RESUMO
Viruses that are typically benign sometimes invade the brainstem in otherwise healthy children. We report bi-allelic DBR1 mutations in unrelated patients from different ethnicities, each of whom had brainstem infection due to herpes simplex virus 1 (HSV1), influenza virus, or norovirus. DBR1 encodes the only known RNA lariat debranching enzyme. We show that DBR1 expression is ubiquitous, but strongest in the spinal cord and brainstem. We also show that all DBR1 mutant alleles are severely hypomorphic, in terms of expression and function. The fibroblasts of DBR1-mutated patients contain higher RNA lariat levels than control cells, this difference becoming even more marked during HSV1 infection. Finally, we show that the patients' fibroblasts are highly susceptible to HSV1. RNA lariat accumulation and viral susceptibility are rescued by wild-type DBR1. Autosomal recessive, partial DBR1 deficiency underlies viral infection of the brainstem in humans through the disruption of tissue-specific and cell-intrinsic immunity to viruses.
Assuntos
Encefalopatias Metabólicas Congênitas/genética , Tronco Encefálico/metabolismo , Tronco Encefálico/virologia , RNA/química , RNA/metabolismo , Alelos , Sequência de Aminoácidos , Animais , Encefalopatias Metabólicas Congênitas/patologia , Tronco Encefálico/patologia , Encefalite Viral/genética , Escherichia coli/metabolismo , Feminino , Fibroblastos/metabolismo , Fibroblastos/patologia , Fibroblastos/virologia , Herpesvirus Humano 1 , Humanos , Interferons/metabolismo , Íntrons/genética , Masculino , Camundongos , Proteínas Mutantes/metabolismo , Mutação/genética , Fases de Leitura Aberta/genética , Linhagem , RNA Nucleotidiltransferases/química , RNA Nucleotidiltransferases/deficiência , RNA Nucleotidiltransferases/genética , Receptor 3 Toll-Like/metabolismo , Replicação ViralRESUMO
Antibody deficiencies can be caused by a variety of defects that interfere with B-cell development, maturation, and/or function. Using whole-exome sequencing we found a PIK3R1 mutation in a patient with hypogammaglobulinemia and a narrow clinical phenotype of respiratory infections. Early diagnosis is crucial; careful analysis of B and T-cells followed by genetic analyses may help to distinguish activated PI3K-delta syndrome (APDS) from other, less severe, predominantly antibody deficiencies.
Assuntos
Agamaglobulinemia/genética , Fosfatidilinositol 3-Quinases/genética , Infecções Respiratórias/genética , Agamaglobulinemia/imunologia , Linfócitos B/imunologia , Criança , Classe Ia de Fosfatidilinositol 3-Quinase , Feminino , Humanos , Mutação , Fenótipo , Infecções Respiratórias/imunologia , Linfócitos T/imunologiaRESUMO
Inborn errors of TLR3-dependent type I IFN immunity in cortical neurons underlie forebrain herpes simplex virus-1 (HSV-1) encephalitis (HSE) due to uncontrolled viral growth and subsequent cell death. We report an otherwise healthy patient with HSE who was compound heterozygous for nonsense (R422*) and frameshift (P493fs9*) RIPK3 variants. Receptor-interacting protein kinase 3 (RIPK3) is a ubiquitous cytoplasmic kinase regulating cell death outcomes, including apoptosis and necroptosis. In vitro, the R422* and P493fs9* RIPK3 proteins impaired cellular apoptosis and necroptosis upon TLR3, TLR4, or TNFR1 stimulation and ZBP1/DAI-mediated necroptotic cell death after HSV-1 infection. The patient's fibroblasts displayed no detectable RIPK3 expression. After TNFR1 or TLR3 stimulation, the patient's cells did not undergo apoptosis or necroptosis. After HSV-1 infection, the cells supported excessive viral growth despite normal induction of antiviral IFN-ß and IFN-stimulated genes (ISGs). This phenotype was, nevertheless, rescued by application of exogenous type I IFN. The patient's human pluripotent stem cell (hPSC)-derived cortical neurons displayed impaired cell death and enhanced viral growth after HSV-1 infection, as did isogenic RIPK3-knockout hPSC-derived cortical neurons. Inherited RIPK3 deficiency therefore confers a predisposition to HSE by impairing the cell death-dependent control of HSV-1 in cortical neurons but not their production of or response to type I IFNs.