Gain-of-function IkB-alpha mutation associated with severe recurrent mycobacterial disease without anhidrotic ectodermal dysplasia
Marcela
Moncada-Vélez1, 2*,
Alison Joanne
Lee3,
Capucine
Picard4, 5, 6, 7,
Genevieve
Llanora3,
Chiung-Hui
Huang3,
Laurent
Abel4, 5,
Bee-Wah
Lee8,
Jean-laurent
Casanova1, 4, 5, 6, 9,
Jacinta
Bustamante4, 5, 9,
Lynette Pei-Chi
Shek3, 8 and
Stéphanie
Boisson-Dupuis1, 4
-
1
The Rockefeller University, St. Giles Laboratory of Human Genetics of Infectious Diseases, United States
-
2
University of Antioquia, Group of Primary Immunodeficiencies, Sede de Investigación Universitaria-SIU, Colombia
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3
National University Children's Medical Institute (KTP-NUCMI), National University Hospital, Division of Allergy and Immunology, Department of Paediatrics, Khoo Teck Puat, Singapore
-
4
Necker Hospital for Sick Children, INSERM, France
-
5
Paris Descartes University, Imagine Institute, France
-
6
Necker Hospital for Sick Children, Pediatric Hematology-Immunology Unit, France
-
7
Necker Hospital for Sick Children, Center for the Study of Primary Immunodeficiencies, France
-
8
National University of Singapore, Department of Pediatrics, Singapore
-
9
Howard Hughes Medical Institute, United States
The NF-kB signal transduction is an inducible pathway which regulates the adaptive and innate immune response, as well as T-cell development through induction or repression of gene transcription. The NF-kB family of transcription factors comprises five related proteins that interact to form complex dimers. At rest, NF-kB dimers are bound to the inhibitory IkB family of proteins, mainly IkB-alpha in immune cells. Degradation of the inhibitory IkB protein is initiated through phosphorylation by the IkB kinase (IKK) complex, which consists of two catalytically active kinases, IKK-alpha and IKK-beta, and the regulatory subunit IKK-gamma (NF-kB essential modulator: NEMO). In the canonical pathway, TLR ligands and cytokines such as TNF or IL-1beta induce IKK-beta unit to phosphorylate the inhibtory IkB proteins, which include IkB-alpha, IkB-beta, and IkB-epsilon. This results in its degradation, releasing the bound NF-kB dimers (canonical pathway) into the nucleus, which bind to promoter sites in various genes leading to transcription activation or suppression. Mutations in the different components of this pathway have been described in humans. Hypomorphic mutations in the IKK-gamma (NEMO) gene lead to anhidrotic ectodermal dysplasia (EDA) characterized by hypohidrosis, widely spaced cone- or peg-shaped teeth, and hypotrichosis. The patients also suffer from immunodeficiency (EDA-ID), experiencing infections mainly caused by invasive pyogenic bacteria, mycobacteria and to a lesser extent parasites, viruses and fungi. Homozygous loss-of-functions mutations in IKBKB, encoding IKK-beta, have also been described. The patients display hypogammaglobulinemia, an excess of naïve T and B cells and suffer from bacterial, viral and fungal infections with or without the clinical signs of EDA. EDA-ID is also associated with hypermorphic (i.e. Gain-of-function, GOF) mutation in the NFKBIA gene, encoding IkB-alpha and resulting in a GOF of the inhibitory protein and thus inactivation of the NF-kB pathway. All the children suffered from EDA with immunodeficiency in varying degrees. We describe a 9 years old Chinese girl, presenting with immunodeficiency characterized by severe infections by Klebsiella pneumonia, Pseudomonas aeruginosa and recurrent episodes of mycobacterial infections (tuberculous and non-tuberculous), successfully treated with anti-mycobacterial therapy and recombinant IFN-gamma. Immunophenotyping showed high counts of circulating lymphocytes (B and T) and quantities of memory and naïve T and B cells were of acceptable ranges. The lymphocyte proliferation analysis showed an overall normal response of the patient’s cells, with perhaps a low response to ConA and high concentration of anti-CD3. In addition, due to the mycobacterial infection, the patient’s blood was tested for IFN-gamma and IL-12 production. The patient’s cells showed diminished production of both IFN-gamma and IL-12 after BCG+IL-12 and BCG+ IFN-gamma, respectively as compared to the travel control. Whole exome-sequencing was performed on gDNA from the patient and we found a heterozygous mutation in NFKBIA affecting the serine at position 36 (S36Y). Immune cells as well as dermal fibroblasts from the patient carry the heterozygous missense mutation, apparently at the same level. Familial segregation analysis showed that both parents are wild-type for the substitution; the mutation thus appeared de novo in the patient, underlying an autosomal dominant (AD) condition. Heterozygous mutations in NFKBIA have been previously associated with AD-EDA-ID. In particular, this mutation was reported in a patient with mild AD-EDA-ID and non-infectious systemic inflammation. At the molecular level, mutations in NFKBIA have previously been shown to be GOF, preventing the correct phosphorylation of IkB-alpha on Serine 32 and 36, thereby impairing the degradation of this inhibitory protein, and in turn sequestering NF-kB in the cytoplasm. We then analyzed the IkB-alpha phosphorylation and subsequent degradation in primary fibroblasts from the patient, a healthy control and a NEMO-deficient cell line after TNF-alpha and IL-1-beta stimulation. We found that IkB-alpha was phosphorylated on Serine 32 after TNF-alpha stimulation in control and in patient’s cells, as compared with a NEMO-deficient patient. However, we observe an impaired, but not abolished IkB-alpha degradation in the patient’s cells compared to the healthy control (positive control) and the NEMO-deficient cells (negative control). The same results were obtained after stimulation with IL-1beta. Altogether, IkB-alpha mutations should be suspected in children with bacterial and mycobacterial infections even without EDA clinical presentation. In addition, a treatment with rIFN-gamma injection may be proposed to cure all infections.
Acknowledgements
We would like to thank all the member of the Laboratory of Human Genetics of Infectious Diseases from both Paris and New York. A special thank you is extended to Tatiana Kochetkov for the cell culture help and to Yelena Nemirovskaya for the outstanding administrative support.
Keywords:
mycobacterial infections,
NFKBIA,
IkBalpha,
anhidrotic ectodermal dysplasia with immunodeficiency (EDA-ID),
Gain-of-function mutation
Conference:
IMMUNOCOLOMBIA2015 - 11th Congress of the Latin American Association of Immunology - 10o. Congreso de la Asociación Colombiana de Alergia, Asma e Inmunología, Medellin, Colombia, 13 Oct - 16 Oct, 2015.
Presentation Type:
Oral Presentation
Topic:
Immunodeficiencies
Citation:
Moncada-Vélez
M,
Lee
A,
Picard
C,
Llanora
G,
Huang
C,
Abel
L,
Lee
B,
Casanova
J,
Bustamante
J,
Shek
L and
Boisson-Dupuis
S
(2015). Gain-of-function IkB-alpha mutation associated with severe recurrent mycobacterial disease without anhidrotic ectodermal dysplasia.
Front. Immunol.
Conference Abstract:
IMMUNOCOLOMBIA2015 - 11th Congress of the Latin American Association of Immunology - 10o. Congreso de la Asociación Colombiana de Alergia, Asma e Inmunología.
doi: 10.3389/conf.fimmu.2015.05.00354
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Received:
28 May 2015;
Published Online:
15 Sep 2015.
*
Correspondence:
PhD. Marcela Moncada-Vélez, The Rockefeller University, St. Giles Laboratory of Human Genetics of Infectious Diseases, New York, New York, 10065, United States, mmoncad1@jhu.edu