Virus competition experiments in PBMC. (A) Two viruses were mixed as indicated on top of the panels, usually in a 1:1 ratio (unless indicated otherwise, see panel B). The composition of the virus mixture was followed by PCR across the Nef region with primers tTA1 and CN1 (see Fig. 1A). The experiment has been repeated 5 times for AS19. Appropriate markers and molecular weight standard (M) are indicated. The identity of the respective PCR fragments is indicated on the right. (B) Competition of HIV-1 and AS19 mixed in three ratios: 10:1, 1:1, 1:10. (C) Competition between the R1 variant and either HIV-1 or AS19. R1 is a 106 nt Nef deletion mutant. The experiment has been repeated twice, with similar results.