A genetically engineered spleen necrosis virus-derived retroviral vector that displays the HIV type 1 glycoprotein 120 envelope peptide

We reported that SNV-derived retroviral vectors, which display single-chain antibodies on the viral surface, enable cell type-specific gene delivery i nto various human cells. In particular, the SNV cell type-specific gene del ivery vector system appears to be well suited to transduce genes into cells of the human hematopoietic system (Jiang et al, J. Virol, 72:10148-10156, 1998), Here, we report the construction of SNV vector particles that displa y the complete gp120 surface unit of the envelope protein of human immunode ficiency virus type 1 (HIV-1) on the viral surface. The complete gp120-codi ng region of a T cell-tropic HIV-1 strain (LAI/BRU) was fused to a short pe ptide spacer coding region [(Gly(4)Ser)(3)] linking it to the SNV TM-coding region. The corresponding protein was expressed as a single 145-kDa peptid e as expected. This peptide was nontoxic and could be stably expressed in d og D17 SNV-derived packaging cells. Particles harvested from stable packagi ng lines infected CD4(+) human hematopoietic cells with titers exceeding 10 (5) CFU/ml supernatant tissue culture medium, Titers in other, CD4(-) cell lines expressing various coreceptors of HIV-1 were 100-fold lower than tite rs obtained in CD4(+) cells. Specificity of infection was demonstrated by a ntibody inhibition assays or by preincubating cells with SDF-1 alpha, the l igand, which binds to the CXCR4 coreceptor, to which this gp120 binds. Our data indicate that binding of the HIV-1 gp120 to either CD4 or CXCR4 is suf ficient to enable infection of human cells with SNV vector particles.