Isolation and Characterization of Two Divergent Infectious Molecular Clones of HIV Type 1 Longitudinally Obtained from a Seropositive Patient by a Progressive Amplification Procedure

Isolation of infectious molecular clones has been valuable to our understanding of HIV-1-induced pathogenesis. Two infectious molecular clones of HIV-1 were isolated longitudinally from a seropositive subject at different stages of the disease, using a standard bacteriophage lambda vector and a novel progressive amplification procedure. We found the progressive amplification procedure was simpler and more specific than the conventional plaque hybridization assay. The two infectious HIV-1 clones had distinct cell tropism and cytopathic properties. The HIV-1 clone obtained at the asymptomatic stage of the disease was macrophage tropic and had a non-syncytium-inducing property. In contrast, the HIV-1 clone obtained at the stage of AIDS development was dual tropic for T cells and macrophages and induced syncytia. A detailed analysis of the restriction sites of the two clones showed 9 of 21 sites to be unique. These unique restriction sites were predominantly localized in the envelope region. Furthermore, the nucleotide sequence analysis of the entire gp120 region supported the results from the restriction analysis and showed that these two clones are closely related, and the differences are restricted to the variable domains. The difference in amino acid sequences in the V₃ region may explain the observed differences in T cell tropism and syncytium-inducing properties. Availability of two distinct infectious molecular clones from the same patient at different stages of the disease may be useful in studies on the mechanism of HIV-1 pathogenesis.