Scientific Abstract 
HIV-1 infection causes progressive depletion of CD4 + T lymphocytes and, after a period 
of clinical latency averaging 7-12 years, the clinical syndrome of AIDS in the 
overwhelming majority of patients. The gravity of the expanding pandemic and lack of 
effective treatments continue to spur a search for innovative therapies. Ribozymes are 
potentially therapeutic RNA molecules that contain anti-sense sequences for specific 
recognition, and RNA-cleaving enzymatic activity (11-20). We have shown that human 
T-cell lines and primary peripheral blood human T cells transduced with a hairpin 
ribozyme that cleaves HIV-1 RNA in the 5' leader sequence are intracellularly 
immunized against challenge with cloned and uncloned HIV-1 isolates (7,8,9). Escape or 
resistant virus is not detected after long term culture. The transduced T cells 
persistently express the ribozyme and there are no apparent deleterious effects on cell 
proliferation or long-term viability (9). The ribozyme acts at two steps in the viral 
lifecycle: by cleaving both afferent viral RNA genomes (9) and efferent viral mRNA 
expressed from integrated provirus (7,8,9). In this study, we will evaluate the safety 
and efficacy of ribozyme gene therapy in four to six patients with HIV-1 infection by 
reinfusing autologous CD4 + T cells that have been transduced ex vivo with a retroviral 
vector that expresses the HIV-1 leader sequence ribozyme. The in vivo kinetics and 
survival of ribozyme-transduced cells will be compared by limiting dilution PCR with 
those of a separate aliquot of cells transduced with a control vector (identical except for 
the ribozyme cassette). The level and persistence of ribozyme expression will also be 
assessed. The results will determine whether this ribozyme can protect CD4 + T cells in 
patients with HIV infection and will aid design of future trials of larger scale T cell 
replacement therapy and trials of hematopoietic stem cell gene therapy for HIV disease. 
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Recombinant DNA Research, Volume 18 
