MTB- and CMV-specific CD4 T cells are lost at different rates after HIV infection. (A) The frequency of MTB-specific (black, 5 PPD responding subjects, who remained TB asymptomatic) and CMV-specific memory CD4 T cell responses (gray; n = 6 CMV responding subjects who remained CMV disease free) at 6–12 mo after HIV seroconversion as the percentage of baseline response detected at 3 mo before the first HIV-seropositive follow up in latently infected subjects. The frequency of MTB- or CMV-specific CD4 T cell responses in chronically HIV-infected subjects (median time since HIV infection >3 yr; n = 17) and a HIV⁻ control group (n = 17) is shown in B and C, respectively. The limit of detection is indicated. Memory CD4 T cells were defined by expression of CD27 and CD45RO. IFN-γ⁺ memory CD4 T cells were detected after in vitro stimulation of PBMCs with PPD or whole inactivated CMV virus by intracellular cytokine staining. Statistical analysis was performed using the Mann-Whitney test.