Women’s & Children’s Hospital, Adelaide, Australia – Dr. John Hopwood
We have continued a number of projects involving studies to achieve clinically effective enzyme replacement (ERT) for lysosomal storage disorders (LSD) that affect the central nervous system (CNS). During 1997/1998, The Children’s Medical Research Foundation provided support for specific studies concerned mostly with the development of ERT in MPS-IIID (Sanfilippo) goat. These studies form part of a major program of research to achieve effective therapy for all LSD that have CNS pathology. I have included a general summary of our research that is focused to achieve this most important goal. The National Health and Medical Research Council of Australia, Women’s & Children’s Hospital Research Foundation, Australian Research Council and Pharming BV continue to support our research focused to overcome this barrier to effective therapy for LSD patients…the prevention of brain pathology. The rate of progress toward this goal is limited only by available funding.
Preliminary studies in collaboration with Dr. Margaret Jones of Michigan State University, where three weekly infusions of recombinant caprine 6-sulfatase into a newborn MPS IIID goat were completed, show that enzyme from circulation could correct storage in liver but not brain. These findings highlight the need to develop methods to enable passage of lysosomal enzymes through the blood/brain barrier into the brain. We have continued to develop technology to enable the efficient production of recombinant enzyme needed for further ERT experiments. Dr. Tom Litjens and Ms. Barbara King have been involved in these studies.
We continue to develop the naturally occurring MPS IIIA mouse model to optimize therapies and understand the pathology leading to the Sanfilippo phenotype. In collaboration with Dr. Pamela Stanley (New York) and Dr. Tommasco Beccari (Perugia), we have identified the mutation that causes the deficiency of sulfamidase in this animal. We have expressed mouse sulfamidase and purified the enzyme to begin studies to optimize ERT. Methods to clinically and biochemically evaluate the pathology present in this model are also under development. Ms. Briony Glidden (Lister Family Ph.D. Scholar), as part of her Ph.D., is using this model to investigate and develop ERT for Sanfilippo patients. Drs. Gouri Yogalingam and Allison Crawley also are involved in these studies.
Our work to produce modified recombinant canine fucosidase that will pass through the blood/brain barrier of the fucosidosis dog continues in collaboration with Dr. Rosanne Taylor (Sydney). Ms. Julie Bielicki is completing her Ph.D. studies with this model. Dr. Don Anson also is involved in these studies.
In collaboration with Dr. Bob Jolly (Palmerston), we have identified a MPS IIIA Huntaway dog. Dr. Gouri Yogalingam, Ms. Viv Muller and Mr. Tony Pollard are working to characterise this model. The Huntaway dog provides another large model to assist development of therapies and improve our understanding of the pathology specifically for Sanfilippo patients and generally for all LSD patients. We have constructed an expression system for the production and purification of human recombinant sulfamidase to be used in ERT investigations with the mouse and dog models.
To enable prediction of clinical severity, we continue to investigate the relationship between mutations and clinical phenotype in MPS IIIA and IIIB (Sanfilippo) patients. To facilitate these studies, we have developed specific substrates and monoclonal antibodies for enzymes involved in these two MPS types. Drs. Birgit Weber and Gouri Yogalingam and Ms. Kelly Perkins have been involved in these studies.
We are using a naturally occurring mannosidosis guinea pig model to investigate and optimize general procedures to transmit enzyme from circulation into the brain. We have identified the mutation causing disease and have established a guinea pig colony. Expression systems for the production of recombinant a-mannosidase have been constructed and purification of enzyme completed to enable ERT studies to begin. Drs. Allison Crawley and Thomas Berg with Ms. Barbara King are working with this model.
We have validated methods to measure amount and type of material stored in the lysosomes of various tissues at different times of development for a number of different LSD (including Sanfilippo). This work has been an extension to technology that we have established to enable screening for the presence of a LSD in all babies at birth. We are investigating the nature of storage-induced pathology at birth and the times/ages when pathology becomes irreversible. Dr. Peter Meikle and Mr. Enzo Ranieri are leaders in our large team dedicated to achieving this goal.