Comparison of the Commercial QuantiFERON-CMV and Overlapping Peptide-based ELISPOT Assays for Predicting CMV Infection in Kidney Transplant Recipients

Abstract

Cytomegalovirus (CMV) is one of the most important opportunistic infections in transplant recipients. Tests for CMV-specific T cell responses have been proposed to change the current risk stratification strategy using CMV assays. We evaluated the usefulness of pre-transplant CMV-specific T cell assays in kidney transplant (KT) candidates for predicting the development of CMV infection after transplantation comparing the results of the overlapping peptides (OLPs)-based enzyme-linked immunospot (ELISPOT) assay and the commercial QuantiFERON-CMV assay. We prospectively enrolled all cases of KT over a 5-month period, except donor CMV-seropositive and recipient seronegative transplants that are at highest risk of CMV infection. All the patients underwent QuantiFERON-CMV, CMV OLPs-based pp65, and immediate-early 1 (IE-1)-specific ELISPOT assays before transplantation. The primary outcome was the incidence of CMV infection at 6 months after transplant. The total of 47 KT recipients consisted of 45 living-donor KTs and 2 deceased-donor KTs. There was no association between positive QuantiFERON-CMV results and CMV infection. However, 10 of 34 patients with phosphoprotein 65 (pp65)- or IE-1-specific ELISPOT results higher than cut-off value developed CMV infections compared with none of 13 patients with results lower than cut-off value developed CMV. The OLPs-based ELISPOT assays are more useful than the QuantiFERON-CMV assay for predicting CMV infection. Patients with higher CMV-specific T cell immunity at baseline appear to be more likely to develop CMV infections after KT, suggesting that the abrupt decline in CMV-specific T cell responses after immunosuppression, or high CMV-specific T cell responses due to frequent CMV activation before KT, may promote CMV infection.

Keywords: Cell-mediated Immunity; Cytomegalovirus; Enzyme-linked immunospot assay; Interferon-gamma Release Test.

Figure 1

Flow chart of the study. The chart indicates the number and percentage of patients with CMV episode within the group of patients with positive or negative results of assay that defined by the cut-off value obtained from ROC curve. CMV, cytomegalovirus; ROC, receiver operating characteristic; LDKT, living-donor kidney transplant; DDKT, deceased-donor kidney transplant; pp65, phosphoprotein 65; IE-1, immediate-early 1; ELISPOT, enzyme-linked immunospot.

Figure 2

Pre-transplant CMV-specific T cell responses in the patients with CMV episode. CMV-specific T cell responses were measured by stimulating PBMCs with OLPs pools of (A) pp65, (B) IE-1 in ELISPOT or (D) combination of immunodominant peptides of CMV in QuantiFERON-CMV. The combined result of (A) and (B) is represented in (C) pp65 or IE-1. In (A-C), pre-transplant CMV-specific T cell responses of the patients with post-transplant CMV episode were likely to be higher than the patients without post-transplant CMV episode. In (D), however, IFN-γ concentration was tended to lower in the patients with CMV infection. Each result was obtained by 2 repeated experiments. CMV, cytomegalovirus; PBMC, peripheral blood mononuclear cell; OLP, overlapping peptide; pp65, phosphoprotein 65; IE-1, immediate-early 1; ELISPOT, enzyme-linked immunospot; IFN, interferon.