Molecular characterization of HIV-1 isolated from a serum collected in 1976: nucleotide sequence comparison to recent isolates and generation of hybrid HIV.

Human immunodeficiency virus type 1 (Z321 designate, HIV-1Z321), the oldest known HIV, was isolated from a serum sample collected in Zaire in 1976 and was molecularly cloned. Restriction enzyme analysis of unintegrated viral DNA revealed the presence of conserved restriction enzyme cleavage sites in the long terminal repeat sequences. Nucleotide sequence analysis of the 3' end of the viral DNA revealed a pattern similar to other HIV-1 isolates described. However, some of the common restriction sites present in other isolates were absent in HIV-1Z321. The extent of differences between HIV-1Z321 and recent isolates from North America and Zaire was 17.86-18.36% on the nucleotide sequence level and 26.5-33.2% difference in the predicted amino acid sequence in the envelope gene. Differences were also noted in 3'-orf (nef: according to HIV gene nomenclature; see Ref. 42) gene and U3 region of the long terminal repeat sequences of HIV-1Z321 and other isolates. Nucleotide sequence of a HIV-1 isolate, 12 years apart from the present isolates, will provide an important time calibration point for the evolutionary divergence of HIV isolates. Hybrid HIV was also generated by transfecting HIV-1Z321 and HIV-1HTLV-III viral DNAs into cells.