BACKGROUND

Mucopolysaccharidosis type I (MPS I) is an inherited lysosomal storage disorder (LSD) caused by recessive mutations in the α-L-iduronidase (IDUA) gene. Enzyme replacement therapy (ERT) utilizing terminal mannose-6-phosphate (M6P)-carrying N-glycans attached to therapeutic enzymes produced by mammalian cell lines has been clinically applied to several LSDs. Recent studies suggested an unidentified delivery pathway mediated by sialic acid-containing N-glycans. However, more economical platform development is required to produce large quantities of recombinant enzymes. Transgenic silkworms have been established as low-cost systems for expressing recombinant glycoproteins. Microbial endo-β-N-acetylglucosaminidases (ENGases) enable the transglycosylation of N-glycans to other types.

METHODS

We purified recombinant human IDUA from IDUA transgenic silkworm cocoons and performed ENGase-mediated transglycosylation. Furthermore, we performed intravenous enzyme replacement therapy in a Japanese macaque MPS I non-human primate model carrying a homozygous IDUA missense mutation.

RESULTS

Here we show the establishment of IDUA transgenic silkworms and purification of recombinant human IDUA from cocoons. As M6P- and sialic acid-containing N-glycans are not attached to purified hIDUA, we perform ENGase-mediated transglycosylation to obtain hIDUAs with M6P- and sialic acid-containing N-glycans (neoglyco-hIDUAs). Furthermore, we perform intravenous neoglyco-hIDUA replacement therapy in MPS I non-human primate model and succeed in improving the clinical signs and reducing the urinary glycosaminoglycan (GAG) levels.

CONCLUSIONS

These glycotechnologies using transgenic silkworms and ENGases are expected to serve as platforms for developing therapeutic glycoproteins.