Symptomatic and asymptomatic viral recrudescence in solid-organ transplant recipients and its relationship with the antigen-specific CD8(+) T-cell response

Abstract

Using ex vivo antigen-specific T-cell analysis, we found that symptomatic cytomegalovirus recrudescence in transplant recipients was coincident with reduced expression of gamma interferon (IFN-gamma) by virus-specific CD8(+) T cells and an up-regulation of CD38 expression on these T cells, although there was no significant change in the absolute number of virus-specific cells (as assessed by major histocompatibility complex-peptide multimers). In contrast, HLA class I-matched transplant patients with asymptomatic viral recrudescence showed increased expansion of antigen-specific T cells and highly stable IFN-gamma expression by epitope-specific T cells. These studies suggest that a strong functional T-cell response plays a crucial role in defining the clinical outcome of acute viral recrudescence.

FIG. 1.

Longitudinal functional analysis of HCMV-specific T cells in HLA class I-matched SOT recipients using IFN-γ ELISPOT assays and peptide epitopes from HCMV antigens (Table 1). Data from an individual recipient are presented in each panel. Data from individuals with no evidence of viral recrudescence are presented in panels A to E, those from individuals with asymptomatic recrudescence are presented in panels F to J, and those from individuals with symptomatic recrudescence are presented in panels K to O. Data presented in panels A to E, K, L, and N are based on SOT patients who received heart and/or lung transplants, while data in panels F to J, M, and O are based on renal transplant recipients. Gray-shaded areas in panels K to O indicate the time period when clinically active HCMV disease was diagnosed and the patient was being treated with antiviral medication (Table 2). Patients B, D, and E received antiviral prophylaxis based on oral ganciclovir. The results are expressed as spot-forming cells (SFC) per 10⁶ CD3⁺/CD8⁺ T cells. Also shown in panels F to O is the HCMV load in peripheral blood of these patients as HCMV copies/10⁶ PBMC. Blood sample collection time points (weeks) for each of the donors are indicated on the x axis.

FIG. 2.

Ex vivo enumeration of HCMV-specific CD8⁺ T cells using MHC-peptide multimers. PBMC from SOT recipients were costained with anti-human CD8 tricolor-labeled antibody and phycoerythrin (PE)-labeled MHC-peptide tetramers/pentamers. The fluorescence intensity was assessed with a FACSCalibur, and data were analyzed using Cellquest software. Representative data plots for three different HCMV epitopes, NLV (HLA A2 restricted), VTE (HLA A1 restricted), and TPR (HLA B7 restricted), are shown in panel A. Panel B shows percentages of MHC-peptide multimer-positive CD8⁺ T cells in samples from individuals with no evidence of viral recrudescence, with asymptomatic recrudescence, and with symptomatic recrudescence. Panel C shows the phenotypic analysis of HCMV-specific T cells in these individuals. HCMV-specific T cells were costained with anti-human CD38 antibody. Data presented in panels B and C are based on all the blood samples collected at different time points as indicated in Fig. 1. P values were calculated using the nonparametric Mann-Whitney test. ns, not significant.