after binding to the a-mannosyl-receptor on macrophage plasma membranes. Initial 
studies demonstrate that alglucerase therapy is capable of reversing glucocerebroside 
storage in the patient’s organs. This safe and effective therapy is extremely expensive 
with the annual cost ranging between $100,000-$400,000 per patient depending on the 
treatment regimen and the patient’s weight and is, for this reason, not an option for 
many patients. Therefore alternative treatment forms are necessary. One possible 
treatment modality is ex vivo retrovirus-mediated transfer of the human 
glucocerebrosidase cDNA into hematopoietic long-term repopulating cells of patients 
with Gaucher’s disease followed by infusion of the transduced cells into the patient. 
B. Retrovirus-mediated transduction of the human glucocerebrosidase cDNA into murine 
long-term repopulating marrow cells 
Several investigators have demonstrated efficient transduction of the human 
glucocerebrosidase (GC) cDNA into a substantial fraction of murine long-term 
repopulating marrow cells using retrovirus vectors (14-17). Long-term reconstituted mice 
analyzed up to 8 months after transplantation of transduced marrow contained the intact 
provirus in marrow, spleen and thymus cells at greater than 1 copy per cell, indicating 
effective transduction of long-term repopulating hematopoietic cells. When marrow from 
the primary recipient mice was transplanted into secondary recipient animals, the intact 
provirus genome was detected in marrow, spleen, thymus and macrophages 4 months 
after secondary transplantation. Human GC mRNA was detected in macrophages as 
well as other hematopoietic cells of the animals. The levels of human GC enzyme 
activity in macrophages from marrow and spleen were equal to or greater than the 
endogenous mouse GC activity. Human GC could be precipitated with an antibody 
specific for human GC. Immunohistochemical analysis detected the human GC protein 
in 81% of the macrophages from the transplanted mice. These data indicate that murine 
long-term repopulating marrow cells can be efficiently transduced by retrovirus vectors 
containing the human GC cDNA and that high levels of human GC activity comparable 
with endogenous mouse activity can be observed in the majority of macrophages from 
these long-term reconstituted mice. 
C. Retrovirus-mediated transduction of the neomycinphosphotransferase (neo) and the 
human adenosine deaminase (ADAl gene into canine long-term repopulating marrow 
cells. 
Gene transduction into hematopoietic repopulating cells and long-term gene expression 
in large random bred animals has proven to be more difficult to achieve than in mice. 
One major difference between the experimental models is that the number of marrow 
donors, and therefore marrow cells, is basically unlimited in the inbred murine model, 
while in random bred animals, marrow is only available from one animal, the marrow 
recipient. This would also be the case in human applications. The amount of marrow 
cells available for vector transduction is therefore limited. 
We have established a model for studying retrovirus mediated gene transduction into 
canine hematopoietic progenitor cells. The dog serves as a preclinical model to develop 
procedures which allow gene transduction into hematopoietic repopulating cells and to 
test the safety of these procedures before application of the techniques to humans. Two 
different methods have been used to transduce canine long-term repopulating marrow 
cells (18). The first method consisted of 24 hours cocultivation of marrow cells on 
Recombinant DNA Research, Volume 18 
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