Efficient gene transfer by a human immunodeficiency virus type 1 (HIV-1)-derived vector utilizing a stable HIV packaging cell line

By transfecting fibroblast cells with an HIV-1-MN molecular clone with a deletion of the major packaging sequence, we have developed a stable HIV-1 packaging cell line, Psi 422. Psi 422 cells form syncytia with CD4-positive cells, correctly express HIV-1 structural proteins. and produce a large amount of mature particles with normal reverse transcriptase activity, Yet these particles, in which RNA was not detected by reverse transcriptase-PCR, are not infectious, When stably transfected with an HIV-1-based retroviral vector, the Psi 422 cell line produces virions capable of transducing CD4-positive cells with high efficiency (up to 10(5) cells per ml), The availability of this stable noninfectious HIV-1 packaging cell line capable of generating high-titer HIV-1 vectors represents a new step toward the use of an HIV-1 delivery system in gene therapy.