Age-Dependent Association between Low Frequency of CD27/CD28 Expression on pp65 CD8+T Cells and Cytomegalovirus Replication after Transplantation

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Abstract
In this cross-sectional study of 42 solid organ transplant recipients, the association of human cytomegalovirus (HCMV) replication and age with the phenotype of the HCMV-specific CD8+ T cells was analyzed by using the CMV pp65 HLA-A*0201 pentamer. A correlation between the proportion of CD28− HCMV-specific CD8+ T cells and age was observed in patients without HCMV replication (r = 0.50; P = 0.02) but not in patients with HCMV replication (r = −0.05; P = 0.83), a finding which differs from that observed for total CD8+ T cells. Within the group of patients younger than 50 years of age, patients with HCVM replication after transplantation had higher percentages of CD28− HCMV-specific CD8+ T cells (85.6 compared with 58.7% for patients without HCMV replication; P = 0.004) and CD27− HCMV-specific CD8+ T cells (90.7 compared with 68.8% for patients without HCMV replication; P = 0.03). However, in patients older than age 50 years, a high frequency of these two subpopulations was observed in patients both with and without previous HCMV replication (for CD28− HCMV-specific CD8+ T cells, 84.4 and 80.9%, respectively [P = 0.39]; for CD27− HCMV-specific CD8+ T cells 86.6 and 81.5%, respectively [P = 0.16]). In conclusion, the present study shows that in the group of recipients younger than age 50 years, HCMV replication after transplantation is associated with a high percentage of CD27− and CD28− HCMV-specific CD8+ T cells. These results suggest that the increased percentage of CD27− or CD28− HCMV-specific subsets can be considered a biomarker of HCMV replication in solid organ transplant recipients younger than age 50 years but not in older patients. Further studies are necessary to define the significance of these changes in HCMV-associated clinical complications posttransplantation.