FIG. 1.

Scheme of passages of HIV-1 clones subjected to plaque-to-plaque transfers in MT-4 cells. Clonal populations (HIV-1 isolated from individual plaques) are depicted as filled squares. The experimental procedures and the origins of natural HIV-1 isolate S61 and clones B1 to K1 are given in reference 78 and in Materials and Methods. HIV-1 clones are indicated by letters followed by a number which gives the total number of plaque-to-plaque transfers undergone by the clone. Infectious virus could not be rescued from viral populations B15, E13, G7, H13, and J15 as described in reference 78.