Intracellular immunization against SIVmac utilizing a hairpin ribozyme

A hairpin ribozyme targeting the 3' LTR region (9456) of SIVmac238 was cloned into a murine retroviral vector. This target sequence is conserved among various SIV, as well as most HIV-2, strains. The ribozyme cassette is driven from a polymerase III promoter, that of the human tRNAval gene. Hybrid human B-/T-cell lines (CEM/174) were transduced with the retroviral constructs and selected for G418 resistance. Cells stably expressing the 9456 ribozyme exhibited long-term resistance to infection by a pathogenic molecular clone of SIV and two strains of HIV-2. The ribozyme was also able to effectively reduce the proviral DNA burden. Its efficient protection against SIV/HIV-2 infection constitutes an important step toward evaluating ribozyme gene therapy in a primate model.