Production of lentiviruses displaying ''early-acting'' cytokines for selective gene transfer into hematopoietic stem cells

RNA-based gene therapy for HIV with lentiviral vector-modified CD34(+) cells in patients undergoing transplantation for AIDS-related lymphoma

AIDS patients who develop lymphoma are often treated with transplanted hematopoietic progenitor cells. As a first step in developing a hematopoietic cell-based gene therapy treatment, four patients undergoing treatment with these transplanted cells were also given gene-modified peripheral blood-derived (CD34(+)) hematopoietic progenitor cells expressing three RNA-based anti-HIV moieties (tat/rev short hairpin RNA, TAR decoy, and CCR5 ribozyme). In vitro analysis of these gene-modified cells showed no differences in their hematopoietic potential compared with nontransduced cells. In vitro estimates of successful expression of the anti-HIV moieties were initially as high as 22% but declined to approximately 1% over 4 weeks of culture. Ethical study design required that patients be transplanted with both gene-modified and unmanipulated hematopoietic progenitor cells obtained from the patient by apheresis. Transfected cells were successfully engrafted in all four infused patients by day 11, and there were no unexpected infusion-related toxicities. Persistent vector expression in multiple cell lineages was observed at low levels for up to 24 months, as was expression of the introduced small interfering RNA and ribozyme. Therefore, we have demonstrated stable vector expression in human blood cells after transplantation of autologous gene-modified hematopoietic progenitor cells. These results support the development of an RNA-based cell therapy platform for HIV.

Recent advances in lentiviral vector development and applications

Lentiviral vectors (LVs) have emerged as potent and versatile vectors for ex vivo or in vivo gene transfer into dividing and nondividing cells. Robust phenotypic correction of diseases in mouse models has been achieved paving the way toward the first clinical trials. LVs can deliver genes ex vivo into bona fide stem cells, particularly hematopoietic stem cells, allowing for stable transgene expression upon hematopoietic reconstitution. They are also useful to generate induced pluripotent stem cells. LVs can be pseudotyped with distinct viral envelopes that influence vector tropism and transduction efficiency. Targetable LVs can be generated by incorporating specific ligands or antibodies into the vector envelope. Immune responses toward the transgene products and transduced cells can be repressed using microRNA-regulated vectors. Though there are safety concerns regarding insertional mutagenesis, their integration profile seems more favorable than that of gamma-retroviral vectors (gamma-RVs). Moreover, it is possible to minimize this risk by modifying the vector design or by employing integration-deficient LVs. In conjunction with zinc-finger nuclease technology, LVs allow for site-specific gene correction or addition in predefined chromosomal loci. These recent advances underscore the improved safety and efficacy of LVs with important implications for clinical trials.

Down-regulation of CXCR4 expression by SDF-KDEL in CD34(+) hematopoietic stem cells: An anti-human immunodeficiency virus strategy

CXCR4 plays an essential role as the first discovered coreceptor for the entry of T cell tropic isolates of HIV-1. Blocking the surface expression of this receptor may be a potential strategy to prevent HIV-1 infection. A lentiviral vector, pLenti6/V5-S-K, expressing a SDF-KDEL fusion protein was constructed and a replication-incompetent lentiviral stock was produced. The lentiviral stock was transduced into CD34(+) hHSC and the transient expression of the recombinant protein, SDF-1, was assayed using indirect immunofluorescence. The surface expression of CXCR4 in CD34(+) hHSC pretreated with different amounts of recombinant lentiviral vectors was detected by flow cytometric analysis. A marked down-regulation of CXCR4 expression in the cells transduced with recombinant lentiviral vectors pLenti6/V5-S-K was observed by flow cytometry with PE-conjugated anti-human CXCR4 monoclonal antibodies which showed the percentages of the inhibition effects of CXCR4-SDF-1 mediated syncytium formation are presented by concentration. P24 antigen levels of cell culture supernatants were detected on the 4th, 7th, and 10th day, with 10(3) TCID50 HIV-1 infected CD34(+) hHSC to evaluate the inhibitory effect of pLenti6/V5-S-K transduction on HIV-1 infection. The cells transfected with pLenti6/V5-S-K had a significant reduction of HIV-1 DP27 infection compared to controls (P<0.05).