Evaluation of patients with ALPS-like syndromes

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Abstract

This project has continued to generate newly defined syndromes characterized by chronic lymphadenopathy, splenomegaly and autoimmune phenomena. Initially this involved ALPS-like patietns with gain-of-function mutations involving the genes that encode NRAS and KRAS. These resulted in the hyperactivation of the RAS-RAF-ERK pathway and suppression of the pro-apoptotic protein BIM. This in turn resulted in defective T cell apoptosis after IL-2 withdrawal, but normal T cell and B cell apoptosis in response to staurosporine, etoposide, cisplatin and radiation as well as a normal Fas pathway induction of apoptosis. The low levels of BIM also affected the apoptosis induced by T-cell reactivation. These intial observations have lead to identifying 12 patients with somatic gain of function NRAS or KRAS mutations with many presenting early in childhood with a phenotype that shares features of acute myelomonocytic leukemia (AMML) but it is not an aggressive or malignant disorder unlike AMML. This disroder is now named RAS Associated Leukoproliferative Disorder (RALD). We are workng on potential markers that better define how to distinguish this somatic NRAS mutation disorder from the same mutatons that result in JMML. Most recently we have characterized two additional genetic disorders that share certain features with ALPS and the patients evaluated came from the cohort of patients refered to the NIH to rule out ALPS. Included among these new syndromes is a child with a homozygous loss of function defect in protein kinase C delta that causes lymphadenopathy, B cell hyperproliferation, expansion of CD5+/CD20+ B cells, increased immunoglobulins, autoantibody production and defective B cell apoptosis as well as chronic EBV viremia associated with a defect in NK cell function. The ex vivo findings of B cell hyperproliferrration could be recapitulated in normal mononuclear cells by PKC delta knock down and the patient EBV transsformed B cells could be partially rescued from the ex vivo PMA induced apoptotic defect by insertion of wild-type PKC delta. This patient defines a new entity in monogenic apoptotic defects that primarily affects B cells and also interferes with normal NK cell cytotoxicity (the latter for at present an unknown mechanism) that appears to increase the susceptibility to chronic EBV viremia. Importantly this patient responded dramatically to rapamycin therapy with marked decrease in the massive splenomegaly and dimiinished B cell activation. Most recently, we have characterized a group of patients with heterozygous mutations in PI3 kinase p110 that result in a gain of function of this protein associated with incresaed risk for sinopulmonary infections, lymphoaccumulation and autoimmunity. The clinical phenotype of these patients has expanded to include a hyper IgM syndrome like presenation and in addition these patients have an increased risk for lymphoid malignancy. We are currently working with Novartis on the initiation of a clinical trial used a specific inhibitor of PI3 kinase p110 that the company developed and has completed phase 1 trials demonstrating its lack of toxicity in humans. The FDA has already provided preliminary review of this proposed cooperative trial and it is anticipated that this will start in early 2015. The Immunology Service will provide specific flow cytometric and intracellular functional testing as part of the monitoring program for this clinical trial. Finally, additional patient samples within the referral cohort to rule out ALPS, in whom ALPS and RALD have been ruled out, are being evaluated for either new immunologic defects at the genomic DNA level or for the defects noted above.