underway. 
Precl ini cal : 
Vector construction as described in Section I.B.I.a. is carried out in E. 
col i K12 under PI conditions as described and outlined in Guidelines for 
Research Involving Recombinant DNA Molecules (Aug 1982. Appendix G II-A). 
Transfer and subsequent handling of vector DNA in mammalian cells are done 
under either PI or P2 conditions. Since our vectors contain less than 2/3 of 
the viral genome, the cells can be handled under PI conditions when helper 
virus contamination has been excluded (see Guidel ines Section III B-3, Section 
III C. Appendix G II-B). Producer cell lines (viz.. S3A) are handled under 
additional safety procedures as outlined in the safety section. 
Infection: 
Recipient marrow can be obtained in the standard fashion. Infection would 
be done under PI conditions and the recipient marrow would be processed in 
facilities where no other cells or supernatant are being handled. The 
Infection should be carried out by someone who has not had known contact 
(immediately preceeding the procedure) with transmissible agents or 
experimental animals. All equipment used after the bone marrow cells are 
exposed to the vector should be disposed of or sterilized as described for PI 
containment. 
Post Infection: 
SCID patients cannot mount an immune response. Therefore, they are 
particularly susceptible to infection. If no viremia occurs in the patient, 
then there is essentially no risk to the immune-competent individuals around 
the patient. The issue is the need to protect the patient. Again the question 
arises, will a low level of replication-competent murine virus produce a 
viremia in the patient which could then: a) be dangerous to the patient: b) 
be potentially dangerous for health care workers and others around the patient: 
[70] 
Recombinant DNA Research, Volume 12 
