Reversions improve viral replication. A. 50 × 103SupT1 T cells were infected with 2500 pg CA-p24 and virus spread was measured for 14 days. B. gp120 and CA-p24 contents in virus were measured by ELISA. The gp120 amounts were standardized for CA-p24 input and the gp120 contents of mutants in the respective fractions are given as percentages of the wt gp120 contents (arbitrarily set at 100). The results are representative for results from at least three independent experiments.