Impact of age and cytomegalovirus on CD8+ T-cell compartment remodeling after solid organ transplantation: A one-year follow-up study

- Age and CMV-serostatus influence the baseline frequency of CD27− CD28− CD8+ T cells.
- The additional posttransplant expansion is associated with late CMV replication.
- A stable high frequency of these cells might impact on further virus reactivation.

Cytomegalovirus (CMV), a member of the β-herpesvirus family, is a major complicating infection in transplant patients. CMV latency has a long-term impact on CD8+ T-cell differentiation. It is unclear, however, whether this effect can be detected in one-year period. To investigate this, we analyzed the remodeling of the CD8+ T-cell compartment during the first year after solid organ transplantation. A total of 55 kidney or lung transplant patients were recruited. CD8+ T-cell subsets were prospectively analyzed at pretransplant, at 3 or 6 months and 12 months after transplantation (mo post-Tx). A significant increase in the frequency of CD27− CD28− CD8+ T cells (from 32.8% to 42.3%; p = 0.014) was observed from pretransplant to 12 mo post-Tx. Further analysis, however, showed that the largest expansion was observed from 3/6 to 12 mo post-Tx whereas small non-significant variations were observed from pretransplant to 3/6 mo post-Tx. The adjusted analysis showed that age and CMV seropositivity were statistically associated with the baseline frequency of CD27− CD28− CD8+ T cells. Additionally, CMV replication was related to the posttransplant expansion of this subpopulation, since it was not observed in patients without CMV viremia (24% vs. 4.2%). The results indicate that the expanded frequency associated with late CMV replication is additive to the baseline frequency related to aging and CMV seropositivity. If the expanded frequency remains at this high level for a long period it might have clinical consequences related to the control of future reactivations of CMV or of other related viruses.