2.3 Description of HIV-IT (V) 
2.3.1 HIV-IT (V) is an HIV-1 immunotherapeutic based on retroviral vector-mediated gene 
transfer technology that provides for the delivery of the env and rev gene segments of the 
HIV- 1 IIIB strain directly into subject cells. The retroviral vector containing these genes 
and the vector-producing cell line are subjected to Quality Control testing prior to 
injection into multiple intramuscular (LM) sites. Proteins expressed from these genes and 
presented on the surface of transduced recipient cells may cause substantial stimulation of 
immune responses, in particular the CD8 + CTL response. 
2.3.2 The safety issues regarding retroviral vector gene therapy have been addressed in terms 
of final product testing as well as the molecular design of the vector producer cell line. 
The cell line which produces HIV-IT (V) (DA/N2 MBenv.2C3) has been characterized 
and subjected to numerous quality control analyses, including assays to detect replication- 
competent retroviruses (RCR). 
To increase safety, the DA/N2 IIIBenv.2C3 producer cell line (PCL) is derived from a 
canine cell line with a background genome that contains no detectable sequences 
homologous with the vector or the vector particle structural genes. 
The PCL contains genetically unlinked murine leukemia virus (MLV) structural genes 
(split genome) to reduce the possibility of homologous recombination between the 
provector DNA and the DNA encoding the murine retrovirus structural genes (gag/pol 
and envam) present in the PCL. 13 
In addition, there is reduced sequence homology between the MLV structural genes and 
provector (N2 IIIBenv) DNA because the structural genes in the producer cell line use 
an heterologous transcriptional promoter and termination signals instead of Moloney 
murine leukemia virus long terminal repeats (MoMLV LTRs). Multiple homologous 
recombination events within minimal sequence overlap would be required to generate a 
RCR. 
Several procedures have been used at Viagene to detect RCR in conjunction with a 
commercially available validated extended S + L' test. Vector preparations are tested for 
release using the extended S+L' assay. A sample of post production PCL is tested for 
RCR using a Mus dunni cocultivation procedure. Cocultivation testing on the producer 
cell line before banking, and on the banked cell line have also been carried out. All 
samples tested have yielded uniformly negative results for RCR. When all tests of 
liquid HIV-IT (V) are negative for RCR, HIV-IT (V) undergoes final formulation and 
lyophilization. The lyophilized final product must also pass a battery of quality control 
tests. 
2.4 Preclinical Research and Toxicology/Pharmacology Studies 
2.4.1 Viagene and the scientific staff at the FDA's Center for Biologies (CBER) have worked 
jointly to develop a plan to evaluate the safety and biologic activity of HIV-IT (V). 
Studies have been carried out in mice and non-human primates to address issues of 
safety, toxicity, vector localization, and biologic activity of HIV-IT (V). 
2.4.2 Initial preclinical studies were conducted in a mouse model. The mouse system has 
been used to evaluate the induction of humoral and cellular immune responses 
following direct administration of HIV-IT (V). Briefly, mice were immunized with a 
series of HIV-IT (V) injections and HIV-1 ENV/REV specific CD8 + CTL responses 
were analyzed. 
Representative data from responding mice are shown in Figure 1 where HIV-IT (V) 
injected into BALB/c mice induced a CTL response directed against target cells 
^Miller, Human Gene Therapy, 1:5-14 (1990). 
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