RESUMO
UNLABELLED: Among patients newly infected with hepatitis C virus (HCV), only 20-30% clear the infection spontaneously. In the remaining 70% the infection persists, causing chronic liver inflammation and disease. It is well established that polymorphisms in host genes, especially in components of the innate immune response, contribute to the phenomenon of spontaneous HCV clearance. Retinoic acid inducible gene-I (RIG-I)-like helicases such as melanoma differentiation-associated gene 5 (MDA-5) are cytoplasmic sensors of viral RNA that are critical for triggering innate immune responses after infection with RNA viruses. We analyzed 14 nonsynonymous single-nucleotide polymorphisms in RIG-I-like helicase-pathway-genes comparing European patients who spontaneously cleared HCV (n = 285) or had persistent infection (n = 509). We found that polymorphic haplotypes in the MDA-5 gene IFIH1 encoding histidine at position 843 and threonine at position 946 strongly correlate with the resolution of HCV infection (odds ratio [OR]: 16.23; 95% confidence interval [CI]: 3.67-71.87; P = 1.1 × 10(-6) ). Overexpression of MDA-5 genetic variants in HEK 293 cells and in a tissue culture model of HCV infection revealed that the histidine 843/threonine 946 variant leads to increased baseline and ligand-induced expression of interferon-induced genes and confers an increased ability to suppress HCV replication. CONCLUSION: These data suggest that MDA-5 plays a significant role in the defense against HCV and that polymorphisms in MDA-5 can influence the outcome of HCV infection.
Assuntos
RNA Helicases DEAD-box/genética , Hepatite C Crônica/genética , Interações Hospedeiro-Patógeno/genética , Estudos de Casos e Controles , Feminino , Células HEK293 , Hepacivirus/fisiologia , Hepatite C Crônica/virologia , Humanos , Helicase IFIH1 Induzida por Interferon , Masculino , Polimorfismo Genético , Remissão EspontâneaRESUMO
A key host response to limit microbial spread is the induction of cell death when foreign nucleic acids are sensed within infected cells. In mouse macrophages, transfected DNA or infection with modified vaccinia virus Ankara (MVA) can trigger cell death via the absent in melanoma 2 (AIM2) inflammasome. In this article, we show that nonmyeloid human cell types lacking a functional AIM2 inflammasome still die in response to cytosolic delivery of different DNAs or infection with MVA. This cell death induced by foreign DNA is independent of caspase-8 and carries features of mitochondrial apoptosis: dependence on BAX, APAF-1, and caspase-9. Although it does not require the IFN pathway known to be triggered by infection with MVA or transfected DNA via polymerase III and retinoid acid-induced gene I-like helicases, it shows a strong dependence on components of the DNA damage signaling pathway: cytosolic delivery of DNA or infection with MVA leads to phosphorylation of p53 (serines 15 and 46) and autophosphorylation of ataxia telangiectasia mutated (ATM); depleting p53 or ATM with small interfering RNA or inhibiting the ATM/ATM-related kinase family by caffeine strongly reduces apoptosis. Taken together, our findings suggest that a pathway activating DNA damage signaling plays an important independent role in detecting intracellular foreign DNA, thereby complementing the induction of IFN and activation of the AIM2 inflammasome.
Assuntos
Apoptose/imunologia , Dano ao DNA/imunologia , DNA Viral/imunologia , Macrófagos/imunologia , Proteínas Nucleares/imunologia , RNA Polimerase III/imunologia , Transdução de Sinais/imunologia , Vaccinia virus/imunologia , Vacínia/imunologia , Animais , Apoptose/genética , Fator Apoptótico 1 Ativador de Proteases/genética , Fator Apoptótico 1 Ativador de Proteases/imunologia , Fator Apoptótico 1 Ativador de Proteases/metabolismo , Proteínas Mutadas de Ataxia Telangiectasia , Caspase 8/genética , Caspase 8/imunologia , Caspase 8/metabolismo , Proteínas de Ciclo Celular/genética , Proteínas de Ciclo Celular/imunologia , Proteínas de Ciclo Celular/metabolismo , Citosol , DNA Viral/genética , DNA Viral/metabolismo , Proteínas de Ligação a DNA/genética , Proteínas de Ligação a DNA/imunologia , Proteínas de Ligação a DNA/metabolismo , Células HEK293 , Humanos , Inflamassomos/genética , Inflamassomos/imunologia , Inflamassomos/metabolismo , Interferons/genética , Interferons/imunologia , Interferons/metabolismo , Macrófagos/metabolismo , Macrófagos/virologia , Camundongos , Proteínas Nucleares/genética , Proteínas Nucleares/metabolismo , Fosforilação/genética , Fosforilação/imunologia , Proteínas Serina-Treonina Quinases/genética , Proteínas Serina-Treonina Quinases/imunologia , Proteínas Serina-Treonina Quinases/metabolismo , RNA Polimerase III/genética , RNA Polimerase III/metabolismo , Transdução de Sinais/genética , Proteína Supressora de Tumor p53/genética , Proteína Supressora de Tumor p53/imunologia , Proteína Supressora de Tumor p53/metabolismo , Proteínas Supressoras de Tumor/genética , Proteínas Supressoras de Tumor/imunologia , Proteínas Supressoras de Tumor/metabolismo , Vacínia/genética , Vacínia/metabolismo , Vaccinia virus/genética , Vaccinia virus/metabolismo , Proteína X Associada a bcl-2/genéticaRESUMO
T-cell recognition of peptide/MHC complexes is flexible and can lead to differential activation, but how interactions with agonist (full activation) or partial agonist (suboptimal activation) peptides can shape immune responses in vivo is not well characterized. We investigated the effect of stimulation by agonist or partial agonist ligands during initial CD4(+) T-cell priming, and subsequent T-B-cell cognate interactions, on antibody production by anti-chromatin B cells. We found that autoantibody production required TCR recognition of an agonist peptide at the effector stage of B-cell activation. However, interaction with a weak agonist ligand at this effector stage failed to promote efficient autoantibody production, even if the CD4(+) T cells were fully primed by an agonist peptide. These studies suggest that the reactivity of the TCR for a target self-peptide during CD4(+) T-B-cell interaction can be a critical determinant in restraining anti-chromatin autoantibody production.
