CD4 and infection: The steady rise of the percentage of GFP-expressing rat CD4 T-cells over the course of the HIV-1R7/3 YU-2 Env GFP infection (Fig. 9A) was sensitive to the addition of the reverse transcriptase inhibitor efavirenz (EFV) 18 h post-challenge, which inhibited viral replication subsequent to first-round infection.