Safety of retrovirus gene therapy, Temin, 
tially, only very serious, life-threatening genetic diseases should be candidates for this 
therapy. 
Furthermore, given our present state of ignorance of how these vectors will ac- 
tually work in humans, initially only genetic diseases whose primary effect is on bone 
marrow cells or diseases that can be treated by infection of other easily retransplantable 
cells should be treated (Parkman,1986). This requirement will give an opportunity to 
monitor the effects of the infection outside the papent^ For example, this therapy should 
probably first only be tried with patients wimradenine deaminase deficiency, which 
causes a severe combined immunodeficiency dTseSeT 
If the somatic gene therapy of human disease with retrovirus vectors proves safe 
and effective, extension to other very serious single gene human diseases would be war- 
ranted. 
Should this therapy ever be used for conditions that are not fatal such as dwarf- 
ism (Anderson, 1985; Walters, 1986)? If this therapy was proven safe and effective in 
fatal diseases and if its use was safer, cheaper, and more convenient than continued injec- 
tions of growth hormone, then its use would be warranted in such a non-fatal condition 
where it substituted for a less safe therapy. In cases where there is not an alternate 
therapy, the possiblity of later cancer must be evaluated against the benefits of the therapy 
with retrovirus vectors. 
However, as with any powerful medical therapy, there will be desires to use 
retrovirus gene replacement therapy to treat normal individuals to supplement normal 
functions. This desire is in no way different from the present use of hormones to build 
muscles in athletes (Limbird,1985). The questions already raised about the desirability of 
this practice are relevant to the question of the use of retrovirus vectors for potentiation of 
normal functions rather than for theraDv. 
Recombinant DNA Research, Volume 12 [38 7 1 
