FIG. 2.

The requirement for Nef in HIV-1 replication maps to the V3 loop of gp120. NL4-3-based V3 loop chimeras conferring different tropisms were cultured in activated CD4⁺ primary T lymphocytes as described in Materials and Methods. Results shown are the averages of duplicate growth curves from a representative of eight experiments. Filled squares, nef⁺ HIV-1; open diamonds, nef-deficient HIV-1.