FIG 1.
The magnitude of IFN-γ-secreting CD4+ T cell responses to 6 HCMV proteins is maintained with increasing donor age. (A) The frequency of the CD4+ T cell responses to 11 HCMV protein peptide pools in 18 donors was determined by an IFN-γ ELISPOT assay. The number of donors with a positive response (<100 sfu/million cells after correction for the background count) to each protein is tallied and ranked. The IFN-γ-secreting CD4+ T cell response to 6 HCMV proteins (pp65, gB, IE2, pp71, US3, and IE1) in a cohort of 84 HCMV-seropositive and 13-seronegative donors was measured using an IFN-γ FluoroSpot technique. (B) The results were converted to the number of sfu per million T cells, from which the background counts were subtracted, and the response to each protein and the positive control by the entire cohort is summarized for both CMV-seropositive donors (CMV +ve) and CMV-seronegative donors (CMV −ve). The distribution of the CMV-seronegative donors' responses to each HCMV protein peptide pool and the response to the positive control was used to determine the cutoff for a positive response to the HCMV peptide pool, which was 100 sfu/million cells (dashed line). The proportion of donors responding to each protein and the positive control at a level above the threshold is shown. (C) The proportion of the 84 seropositive donors producing a positive response to 1 or more of the 6 HCMV protein peptide pools is summarized. (D to J) Within the seropositive cohort, the correlation of donor age with the size of the total IFN-γ donor response to all six proteins (D) and the donor response to each protein, pp65 (E), IE1 (F), gB (G), IE2 (H), pp71 (I), and US3 (J), is shown. The correlation of the CMV protein response with age was analyzed using the Spearman rank correlation (Spearman rs values, 95% confidence intervals [in parentheses], and P values are indicated on each graph); a line of best fit (solid) and the 95% confidence intervals (dotted lines) are also shown. Due to the repeated analyses performed, results were considered significant only if P was ≤0.01. ns, not significant.