Human immunodeficiency virus type 1 (HIV-1) primarily infects CD4+ lymphocytes and macrophages and causes AIDS in humans. Retroviral vectors allowing neomycin phosphotransferase (npt) gene expression were engineered to express 5' sequences of HIV-1 RNA in the antisense or sense orientation and used to transform the human CD4+ lymphocyte-derived MT4 cell line. Cells expressing antisense or sense RNA to the HIV-1 tat mRNA leader sequence, as part of the 3' untranslated region of the npt mRNA, remained sensitive to HIV-1 infection. In contrast, resistance to HIV-1 infection was observed in cells expressing antisense RNA to the HIV-1 primer-binding site or to the region 5' to the primer-binding site as part of the 3' region of the npt mRNA. Cells expressing the tat mRNA leader sequence in the sense orientation as a precise replacement of the 5' untranslated region of npt mRNA were also resistant to HIV-1. These results indicate that sense and antisense approaches can be used to interfere with HIV-1 multiplication.

Retroviral vectors were modified to contain packaging (psi) signals of varying lengths (nucleotides 211-355, 211-565, or 211-1039 of MoMuLV RNA) between the U3-r and U5 sequences of their 5' long terminal repeat (LTR). For the vector MoTN-PR3, containing the full length 211-1039 nucleotide-long psi signal within the 5' LTR, replication, integration, and packaging were almost as efficient as for the original unmodified vector. This result confirmed that the 211-1039 nucleotide-long sequence from the MoMuLV RNA is sufficient and necessary to allow efficient packaging of RNAs. In addition, an important site was revealed where insertion of foreign DNA sequences of up to 829 nucleotides can be made within the 5' LTR, between U3-r and U5 sequences, without affecting viral replication, integration, or packaging.

No abstract