ELISPOT assays with pp65 peptides or whole HCMV antigen are reliable predictors of immune control of HCMV infection in seropositive kidney transplant recipients

Human cytomegalovirus (HCMV) infection represents a major complication for solid organ transplant recipients. The aim of this study was to verify if the measurement of HCMV‐specific T‐cells could help to identify patients protected against HCMV disease cytokine flow cytometry using infected dendritic cells as stimulus (CFC‐iDC, which discriminates between CD4(+) and CD8(+) T cells), and ELISPOT, using infected cell lysate (ELISPOT‐iCL) or pp65 (ELISPOT‐pp65) as stimulus, were adopted. Among the 47 kidney transplant recipients (KTR) enrolled, 29 had a self‐resolving HCMV infection (Controllers) and 18 required antiviral treatment (Non‐Controllers). HCMV‐specific T‐cell frequency at the peak of HCMV infection identified Controllers and Non‐Controllers, although the diagnostic performance of CD8(+) CFC‐iDC (area under the curve [AUC] of the receiver‐operator characteristic curve: 0.65) was lower than that of CD4(+) CFC‐iDC (AUC: 0.83), ELISPOT‐iCL (AUC: 0.83) and ELISPOT‐pp65 (AUC: 0.80). CFC‐iDC detected a protective immune reconstitution significantly earlier (median time: 38 days) than ELISPOT‐iCL and ELISPOT‐pp65 (median time: 126 and 133 days, respectively). Time to protective immune reconstitution in Non‐Controllers was significantly longer than in Controllers with the ELISPOT and the CD4(+) CFC‐iDC assays, but not with CD8(+) CFC‐iDC. The majority of patients did not require antiviral treatment after protective immune reconstitution, with the exception of five patients according to CFC‐iDC assay, one patient according to ELISPOT‐iCL assay and three patients according to ELISPOT‐pp65 assay. Monitoring the HCMV‐specific immunological reconstitution with is effective in discriminating KTR at risk of or protected from HCMV disease and the ELISPOT assays are suitable for implementation in the clinical setting.