Fig. 1.

Experimental design. HIV-1 NL4-3 was serially transferred in MT-2 and MT-4 T-cells in two replicates each. Odd transfers occurred after 3 days, even transfers after 4 days. At each transfer, we infected new T-cells with ∼0.05% of the cell suspension from the previous culture (supplementary fig. S1, Supplementary Material online).