On the basis of our previous findings showing that R5 isolates obtained before and after AIDS onset display varying ability to infect target cells in a direct manner [12], divergent utilization of DC-SIGN for trans-infections (Fig. 1) and differences in the V2 PNGS aa160 (Figure 2), we chose to set up head-to-head competition assays to test relative fitness of the viruses in direct and DC-SIGN mediated infections. This evidence concerns the gene CD209 and infection.