While SL8- and CM9-specific CD8+ T cell responses are both generated during the acute phase of infection [14], [16], the emergence of CTL escape mutants occurs much more rapidly in the Tat-SL8 epitope than it does in Gag-CM9 [14], [17], [18], presumably due to strong functional constraints imposed on the gag gene and the need for extra-epitopic, secondary compensatory mutations to allow effective virus replication [19], [20], [21]. Here, TAT is linked to infection.