A Genetically Engineered Spleen Necrosis Virus-Derived Retroviral Vector That Displays the HIV Type 1 Glycoprotein 120 Envelope Peptide

Abstract

We reported that SNV-derived retroviral vectors, which display single-chain antibodies on the viral surface, enable cell type-specific gene delivery into various human cells. In particular, the SNV cell type-specific gene delivery 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 display the complete gp120 surface unit of the envelope protein of human immunodeficiency virus type 1 (HIV-1) on the viral surface. The complete gp120-coding region of a T cell-tropic HIV-1 strain (LAI/BRU) was fused to a short peptide spacer coding region [(Gly₄Ser)₃] linking it to the SNV TM-coding region. The corresponding protein was expressed as a single 145-kDa peptide as expected. This peptide was nontoxic and could be stably expressed in dog D17 SNV-derived packaging cells. Particles harvested from stable packaging lines infected CD4 + human hematopoietic cells with titers exceeding 105 CFU/ml supernatant tissue culture medium. Titers in other, CD4 - cell lines expressing various coreceptors of HIV-1 were 100-fold lower than titers obtained in CD4 + cells. Specificity of infection was demonstrated by antibody inhibition assays or by preincubating cells with SDF-1 alpha, the ligand, 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 sufficient to enable infection of human cells with SNV vector particles.