Lentivirus Vectors Using Human and Simian Immunodeficiency Virus Elements

Abstract

Lentivirus vectors based on human immunodeficiency virus (HIV) type 1 (HIV-1) constitute a recent development in the field of gene therapy. A key property of HIV-1-derived vectors is their ability to infect nondividing cells. Although high-titer HIV-1-derived vectors have been produced, concerns regarding safety still exist. Safety concerns arise mainly from the possibility of recombination between transfer and packaging vectors, which may give rise to replication-competent viruses with pathogenic potential. We describe a novel lentivirus vector which is based on HIV, simian immunodeficiency virus (SIV), and vesicular stomatitis virus (VSV) and which we refer to as HIV/SIVpack/G. In this system, an HIV-1-derived genome is encapsidated by SIVmac core particles. These core particles are pseudotyped with VSV glycoprotein G. Because the nucleotide homology between HIV-1 and SIVmac is low, the likelihood of recombination between vector elements should be reduced. In addition, the packaging construct (SIVpack) for this lentivirus system was derived from SIVmac1A11, a nonvirulent SIV strain. Thus, the potential for pathogenicity with this vector system is minimal. The transduction ability of HIV/SIVpack/G was demonstrated with immortalized human lymphocytes, human primary macrophages, human bone marrow-derived CD34+ cells, and primary mouse neurons. To our knowledge, these experiments constitute the first demonstration that the HIV-1-derived genome can be packaged by an SIVmac capsid. We demonstrate that the lentivirus vector described here recapitulates the biological properties of HIV-1-derived vectors, although with increased potential for safety in humans.

High efficiency lentiviral gene delivery in non‐dividing cells by deoxynucleoside treatment

“…Gene transfer into macrophages by lentiviral vectors has been described previously1, 5–7, but a low recovery of transgene‐positive macrophages was observed1, 5–7. Similarly, we have seen a low basal level of transduction in macrophages transduced with HIV‐based vectors.…”

“…The recent development of lentivirus‐based vectors has broadened the spectrum of cell types susceptible to gene transfer, including certain non‐dividing cell types, such as brain, retina, muscle, and macrophages1–7. In most cases, however, the percentage of cells expressing the lentiviral‐delivered gene remains quite low.…”

Functional analysis of gammaretroviral vector transduction by quantitative PCR

“…The remaining cells were used for DNA and mRNA assays. EGFP titres were calculated as previously described 22 using the following formula: titre = (F × C 0 /V) × D; where F is the frequency of EGFP + cells determined by flow cytometry; C 0 is the total number of infected target cells; V is the inoculum volume; and D is the virus dilution factor.…”

Vectors derived from the human immunodeficiency virus HIV-1

“…After the polyproteins, Gag and Gag/Pol, are cleaved by the viral protease, mature particles become fully infectious. In currently available lentiviral vectors, gag/pol are not present in the transfer construct, but are provided in trans by a packaging construct (56,57). Thus, once the transfer vector is integrated in the host cell, its inability to direct production of gag/pol ensures that there will be no subsequent viral progeny.…”