siRNAs, ribozymes and RNA decoys in modeling stem cell-based gene therapy for HIV/AIDS.

Gene therapy strategies for HIV infection require gene transduction of hematopoietic stem cells with effective therapeutic constructs. Here we summarize our studies on anti-HIV ribozymes, RNA decoys and the newly described siRNAs. The therapeutic constructs consisted of an anti-CCR5 ribozyme to down-regulate the HIV-1 cell surface co-receptor and ribozymes targeted to viral mRNAs coding for the tat, rev and env proteins. The RNA decoy targeted rev and the siRNA was directed against a sequence common to rev and tat mRNAs. CD34 hematopoietic progenitor cells were transduced with retroviral or lentiviral vectors containing these constructs. They were differentiated into macrophages in vitro and T cells in vivo in a SCID-hu mouse thymopoiesis model. The transgene-containing macrophages and T cells were found to be phenotypically normal. When challenged in vitro with HIV-1, they showed significant anti-viral resistance. These proof-of-concept studies demonstrated the utility of RNA-based anti-HIV constructs for gene therapy.