Two-step gene transfer using an adenoviral vector carrying the CD4 gene and human immunodeficiency viral vectors.

Human immunodeficiency virus-1 (HIV-1) belongs to the lentivirus subfamily of retroviruses and has several interesting features, including T cell tropism and the ability to infect nondividing cells. Replication-incompetent HIV vectors were developed and were shown to be capable of targeted gene transfer into CD4+T cells. This strict T cell tropism may be important for the development of gene therapy of acquired immunodeficiency syndrome (AIDS), but it hampers the use of the HIV vector for other gene transfer applications. To expand the host range of the HIV vector, we established the two-step gene transfer system, which allows us to transduce non-T cells stably. In the first step, the CD4 gene was introduced into target cells using a replication-defective adenoviral vector. Transient but high-level expression of CD4 molecules was detected in both adherent and floating cells. In the subsequent step, the cells were incubated with HIV vectors. Stable integration of the HIV vector was demonstrated in cells transduced with the adenoviral vector. These results indicate that transient expression of CD4 molecules by the adenoviral vector is sufficient to render non-T cells susceptible to HIV-mediated gene transfer. This two-step gene transfer strategy may be used as a general method to transduce various types of human cells stably including nondividing cells.