Browsing by Subject "Immunodeficiency"

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Open Access
Characterization of inherited IRAK-4 deficiency in a patient with acute HHV-6 encephalitis
(2023-07) Demir, Zeynep Güneş Tepe
Human herpesvirus-6 (HHV-6), a ubiquitous virus among humans, typically causes acute febrile illness in children, whereas the majority remain asymptomatic. HHV-6 infection can rarely cause encephalitis, with unknown pathogenesis. We hypothesized that inborn single-gene defects may underlie susceptibility to HHV-6 encephalitis in otherwise healthy children. We performed whole-exome sequencing on genomic DNA of a male child diagnosed with acute HHV-6 encephalitis and found a novel homozygous missense variation (NM_016123.4:c.G236A:p.C79Y) in Interleukin-1 receptor-associated kinase 4 (IRAK4), which is involved in the Toll-Interleukin-1 receptor signaling pathway. Sanger sequencing confirmed that both parents and the sibling were heterozygotes. The p.C79Y that affected an evolutionary conserved residue was predicted to be damaging by in silico algorithms. We found that IRAK-4 expression was severely reduced in patient’s leukocytes. There were similar levels of wild-type (WT) and mutant IRAK-4 when transiently over-expressed in HEK293 cells, however mutant IRAK-4 expression was dramatically decreased upon cycloheximide treatment, compared to the WT. This indicated that the p.C79Y might impair IRAK-4 stability. We found that patient’s leukocytes had diminished innate immune responses to various stimuli inducing different Toll-like receptors and cytosolic nucleic acid sensors, compared to the healthy controls. We also generated IRAK4 knockout HEK293 cells by CRISPR-Cas9 genome editing. Transient expression of mutant IRAK-4 had significantly reduced NFκB-dependent luciferase activity, compared to the WT in IRAK4 knockout cells treated with IL-18. Collectively, the p.C79Y impaired both the expression and function of IRAK-4, leading to diminished immune responses against bacterial and viral stimuli in patient’s leukocytes. Overall, this was the first study demonstrating that inborn errors of immunity could underlie isolated acute HHV-6 encephalitis. Our findings also widened the known genotypic and phenotypic spectrum of inherited IRAK-4 deficiency in humans.
Open Access
Human STAT3 variants underlie autosomal dominant hyper-IgE syndrome by negative dominance
(Rockefeller University Press, 2021-06-17) Asano, T.; Khourieh, J.; Zhang, P.; Rapaport, F.; Spaan, A. N.; Li, J.; Lei, W. T.; Pelham, S. J.; Hum, D.; Chrabieh, M.; Han, J. E.; Guérin, A.; Mackie, J.; Gupta, S.; Saikia, B.; Baghdadi, J. E. I.; Fadil, I.; Bousfiha, A.; Habib, T.; Marr, N.; Ganeshanandan, L.; Peake, J.; Droney, L.; Williams, A.; Celmeli, F.; Hatipoglu, N.; Özçelik, Tayfun; Picard, C.
Most patients with autosomal dominant hyper-IgE syndrome (AD-HIES) carry rare heterozygous STAT3 variants. Only six of the 135 in-frame variants reported have been experimentally shown to be dominant negative (DN), and it has been recently suggested that eight out-of-frame variants operate by haploinsufficiency. We experimentally tested these 143 variants, 7 novel out-of-frame variants found in HIES patients, and other STAT3 variants from the general population. Strikingly, all 15 out-of-frame variants were DN via their encoded (1) truncated proteins, (2) neoproteins generated from a translation reinitiation codon, and (3) isoforms from alternative transcripts or a combination thereof. Moreover, 128 of the 135 in-frame variants (95%) were also DN. The patients carrying the seven non-DN STAT3 in-frame variants have not been studied for other genetic etiologies. Finally, none of the variants from the general population tested, including an out-of-frame variant, were DN. Overall, our findings show that heterozygous STAT3 variants, whether in or out of frame, underlie AD-HIES through negative dominance rather than haploinsufficiency.