Inborn errors of metabolism are genetic disorders due to impaired activity of enzymes, transporters, or cofactors resulting in accumulation of abnormal metabolites proximal to the metabolic block, lack of essential products or accumulation of by-products. Many of these disorders have serious clinical consequences for affected neonates, and an early diagnosis allows presymptomatic treatment which can prevent severe permanent sequelae and in some cases death. Expanded newborn screening for these diseases is a promising field of targeted metabolomics. Here we report the application, between 2007 and 2014, of this approach to the identification of newborns in southern Italy at risk of developing a potentially fatal disease. The analysis of amino acids and acylcarnitines in dried blood spots by tandem mass spectrometry revealed 24 affected newborns among 45 466 infants evaluated between 48 and 72 hours of life (overall incidence: 1 : 1894). Diagnoses of newborns with elevated metabolites were confirmed by gas chromatography-mass spectrometry, biochemical studies, and genetic analysis. Five infants were diagnosed with medium-chain acyl CoA dehydrogenase deficiency, 1 with methylmalonic acidemia with homocystinuria type CblC, 2 with isolated methylmalonic acidemia, 1 with propionic acidemia, 1 with isovaleric academia, 1 with isobutyryl-CoA dehydrogenase deficiency, 1 with beta ketothiolase deficiency, 1 with short branched chain amino acid deficiency, 1 with 3-methlycrotonyl-CoA carboxylase deficiency, 1 with formimino-transferase cyclodeaminase deficiency, and 1 with cystathionine-beta-synthase deficiency. Seven cases of maternal vitamin B₁₂ deficiency and 1 case of maternal carnitine uptake deficiency were detected. This study supports the widespread application of metabolomic-based newborn screening for these genetic diseases.

Mucopolysaccharidosis type I is a lysosomal disease due to mutations in the IDUA gene, resulting in deficiency of α-L-iduronidase and accumulation of glycosaminoglycans (GAGs). Bone marrow transplantation and enzyme replacement are two therapies considered only moderately successful for affected patients, making the development of novel treatments necessary. We have previously shown the efficacy of lentivirus-mediated gene transfer to correct patient fibroblasts in vitro. Here we tested lentiviral-IDUA vector gene therapy in vivo on a murine MPS I model. Eight- to 10 week-old mice were injected with increasing lentiviral doses via the tail vein and analyzed 1 month after treatment. A single injection of lentiviral-IDUA vector resulted in transgene expression in several murine tissues, with the highest level reached in liver and spleen. Expression of 1% normal activity was sufficient in treated animals to normalize the GAG level in urine, liver, and spleen and was able to reduce the GAG level in kidney, heart, and lung. Polymerase chain reaction assays showed integration of the viral genome only in liver and spleen of treated animals, suggesting that the correction of the pathology in other tissues was due to secretion into the plasma by liver and spleen and uptake of corrective enzyme by distant tissues. Long-term (6 months) analysis showed the presence of enzyme-specific antibodies and the loss of enzyme activity and vector sequence in the target tissue, suggesting that the transgene-specific immune response interfered with long-term therapeutic correction and led to clearance of transduced cells. In conclusion, our results show the promising potential and the limitations of lentiviral-IDUA vector-mediated gene therapy in an in vivo model.