Neonatal detection of Aicardi Goutières Syndrome by increased C26:0 lysophosphatidylcholine and interferon signature on newborn screening blood spots

Abstract

Background: Aicardi Goutières Syndrome (AGS) is a heritable interferonopathy associated with systemic autoinflammation causing interferon (IFN) elevation, central nervous system calcifications, leukodystrophy and severe neurologic sequelae. An infant with TREX1 mutations was recently found to have abnormal C26:0 lysophosphatidylcholine (C26:0 Lyso-PC) in a newborn screening platform for X-linked adrenoleukodystrophy, prompting analysis of this analyte in retrospectively collected samples from individuals affected by AGS.

Methods: In this study, we explored C26:0 Lyso-PC levels and IFN signatures in newborn blood spots and post-natal blood samples in 19 children with a molecular and clinical diagnosis of AGS and in the blood spots of 22 healthy newborns. We used Nanostring nCounter™ for IFN-induced gene analysis and a high-performance liquid chromatography with tandem mass spectrometry (HPLC MS/MS) newborn screening platform for C26:0 Lyso-PC analysis.

Results: Newborn screening cards from patients across six AGS associated genes were collected, with a median disease presentation of 2months. Thirteen out of 19 (68%) children with AGS had elevations of first tier C26:0 Lyso-PC (>0.4μM), that would have resulted in a second screen being performed in a two tier screening system for X-linked adrenoleukodystrophy (X-ALD). The median (95%CI) of first tier C26:0 Lyso-PC values in AGS individuals (0.43μM [0.37-0.48]) was higher than that seen in controls (0.21μM [0.21-0.21]), but lower than X-ALD individuals (0.72μM [0.59-0.84])(p<0.001). Fourteen of 19 children had elevated expression of IFN signaling on blood cards relative to controls (Sensitivity 73.7%, 95%CI 51-88%, Specificity 95%, 95% CI 78-99%) including an individual with delayed disease presentation (36months of age). All five AGS patients with negative IFN signature at birth had RNASEH2B mutations. Consistency of agreement between IFN signature in neonatal and post-natal samples was high (0.85).

Conclusion: This suggests that inflammatory markers in AGS can be identified in the newborn period, before symptom onset. Additionally, since C26:0 Lyso-PC screening is currently used in X-ALD newborn screening panels, clinicians should be alert to the fact that AGS infants may present as false positives during X-ALD screening.

Figure 1. IFN signaling genes in newborn blood spots and post natal samples in AGS versus controls

Interferon signaling gene score (IFN signature), calculated in each individual using the median of the Z scores of the 6 genes in previously published scores (see methods). The IFN signature was considered positive (IFN high) if their value was ≥1.96 (>98centile). IFN signature was elevated in a majority of neonatal samples and correlated with post-natal signatures where available. * post-natal signatures were used only for those patients for whom neonatal signatures were available and do not represent the full range of post-natal signatures in the AGS population.

Figure 2. C26:0 lysophosphatidylcholine (LPC) levels (Tier 1 C26:0 LPC and Tier 2 C26:0 LPC) in newborn blood spots from control, AGS affected and ALD affected infants

AGS affected infants have C26:0 LPC levels in the range of requirement for a repeat analysis (p<0.001) in a majority of cases. Second tier analysis is more reliable in discriminating AGS from ALD individuals, but second tier 26:0 LPC in AGS is still above the typical range of controls (p<0.001).