A 3-year-old girl who presented soon after birth with recurrent urosepsis and refractory oral candidiasis despite oral fluconazole therapy. The details of the patient's clinical features were previously described, and are summarized in Table 1. She also suffered from CMV pneumonitis, mycobacterial lung disease and hepatitis of possible autoimmune etiology. A mutation was found in the DNA binding domain (DBD) of STAT1; c.1154C>T, p.T385M. The patient's T cells exhibited STAT1 hyper-phosphorylation in response to treatment with IFN-beta as compared to T cells of control subjects. Analysis of her circulating CD4+ T cells revealed increased frequencies of IFN-gamma+CD4+ (TH1 type) T cells, and decreased frequencies of IL-17+CD4+ (TH17 type) T cells, consistent with the effects of the STAT1 GOF mutation of TH cell skewing.
At age 2 years, and despite medical therapy, she continued to suffer from unrelenting lung infections, giving the impetus for HSCT. She received unmanipulated, CMV seronegative, umbilical cord HSC from genetically HLA-identical sister who had normal STAT1 gene sequencing. A reduced toxicity conditioning regimen with Treosulfan/Fludarabine/Thymoglobulin (ATG) was applied. She received valganciclovir (CMV blood PCR was negative at transplantation) and voriconazole prophylaxis in addition to the anti-bacterial (ciprofloxacin) and anti-mycobacterial therapies (ethambutol, cycloserine, levofloxacin), which was started at 9th months of age. The details of the HSCT procedure are presented in Table 2. The total infused stem cells was 3.4 x 105 CD34+cells/kg. Prophylaxis therapy was initiated, consisting of cyclosporine (CsA) and corticosteroid (CS) for GvHD and defibrotide for sinusoidal obstruction syndrome (SOS). Hematological recovery was achieved for granulocytes on day +28 and for platelets on day +41. Despite oral valganciclovir prophylaxis, she had CMV infection at day +4, which was controlled with ganciclovir therapy. Screening for other viral agents including EBV, HSV type 1 and 2, adenovirus, parvovirus and HHV-6 were negative during the follow up.
There were no signs for acute or chronic GvHD and due to mixed lymphocyte chimerism (23% donor) on day +32, CsA was stopped on day +40. At day +83, she suffered from acute toxic hepatitis that was ascribed to prolonged anti-TB prophylaxis, which resolved after drug discontinuation. Sequential chimeric analyses at days +90, +153, +190, +270 and +420 post-transplant showed 80%, 90%, 85% and 82% and 100% donor chimerism, respectively. The chimerism increased spontaneously after stopping immunosuppressive drugs without other interventions. At day +720, the whole blood and lymphocyte (including both T and B cells) chimerism levels were 100% donor cells. Lymphocyte subset analysis at that time revealed the peripheral blood CD3+ T cells at 3190/mm3 (58%), CD3+CD4+ T cells at 1815/mm3 (33%), CD3+CD8+ T cell at 1265/mm3 (23%), CD19+ B cells at 1870/mm3 (34%) and CD16+56+ NK cells at 330/mm3 (6%).
To confirm the resolution of her underlying STAT1 GOF signaling phenotype post -transplantation, we compared the induction of STAT1 phosphorylation in her CD4+ T cells obtained pre- and post-transplant in response to treatment with IFN-beta. Analysis revealed that the enhanced STAT1 phosphorylation previously noted upon treatment of her CD4+ T cells with IFN-beta significantly decreased down to normal control levels following transplantation (p<0.0001, Fig. 1A and B). Similarly, her dysregulated IFN-gamma/IL-17 CD4+/CD8+ T cells responses were also normalized (Fig. 2). She is now at 24 months after transplantation with continued 100% donor chimerism without medication.