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CD55 Deficiency, Early-Onset Protein-Losing Enteropathy, and Thrombosis
Ahmet Ozen1, William A Comrie1, Rico C Ardy1
1From the Section of Molecular Development of the Immune System, Laboratory of Immunology (A.O., W.A.C., A.R.M., H.F.M., M.J.L.), the Clinical Genomics Program (A.O., W.A.C., A.R.M., Y.Z., H.F.M., H.C.S., M.J.L.), and the Human Immunological Diseases Section, Laboratory of Host Defenses (Y.Z., H.C.S.), National Institute of Allergy and Infectious Diseases, the Laboratory of Pathology, National Cancer Institute (S.P.), and Radiology and Imaging Sciences, Clinical Center (L.R.F.), National Institutes of Health, Bethesda, MD; the Department of Pediatrics, Division of Allergy and Immunology (A.O., E.K.-A., S.B., A. Kiykim, I.O.), and the Department of Pediatrics, Division of Pediatric Gastroenterology, Hepatology, and Nutrition (E.T., D.E.), Marmara University, Jeffrey Modell Diagnostic Center for Primary Immunodeficiency Diseases (A.O., E.K.-A., S.B., A. Kiykim, I.O.), and the Department of Pediatrics, Division of Pediatric Gastroenterology, Hepatology, and Nutrition, İstanbul University Cerrahpaşa Faculty of Medicine (Ö.F.B., T.E.), Istanbul, and the Department of Pediatrics, Division of Pediatric Gastroenterology, Hepatology, and Nutrition, Gazi University (B.D., S.S.), the Department of Pediatric Gastroenterology, Hepatology, and Nutrition, Faculty of Medicine, Başkent University (F.O., Z.B., M.G.), and the Pediatric Gastroenterology Clinic, Dr. Sami Ulus Children's Hospital (A.U.A.), Ankara - all in Turkey; Ludwig Boltzmann Institute for Rare and Undiagnosed Diseases and the CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences (R.C.A., C.D.C., N.K.S., A. Krolo, K.B.), Clinical Institute of Pathology (R.K.), the Department of Pediatrics and Adolescent Medicine (K.B.), and St. Anna Kinderspital and Children's Cancer Research Institute, Department of Pediatrics (K.B.), Medical University of Vienna, Vienna; Merck Research Laboratories (J.J.M.), and the Division of Gastroenterology, Hepatology, and Nutrition, Boston Children's Hospital, Harvard Medical School (S.B.S.), Boston; and the Department of Pediatric Gastroenterology, University Medical Center-Wilhelmina Children's Hospital (R.H.J.H.), and the Department of Rheumatology and Clinical Immunology, University Medical Center (H.L.L.), Utrecht, the Netherlands.
Background:
Studies of monogenic gastrointestinal diseases have revealed molecular pathways critical to gut homeostasis and enabled the development of targeted therapies.
Methods:
We studied 11 patients with abdominal pain and diarrhea caused by early-onset protein-losing enteropathy with primary intestinal lymphangiectasia, edema due to hypoproteinemia, malabsorption, and less frequently, bowel inflammation, recurrent infections, and angiopathic thromboembolic disease; the disorder followed an autosomal recessive pattern of inheritance. Whole-exome sequencing was performed to identify gene variants. We evaluated the function of CD55 in patients' cells, which we confirmed by means of exogenous induction of expression of CD55.
Results:
We identified homozygous loss-of-function mutations in the gene encoding CD55 (decay-accelerating factor), which lead to loss of protein expression. Patients' T lymphocytes showed increased complement activation causing surface deposition of complement and the generation of soluble C5a. Costimulatory function and cytokine modulation by CD55 were defective. Genetic reconstitution of CD55 or treatment with a complement-inhibitory therapeutic antibody reversed abnormal complement activation.
Conclusions:
CD55 deficiency with hyperactivation of complement, angiopathic thrombosis, and protein-losing enteropathy (the CHAPLE syndrome) is caused by abnormal complement activation due to biallelic loss-of-function mutations in CD55. (Funded by the National Institute of Allergy and Infectious Diseases and others.).
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