Phenotypic characterization of HIV-specific CD8⁺ T cells during primary HIV infection, in untreated and HAART-treated participants. (A) HIV-specific CD8⁺ T cells were gated based on HIV multimer and CD8 expression. (B-D) Representative phenotypes of HIV-specific CD8⁺ T cells are presented: most HIV-specific CD8⁺ T cells expressed CD27 and CD45RO at baseline during PHI (B); in untreated participants after PHI, HIV-specific CD8⁺ T cells were CD27^+/− CD45RO⁺ (C); and HIV-specific CD8⁺ T cells in HAART-treated participants were CD27⁺ CD45RO^+/− (D).