-1 ligand curdlan. At early time points (2 hours post-curdlan administration) serum levels of IL-6, IL-10, MCP-1 and TNF-α and are significantly reduced in XIAP-/- mice compared to wild-type animals, whilst after 9 days, this profile is reversed with XIAP-/- mice secreting higher levels of pro-inflammatory cytokines together with splenomegaly due to excessive neutrophil and macrophage infiltration. To study whether gene therapy strategies could correct these defects, haematopoietic progenitors from XIAP-/- donor animals were transduced with the SFFV-XIAP.eGFP construct and injected into lethally irradiated XIAP-/- recipients. After 12 weeks reconstituted animals were challenged with curdlan and serum cytokines measured. HSC Gene therapy was able to restore immune function in XIAP-/- mice since gene-corrected animals demonstrated weight loss, spleen size and histology and cytokine profile comparable to wild-type mice. Taken together, the data presented here provides proof-of-concept for gene therapy for the treatment of XIAP deficiency.

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