Autosomal recessive complete interferon γ receptor 1 (IFNγR1) deficiency, known as one genetic etiology of Mendelian Susceptibility to Mycobacterial Disease (MSMD), is a life-threatening congenital disease leading to premature death in early childhood due to infections mainly with weakly virulent mycobacteria. Current therapeutic options are limited to antibiotic administration or hematopoietic stem cell transplantation. Our research group previously established a lentiviral gene therapy approach, feasible to restore antimycobacterial activity in an IFNγR1-deficient mouse model of MSMD. Here, we used a human lentiviral mediated gene therapy approach for IFNγR1-deficiency and pave the way for the first causative treatment of IFNγR1-deficiency in human MSMD patients.

To correct the cellular phenotype of IFNγR1-deficient cells, we developed third generation SIN lentiviral vectors expressing the human IFNγR1 cDNA constitutively from a viral SFFV or physiological EFS promotor. We demonstrate stable receptor reconstitution with a 10- to 15-fold increase of CD119 (IFNγR1) in an IFNγR1-KO HeLa cell model. Overexpression of IFNγR1 was associated with a restored response to IFNγ without interfering type I interferon response. Detailed evaluation of the IFNγ downstream signaling pathway revealed a 20-fold phosphorylation of STAT1 upon IFNγ-stimulation and normalized activation of the IFNγ downstream targets SOCS3, MHC-II and LPM7, which was comparable to wildtype HeLa cells. In addition, transduction of SV40-immortalized and primary fibroblasts from IFNγR1-deficient MSMD patients was able to recover IFNγR1 expression and functional type II interferon response in both cell types.

We present the first gene therapy approach to treat patients suffering from AR complete IFNγR1 deficiency.