Activated phosphoinositide 3-kinase δ syndrome (APDS) is a recently described autosomal dominant primary immunodeficiency (PID), caused by the mutations in PIK3CD gene. The manifestations of APDS mainly include recurrent respiratory tract infections, persistent Epstein-Barr virus (EBV)/ cytomegalovirus (CMV)infections, lymphadenopathy, splenomegaly, CD4+T cells lymphopenia, and hyper-IgM syndrome. PIK3CD encodes p110δ, the catalytic subunit of phosphatidylinositol 3-kinase (PI3K) which mainly expresses in leukocytes, being critical for their proliferation, activation and survival. Gain-of-function (GOF) PIK3CD mutations lead to PI3Kδ hyperactivity, with the downstream mediators Akt and mammilian target of rapamycin (mTOR) hyperphosphorylated. Patient-derived lymphocytes had increased levels of phosphatidylinositol 3,4,5-trisphosphate and phosphorylated AKT protein. Hyperactivation of mTOR increases phosphorylation of kinases and increased glycolysis that results in enhanced proliferation and senescence of terminally differentiated CD8+ Tcell populations.~The optimal treatment for these APDS patients is not yet determined; however, there are many kinds of therapeutic approaches (anti-infection prophylaxis, immunoglobulin replacement, conventional immunosuppressants, PI3K/mTOR inhibitors and hematopoietic stem cell transplantation). The APDS patients frequently receive treatment with immunoglobulin replacement and antibiotics. Hematopoietic stem cell transplantation (HSCT) has been currently curative in APDS patients; however, longer-term follow-up to determine the degree of donor chimerism and efficacy is required. There are several subjects without a prompt suitable matched donor or for whom the critical disease conditions force to postpone HSCT.The mammalian/mechanistic target of inhibitor rapamycin was reported to improve circulating T-cell profiles. Individual patients in previous studies experienced a decrease in nonneoplastic lymphoproliferation while taking rapamycin.~The investigators in this study hope to evaluate the efficacy and safety of rapamycin in the treatment for carefully selected patients with APDS.
The purpose of this proposed research is to evaluate the efficacy and safety of the rapamycin therapy in patients with activated phosphoinositide 3-kinase δ syndrome (APDS).