allergic reaction may occur. Risks associated with product injections include local pain, 
inflammation, erythema, swelling, itching, tenderness, skin discoloration, skin breakdown, 
regional lymphadenopathy, and possibly even granuloma formation at the injection site. 
Serious inflammation is not anticipated; however, should this occur, symptomatic treatment 
will be promptly provided. Other clinical manifestations that could result from product 
administration include fever and chills, diaphoresis, gastrointestinal distress, allergic reactions 
which may include rash, decrease in blood pressure, shortness of breath and/or syncope, and 
remotely, anaphylaxis. 
There are several theoretical safety concerns related to the use of retrovirally vector-mediated 
gene transfer 14 . These are summarized in Section 5.1 through 5.5. 
5.1 Production of Replication-Competent Virus Through Recombination 
The risk of producing replication-competent retrovirus through recombination is remote 
because (1) All known human endogenous retroviruses have multiple disruptions in their 
coding sequences 15 , and Southern blot analysis of human genomic DNA, probed with the 
HTV-1 env gene, has failed to demonstrate any significant homology; (2) The canine 
packaging cell utilized in HTV-IT (V) production has been engineered to minimize the 
possibility of generating replication-competent retrovirus; (3) Due to the split genome 
approach to production of the packaging cell line, it can be predicted that three separate 
recombination events would be required in order to produce a replication-competent virus 16 ; 
(4) A minimal number of cell doublings will take place in the manufacturing process; and (5) 
Quality Control testing using the Mus dunni cocultivation procedure and the S + L- extended 
assay to detect amphotropic and xenotropic retroviruses will be performed on HTV-IT (V) 
prior to Quality Control release for injection. 17 
5.2 Malignancy Caused by Insertional Mutagenesis 
From a theoretical standpoint, approximately four to five specific mutations are likely required 
within a cell to cause malignant transformation 18 . The risk of potential malignant 
transformation has been assessed by tumorigenicity studies conducted in nude mice and 
immunosuppressed suckling mice, and by transformation studies in soft agar using cells 
expressing the HIV-1 UlBenv/rev retroviral construct No evidence of tumor formation in 
nude and suckling mice or transformation in soft agar using fibroblasts expressing the HIV-1 
ENV/REV proteins has been observed. 
5.3 Contamination and/or Mutation of Germ Cells 
5.3.1 This risk of germ line transmission is viewed as unlikely due to the non-replicating 
nature of the vector. Further, PCR analyses of sperm samples from male Rhesus 
monkeys and HIV- 1 -infected chimpanzees after treatment with autologous cells 
expressing the HTV-1 MBenv/rev retroviral construct have shown no indication of 
transfer of HTV-IT (V) into the germ line tissues of these animals. Additional studies in 
mice have detected no evidence of HTV-1 DNA in testicular tissue taken from mice 
injected with retroviral vector bearing the HTV-1 IHBenv/rev construct. 
5.3.2 Although it is considered unlikely based on the above animal studies, HTV-IT (V) does 
have the theoretical potential to alter germline genes. The risk to a future child is 
unknown and information from animal studies may or may not predict what will 
happen in humans. Participants in this study should make every effort to avoid 
pregnancy (see Sections 3.2.5 and 3.3.2 and Procedures (B) under Informed Consent). 
If pregnancy occurs, a discussion will be held with the Principal Investigator 
^Cometta K. et at., Human Gene Therapy, 2:5-14, 5-15, (1991). 
Abraham, G.N. and Khan, A.S., Clin. Immunol. & Immunopath., 56:1-8 (1990). 
^Miller, D.A., Human Gene Therapy, 1:5-14 (1990). 
^Bassin, R.H., et al., Int. J. Cancer, 6:95-107 (1970). 
^Fearon, E., and Vogelstein, B., Cell, 61:759-67 (1990). 
Recombinant DNA Research, Volume 18 
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