Amarilla B Mandola1, Nigel Sharfe2, Zahra Nagdi2, Harjit Dadi2, Linda Vong3, Daniele Merico4, Bo Ngan5, Brenda Reid6, Chaim M Roifman7. 1. Canadian Centre for Primary Immunodeficiency and the Jeffrey Modell Research Laboratory for the Diagnosis of Primary Immunodeficiency, Toronto, Ontario, Canada; Division of Immunology and Allergy, Department of Paediatrics, Hospital for Sick Children, Toronto, Ontario, Canada; Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada; Department of Immunology, University of Toronto, Toronto, Ontario, Canada. 2. Canadian Centre for Primary Immunodeficiency and the Jeffrey Modell Research Laboratory for the Diagnosis of Primary Immunodeficiency, Toronto, Ontario, Canada; Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada; Division of Immunology and Allergy, Department of Paediatrics, Hospital for Sick Children, Toronto, Ontario, Canada. 3. Canadian Centre for Primary Immunodeficiency and the Jeffrey Modell Research Laboratory for the Diagnosis of Primary Immunodeficiency, Toronto, Ontario, Canada; Division of Immunology and Allergy, Department of Paediatrics, Hospital for Sick Children, Toronto, Ontario, Canada; Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada. 4. The Centre for Applied Genomics, Hospital for Sick Children, Toronto, Ontario, Canada; Deep Genomics Inc, Toronto, Ontario, Canada. 5. Department of Laboratory Medicine and Pathobiology, Hospital for Sick Children, Toronto, Ontario, Canada. 6. Canadian Centre for Primary Immunodeficiency and the Jeffrey Modell Research Laboratory for the Diagnosis of Primary Immunodeficiency, Toronto, Ontario, Canada; Division of Immunology and Allergy, Department of Paediatrics, Hospital for Sick Children, Toronto, Ontario, Canada. 7. Canadian Centre for Primary Immunodeficiency and the Jeffrey Modell Research Laboratory for the Diagnosis of Primary Immunodeficiency, Toronto, Ontario, Canada; Division of Immunology and Allergy, Department of Paediatrics, Hospital for Sick Children, Toronto, Ontario, Canada; Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada; Department of Immunology, University of Toronto, Toronto, Ontario, Canada. Electronic address: chaim.roifman@sickkids.ca.
Abstract
BACKGROUND: Genetic faults in several components of the nuclear factor-κB pathway cause immunodeficiency. Most defects lead to combined immunodeficiency with a range of severity. Heterozygous mutations in NFKB1 were associated with common variable immunodeficiency, however, homozygous mutations have not been described. OBJECTIVE: We studied the molecular basis of combined immunodeficiency in a patient who presented with failure to thrive, persistent EBV viremia and hepatitis, pneumocystis jirovecii pneumonitis, and generalized lymphadenopathy. METHODS: Whole genome and exome sequencing followed by Sanger confirmation were performed to identify the genetic defect. Molecular and cellular techniques were used to assess the variant impact on the nuclear factor-κB pathway and lymphocyte function. RESULTS: Genetic analysis revealed a novel homozygous mutation in NFKB1, c.2878G>A, p.Gly960Arg (G960R). This affected p105 phosphorylation and p50 formation on antigen and cytokine stimulation, as well as attenuating nuclear signal transmission. As a result, both T- and B-cell maturation and function were perturbed. The number of memory CD4+ T cells were reduced, while CD8+ T cells consisted predominately of expanded differentiated populations. The function of T cells were diminished as shown by reduced responses to mitogens as well as diminished cytokine secretion. B-cell maturation was also affected, with decreased IgD+CD27+ memory B cells while transitional B cells were increased, likely contributing to the reduced ability to produce specific antibodies. CONCLUSION: Homozygous G960R mutation in NFKB1 leads to a severe clinical presentation of combined immunodeficiency. This was associated with blockade of nuclear factor-κB pathway signaling, resulting in aberrations in T- and B-cell maturation and function.
BACKGROUND: Genetic faults in several components of the nuclear factor-κB pathway cause immunodeficiency. Most defects lead to combined immunodeficiency with a range of severity. Heterozygous mutations in NFKB1 were associated with common variable immunodeficiency, however, homozygous mutations have not been described. OBJECTIVE: We studied the molecular basis of combined immunodeficiency in a patient who presented with failure to thrive, persistent EBV viremia and hepatitis, pneumocystis jirovecii pneumonitis, and generalized lymphadenopathy. METHODS: Whole genome and exome sequencing followed by Sanger confirmation were performed to identify the genetic defect. Molecular and cellular techniques were used to assess the variant impact on the nuclear factor-κB pathway and lymphocyte function. RESULTS: Genetic analysis revealed a novel homozygous mutation in NFKB1, c.2878G>A, p.Gly960Arg (G960R). This affected p105 phosphorylation and p50 formation on antigen and cytokine stimulation, as well as attenuating nuclear signal transmission. As a result, both T- and B-cell maturation and function were perturbed. The number of memory CD4+ T cells were reduced, while CD8+ T cells consisted predominately of expanded differentiated populations. The function of T cells were diminished as shown by reduced responses to mitogens as well as diminished cytokine secretion. B-cell maturation was also affected, with decreased IgD+CD27+ memory B cells while transitional B cells were increased, likely contributing to the reduced ability to produce specific antibodies. CONCLUSION: Homozygous G960R mutation in NFKB1 leads to a severe clinical presentation of combined immunodeficiency. This was associated with blockade of nuclear factor-κB pathway signaling, resulting in aberrations in T- and B-cell maturation and function.