An additional factor that may explain the identification of a vaccine/placebo distinction in V2 is the fact that 60% of the CD4 responses detected in a subset of RV144 vaccine recipients were directed against V2 [14], although, paradoxically, these responses were not identified post-infection, suggesting that antigen-specific T cells could possibly have been preferentially infected and deleted [15]. The gene discussed is CD4; the disease is infection.