Genetic recombination contributes to the genomic heterogeneity of human immunodeficiency virus type 1 (HIV-1). In the present study, we demonstrate that HIV-1 readily develops resistance to two classes of anti-HIV-1 drugs through in vitro genetic recombination involving large segments of the viral genome. Co-transfection of COS-7 cells with an HIV-1 plasmid (pSUM13) carrying five mutations in the
reverse transcriptase (RT)-encoding region (A62V, V75I, F77L, F116Y, Q151M), conferring resistance to multiple dideoxynucleoside analogs (
ddNs), and another HIV-1 plasmid (pSUM431) carrying five mutations in the
protease-encoding region (V321, L33F, K451, 184V, L89M), conferring resistance to
protease inhibitors such as
KNI-272, readily produced HIV-1 carrying both sets of mutations when propagated in MT-2 cells in the presence of
azidothymidine (AZT) and
KNI-272. The resultant HIV-1 variant was highly resistant to both
ddNs and
KNI-272.
Co-infection of MT-2 cells with HIV-1SUM13 carrying the RT mutations and HIV-1SUM431 carrying the mutations in the
protease also generated HIV-1 with both sets of mutations when cultured with AZT and
KNI-272. We also report here that the problematic artifactual recombination occurring during genetic analyses of heterogeneous
nucleic acid sequences using polymerase chain reaction can be successfully obviated.