Antisense oligonucleotides (AONs) are versatile molecules that can be used to modulate gene expression by binding to RNA. The therapeutic potential of AONs appears particularly high in the central nervous system, due to excellent distribution and uptake in brain cells, as well as good tolerability in clinical trials thus far. Nonetheless, immune stimulation in response to AON treatment in the brain remains a concern. For this reason we performed RNA sequencing analysis of brain tissue from mice treated intracerebroventricularly with phosphorothioate, 2′-O-methyl modified AONs. A significant upregulation of immune system associated genes was observed in brains of AON treated mice, with the striatum showing largest transcriptional changes. Strongest upregulation was seen for the antiviral enzyme 2′-5′-oligoadenylate synthase-like protein 2 (Oasl2) and Bone marrow stromal antigen 2 (Bst2). Histological analysis confirmed activation of microglia and astrocytes in striatum. The upregulation of immune system associated genes was detectable for at least 2 months after the last AON administration, consistent with a continuous immune response to the AON.

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Objectives Amniotic fluid is essential for proper fetal development. In the case of severe polyhydramnios associated with low fetal growth, a number of different underlying disorders must be considered. One such condition is congenital central hypoventilation syndrome (CCHS) or Ondine’s curse, a rare genetic disease caused by mutation of the PHOX2B gene. The incidence of CCHS is estimated to be 1 case in 200,000 live births. No publications have been made to date on the intrauterine period findings. This precludes an early intrauterine diagnosis and impedes ethically responsible therapeutic options. Case presentation A 37-year-old patient presented in her second pregnancy with a small for gestation fetus and severe polyhydramnios evidenced in the third trimester ultrasound (US) study. There were no previous signs of maternal diabetes or fetal abnormalities at US. During the immediate postpartum period, the newborn presented repeated apneas with cyanosis and hypo-responsiveness. Neonatal arterial blood gas testing revealed severe respiratory acidosis requiring orotracheal intubation and admission to the Neonatal Intensive Care Unit. Over the following days, all imaging and functional test findings were within normal ranges. A de novo pathogenic PHOX2B variant was identified. Conclusions Despite a high mortality rate, no neurological sequelae or other systemic diseases were recorded, thanks to multidisciplinary and coordinated follow-up.