Age-dependent association between low frequency of CD27/CD28 expression on pp65 CD8+ T cells and cytomegalovirus replication after transplantation

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.

FIG. 1.

Plots of pentamer-labeled HCMV-specific CD8⁺ T cells from four representative transplant recipients. (A) HCMV D⁺/R⁻ patient and no HCMV replication (n = 3; median, 0.41%; range, 0.30 to 0.60%); (B) HCMV D⁺/R⁻ patient and HCMV replication (n = 6, median%, 1.24; range, 0.12 to 4.15%); (C) HCMV R⁺ patient and no HCMV replication (n = 19, median%, 2.45; range, 0.14 to 22.00%); (D) HCMV R⁺ patient and HCMV replication (n = 14, median, 3.79%; range, 0.14 to 13.20%). Values indicate the percentage of pentamer-positive cells with reference to the total number of CD8 T cells. n, number of patients for each situation; total number of patients, 42.

FIG. 2.

(A) Correlation between age and CD28⁻ total CD8⁺ T-cell percentage in patients with HCMV replication (•; linear regression, solid line) and without HCMV replication (○; linear regression, dashed line). (B) The same analysis described for panel A for CD27⁻ total CD8⁺ T cells. (C and D) Box plots for CD28⁻ and CD27⁻ total CD8⁺ T-cell frequency, respectively, according to age (<50 and >50 years) (open boxes, patients without HCMV replication; shaded boxes, patients with HCMV replication). The median value of each data set is shown as a horizontal line within the box, which encompasses the 25th and 75th percentiles. The whiskers extending from either end of the box represent the range of the data.

FIG. 3.

(A) Correlation between age and CD28⁻ HCMV-specific CD8⁺ T-cell percentage in patients with HCMV replication (•; linear regression, solid line) and without HCMV replication (○; linear regression, dashed line). (B) The same analysis described for panel A for CD27⁻ HCMV-specific CD8⁺ T cells. (C and D) Box plots for CD28⁻ and CD27⁻ HCMV-specific CD8⁺ T-cell frequency, respectively, according to age (<50 and >50 years) (open boxes, patients without HCMV replication; shaded boxes, patients with HCMV replication). HCMV-specific CD8⁺ T-cell data are expressed as the proportion of total CD8⁺ T cells. The median value of each data set is shown as a horizontal line within the box, which encompasses the 25th and 75th percentiles. The whiskers extending from either end of the box represent the range of the data.

FIG. 4.

Scatter plots showing correlations between percentages of CD28⁻ and CD27⁻ HCMV-specific CD8⁺ T cells and the amounts of perforin (A and B) and granzyme B (C and D) produced by these subpopulations. Spearman's rank correlation test was used for statistical analysis; a P value of <0.05 was considered significant.