Higher frequencies of CMV-specific CD4⁺ and CD8⁺ T cells are present in subjects experiencing CMV reactivation after SCT.

(A) Higher frequencies of CMV-specific CD8⁺ T cells in patients with early CMV antigenemia. CMV-specific CD8⁺ T cells were measured by HLA-pp65 tetramer staining at a median of day 94 after SCT. Frequencies of CMV-specific CD8⁺ T cells were stratified by the occurrence of early antigenemia, traditionally defined by CMV reactivation prior to day 100 after SCT. Higher frequencies of CMV-specific CD8⁺ T cells were present in individuals who experienced early CMV antigenemia (○, median 2.2%) relative to those subjects who did not (●, median 0.33%) (P = .0002). (B) Frequencies of CMV-specific CD8⁺ T cells in patients stratified by the occurrence of late CMV antigenemia. A trend was noted toward higher frequencies of CMV-specific CD8⁺ T cells in individuals who experienced late CMV antigenemia (○, median 2.4%) relative to those subjects who did not (●, median 0.57%) (P = .06). (C) Higher frequencies of CMV-specific CD4⁺ T cells in patients with early CMV antigenemia. CD4⁺ T-cell responses were assessed using cytokine flow cytometry following stimulation of PBMCs using a mixture of overlapping peptides spanning the entire CMV pp65 protein sequence. The frequency of CMV-specific CD4⁺ T cells was determined by flow cytometry by assessing the simultaneous up-regulation of the CD69 activation marker and production of intracellular TNF-α in CD4⁺ T cells. Higher frequencies of CMV-specific CD4⁺ T cells were present in individuals who experienced early CMV antigenemia (○, median 1.71%) relative to those subjects who did not (●, median 0.75%) (P = .002). All P values attained by the Mann-Whitney test.