Attachment II - Page 12 
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(a) What cell types have been infected with the retroviral 
vector preparation? Which cells, if any, produce 
infectious particles? 
(b) H cw stable are the retroviral vector and the resulting 
provirus against loss, rearrangement, recombination, or 
nutation? What information is available cn hew rruch 
rearrangement or recombination with endogenous or other 
viral sequences is likely to occur in the patient's 
cells? What steps have been taken in designing the 
vector to minimize instability or variation? What 
laboratory studies have been performed to check for 
stability, and what is the sensitivity of the analyses? 
(c) What laboratory evidence is available concerning poten- 
tial harmful effects of the treatment, e.g. , development 
of neoplasia, harmful nutations, regeneration of 
infectious particles, or irmune responses? What steps 
have been taken in designing the vector to minimize 
pathogenicity? What laboratory studies have been 
performed to check for pathogenicity, and vhat is the 
sensitivity of the analyses? 
(d) Is there evidence from animal studies that vector DNA 
has entered untreated cells, particularly germ line 
cells? What is the sensitivity of the analyses? 
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