In a clinical study (30), five patients were treated with infusions of tumor- 
infiltrating lymphocytes which had been marked with a neo gene containing 
retrovirus vector (LNL6) which is similar to the vector LgGC which will be used 
in this study. Extensive safety studies were carried out including S + L- assays for 
xenotropic and amphotropic infectious viruses, polymerase-chain-reaction analysis 
for the presence of the amphotropic helper virus 4070A envelope genes and 
reverse transcriptase assays. No safety hazards due to gene transduction were 
recognized including the absence of infectious virus in the infused lymphocytes 
and in the patients after infusion. So far, 21 humans have undergone gene- 
transfer procedures, and no side effects have been observed (41). 
4. Recombination with human endogenous retrovirus sequences 
Another theoretical concern is recombination of the retrovirus vector with human 
endogenous retrovirus sequences, leading to the production of a replication- 
competent human retrovirus. Again, the probability of this occurring appears 
small. No replication-competent human endogenous retrovirus has ever been 
isolated and all known sequences have deletions and frameshift mutations in the 
virus genes. The sequences defective in human endogenous retroviruses (namely 
gag, pol, and env), are the sequences deleted from the LgGC vector, so LgGC is 
unable to provide the needed sequences to restore function to human 
endogenous retrovirus sequences. Also, there is no homology known between the 
LgGC vector and the human retrovirus sequences, so that homologous 
recombination is not expected. In addition, variation in the structure of these 
human and murine virus sequences, such as tRNA binding sites, makes the 
likelihood of successful recombination extremely small. 
These expectations have been borne out in preclinical and clinical practice. 
Recombination between MLV and human endogenous retrovirus sequences has 
not been detectable in primate cells in vitro or in vivo. This question was 
specifically addressed in the LNL6 TIL human gene transfer clinical trial. After 
retrovirus insertion, reverse transcriptase (RT) assays have never detected RT 
activity. 
In summary, the gene transduction studies proposed in this protocol should 
produce minimal, if any, risk to the patient, no risk to other patients, and no risk 
to health care personnel. 
Objectives 
A. To investigate the efficiency and safety of transducing the human glucocerebrosidase 
cDNA into G-CSF mobilized, CD34 enriched peripheral blood repopulating cells from 
patients with Type 1 Gaucher’s disease by retrovirus-mediated gene transfer. 
B. To determine the extent of long-term persistence of transduced peripheral blood 
repopulating cells in Gaucher’s disease patients not receiving prior myeloablation. 
C. To investigate whether the human glucocerebrosidase cDNA is expressed sufficiently to 
improve the disease. 
Recombinant DNA Research, Volume 18 
[671] 
