Mona Abaoui

Tandem mass spectrometry multiplex analysis of methylated and non-methylated urinary Gb3 isoforms in Fabry disease patients.

BACKGROUND Fabry disease is a lysosomal storage disorder leading to the accumulation of glycosphingolipids in biological fluids and tissues. Globotriaosylceramide (Gb3) and globotriaosylsphingosine (lyso-Gb3) are currently used for Fabry screening and diagnosis. However, these biomarkers are not always increased in Fabry patients with residual enzyme activity. We recently identified 7 urinary methylated Gb3-related isoforms. The aims of this study were (1) to develop and validate a novel LC-MS/MS method for the relative quantification of methylated and non-methylated Gb3 isoforms normalized to creatinine, (2) to evaluate these biomarkers in Fabry patients and healthy controls, and (3) to assess correlations between biomarker urinary excretion with age, gender, treatment and genotype of patients. METHODS Urine samples from 150 Fabry patients and 95 healthy controls were analyzed. Samples were purified and injected in the tandem mass spectrometer working in positive electrospray ionization. Relative quantification was performed for 15 methylated and non-methylated Gb3 isoforms. RESULTS Significant correlations (p<0.001) were established between Gb3 isoform concentrations, gender and treatment. Five patients with the late-onset cardiac mutation p.N215S showed abnormal concentrations of methylated Gb3 isoforms compared to their non-methylated homologues. CONCLUSIONS Methylated Gb3 isoforms might be helpful urinary biomarkers for Fabry patients with late-onset cardiac variant mutations.

Lentivector Iterations and Pre-Clinical Scale-Up/Toxicity Testing: Targeting Mobilized CD34+ Cells for Correction of Fabry Disease

Fabry disease is a rare lysosomal storage disorder (LSD). We designed multiple recombinant lentivirus vectors (LVs) and tested their ability to engineer expression of human α-galactosidase A (α-gal A) in transduced Fabry patient CD34+ hematopoietic cells. We further investigated the safety and efficacy of a clinically directed vector, LV/AGA, in both ex vivo cell culture studies and animal models. Fabry mice transplanted with LV/AGA-transduced hematopoietic cells demonstrated α-gal A activity increases and lipid reductions in multiple tissues at 6 months after transplantation. Next we found that LV/AGA-transduced Fabry patient CD34+ hematopoietic cells produced even higher levels of α-gal A activity than normal CD34+ hematopoietic cells. We successfully transduced Fabry patient CD34+ hematopoietic cells with “near-clinical grade” LV/AGA in small-scale cultures and then validated a clinically directed scale-up transduction process in a GMP-compliant cell processing facility. LV-transduced Fabry patient CD34+ hematopoietic cells were subsequently infused into NOD/SCID/Fabry (NSF) mice; α-gal A activity corrections and lipid reductions were observed in several tissues 12 weeks after the xenotransplantation. Additional toxicology studies employing NSF mice xenotransplanted with the therapeutic cell product demonstrated minimal untoward effects. These data supported our successful clinical trial application (CTA) to Health Canada and opening of a “first-in-the-world” gene therapy trial for Fabry disease.

Tandem Mass Spectrometry Quantitation of Lyso‐Gb3 and Six Related Analogs in Plasma for Fabry Disease Patients

Fabry disease is an X‐linked lysosomal storage disorder, caused by a deficit in α‐galactosidase A enzyme activity, leading to the storage of sphingolipids such as globotriaosylsphingosine (lyso‐Gb3), globotriaosylceramide (Gb3), and galabiosylceramide (Ga2) in organs, tissues and biological fluids. A recent metabolomic study performed in plasma revealed lyso‐Gb3 analogs as novel Fabry disease biomarkers. These molecules correspond to lyso‐Gb3 with different chemical modifications on the sphingosine chain (−C2H4, −H2, +O, +H2O, +H2O2, and +H2O3). An ultra‐performance liquid chromatography tandem mass spectrometry (UPLC‐MS/MS) method was developed and validated for the multiplex analysis of lyso‐Gb3 and its 6 analogs in plasma. The samples are prepared by solid phase extraction using mixed‐mode strong cation exchange (MCX) cartridges. An in‐house synthesized N‐glycinated lyso‐Gb3 derivative was used for the internal standard. The limits of detection (LODs) measured for lyso‐Gb3 and its analogs ranged from 0.06 to 0.29 nM.

High‐Risk Screening for Fabry Disease: Analysis by Tandem Mass Spectrometry of Globotriaosylceramide (Gb3) in Urine Collected on Filter Paper

Fabry disease is a complex, panethnic lysosomal storage disorder. It is characterized by the accumulation of glycosphingolipids in tissues, organs, the vascular endothelium, and biological fluids. The reported incidence in different populations is quite variable, ranging from 1:1400 to 1:117,000. Its complexity lies in the marked genotypic and phenotypic heterogeneity. Despite the fact that it is an X‐linked disease, more than 600 mutations affect both males and females. In fact, some females may be affected as severely as males. The purpose of this protocol is to focus on the high‐risk screening of patients who might have Fabry disease using a simple, rapid, non‐invasive high performance liquid chromatography‐tandem mass spectrometry (HPLC‐MS/MS) method for urinary globotriaosylceramide (Gb3) analysis. Urine filter paper samples are easily collected at home by patients and sent by regular mail. This method has been successfully used for high‐risk screening of patients with ophthalmologic manifestations and in an on‐going study for high‐risk screening of Fabry disease in patients with chronic kidney diseases.

Analysis of globotriaosylceramide (Gb3) isoforms/analogs in unfractionated leukocytes, B lymphocytes and monocytes from Fabry patients using ultra-high performance liquid chromatography/tandem mass spectrometry

Fabry disease is an X-linked lysosomal storage disorder with marked variability in the phenotype and genotype. Glycosphingolipids such as globotriaosylceramide (Gb3) isoforms/analogs, globotriaosylsphingosine (lyso-Gb3) and analogs, and galabiosylceramide (Ga2) isoforms/analogs may accumulate in biological fluids and different organs. The aims of this study were to: 1) develop/validate a novel UHPLC-MS/MS method for relative quantitation of Gb3 in leukocytes (unfractionated white blood cells), B lymphocytes and monocytes; 2) evaluate these biomarkers in a cohort of Fabry patients and healthy controls; and 3) assess correlations between these biomarkers, treatment and genotype. Whole blood, plasma and urine samples from 21 Fabry patients and 20 healthy controls were analyzed. Samples were purified by liquid-liquid extraction and analyzed by UHPLC-MS/MS in positive electrospray ionization. Methylated Gb3 isoforms were detected, showing that a methylation process occurs at the cellular level. Our results show that there were no significant differences in the distribution of the different Gb3 isoforms/analogs in blood cells between Fabry patients and healthy controls. In leukocyte, Gb3[(d18:1)(C14:0)], Gb3[(d18:1)(C16:0)], Gb3 [(d18:1)(C16:0)]Me, Gb3 [(d18:1)(C16:1)], Gb3 [(d18:1)(C18:0)], Gb3 [(d18:1)(C18:1)], Gb3 [(d18:1)(C20:1)], Gb3 [(d18:1)(C24:2)], Gb3 [(d18:1)(C26:1)] and total Gb3 allowed good discrimination between male Fabry patients and male controls, patients having higher biomarker levels than controls. Regarding B lymphocytes and monocytes, the same tendency was observed without reaching statistical significance. A positive concordance between mutation types and biomarker levels in white blood cells was established. Our results might provide a deeper mechanistic comprehension of the underlying biochemical processes of Gb3 biomarkers in white blood cells of Fabry patients.

Fabry Disease Biomarkers: Analysis of Urinary Lyso‐Gb3 and Seven Related Analogs Using Tandem Mass Spectrometry

Fabry disease is an X‐linked lysosomal storage disorder caused by the absence or reduction of the enzyme α‐galactosidase A activity. Currently, globotriaosylsphingosine (lyso‐Gb3) and globotriaosylceramide (Gb3) are used as biomarkers to diagnose and monitor Fabry patients. However, recent metabolomic studies have shown that several glycosphingolipids are also elevated in biological fluids of affected patients and may be related to disease manifestations. This unit describes a multiplex methodology targeting the analysis of urinary lyso‐Gb3 and seven structurally related analogs. A solid‐phase extraction process is performed, then lyso‐Gb3 and its analogs are analyzed simultaneously with an internal standard by ultra‐performance liquid chromatography (UPLC) coupled to a tandem mass spectrometry (MS/MS) system. This methodology can be useful for the diagnosis of Fabry patients, including patients with cardiac variant mutations, but also to monitor the efficacy of therapeutic interventions, considering that lyso‐Gb3 analogs are more elevated than lyso‐Gb3 itself in urine.

High‐Risk Screening of Fabry Disease: Analysis of Fifteen Urinary Methylated and Non‐Methylated Gb3 Isoforms Using Tandem Mass Spectrometry

Fabry disease is a multisystemic, X‐linked lysosomal storage disorder caused by mutations in the GLA gene, leading to α‐galactosidase A deficiency and resulting in the accumulation of glycosphingolipids in different tissues and biological fluids. Glycosphingolipid biomarkers, such as globotriaosylceramide (Gb3) isoforms, globotriaosylsphingosine (lyso‐Gb3) and related analogs, and galabiosylceramide (Ga2) isoforms and analogs, are found to be abnormally increased in urine and in plasma of Fabry patients and have the potential to be used as specific biomarkers of the disease. This unit presents a protocol for the relative quantification of fifteen urinary isoforms of Gb3 analyzed simultaneously with creatinine by ultra‐performance liquid chromatography (UPLC) coupled to tandem mass spectrometry (MS/MS). In order to purify urine samples, a liquid‐liquid extraction is performed and samples are analyzed by MS/MS in positive electrospray ionization mode. These biomarkers are useful for screening, diagnosis, and long‐term monitoring of Fabry disease patients. We have shown that the methylated Gb3 isoforms are particularly useful for screening Fabry patients who present with late‐onset cardiac variant mutations.