Salivary α-Iduronidase Activity as a Potential New Biomarker for the Diagnosis and Monitoring the Effect of Therapy in Mucopolysaccharidosis Type I

ABSTRACT Although disease progression in Mucopolysaccharidosis I (MPS-1) can be attenuated by hematopoietic cell transplantation (HCT), it is increasingly recognized that residual disease is substantial. Biomarkers that would allow us to evaluate the efficacy of HCT (and upcoming new therapies) in non-hematological tissues are needed. Current biomarkers, including the iduronidase (IDUA) activity in leukocytes, are not suitable for this purpose as they are assessed in tissues of hematological origin and may not reflect enzyme availability in non-hematologic tissues. Saliva is a non-hematological body fluid which can be collected easily and non-invasively. We hypothesized that the extent of recovery of IDUA activity in saliva after HCT could provide better understanding of the penetration of donor derived enzyme into non-hematological compartments. This study in 20 MPS-1 patients shows that the measurement of IDUA activity in saliva is possible and allows diagnosis of IDUA deficiency (p