CD154-expressing CMV-specific T cells associate with freedom from DNAemia and may be protective in seronegative recipients after liver or intestine transplantation.

Cell-mediated immunity to CMV, if known, could improve antiviral drug therapy in at-risk children and young adults with LT and IT. Host immunity has been measured with CMV-specific T cells, which express IFNγ, but not those which express CD154, a possible substitute for IFNγ. CMV-specific CD154+ T cells and their subsets were measured with flow cytometry after stimulating PBL from recipient blood samples with an overlapping peptide mix of CMV-pp65 antigen for up to 6 hours. CMV-specific CD154+ T cells co-expressed IFNγ in PBL from three healthy adults and averaged 3.8% (95% CI 3.2%-4.4%) in 40 healthy adults. CMV-specific T cells were significantly lower in 19 CMV DNAemic LT or IT recipients, compared with 126 non-DNAemic recipients, 1.3% (95% CI 0.8-1.7) vs 4.1 (95% CI 3.6-4.6, P < .001). All T-cell subsets demonstrated similar between-group differences. In logistic regression analysis of 46 training set samples, 12 with DNAemia, all obtained between days 0 and 60 from transplant, CMV-specific T-cell frequencies ≥1.7% predicted freedom from DNAemia with NPV of 93%. Sensitivity, specificity, and PPV were 83%, 74%, and 53%, respectively. Test performance was replicated in 99 validation samples. In 32 of 46 training set samples, all from seronegative recipients, one of 19 recipients with CMV-specific T-cell frequencies ≥1.7% experienced DNAemia, compared with 8 of 13 recipients with frequencies <1.7% (P = .001). CMV-specific CD154+ T cells are associated with freedom from DNAemia after LT and IT. Among seronegative recipients, CMV-specific T cells may protect against the development of CMV DNAemia.

Predicting Cellular Rejection With a Cell-Based Assay: Preclinical Evaluation in Children.

BACKGROUND: Allospecific CD154+T-cytotoxic memory cells (CD154+TcM) predict acute cellular rejection after liver transplantation (LTx) or intestine transplantation (ITx) in small cohorts of children and can enhance immunosuppression management, but await validation and clinical implementation. METHODS: To establish safety and probable benefit, CD154+TcM were measured in cryopreserved samples from 214 children younger than 21 years (National Clinical Trial 1163578). Training set samples (n = 158) were tested with research-grade reagents and 122 independent validation set samples were tested with current good manufacturing practices-manufactured reagents after assay standardization and reproducibility testing. Recipient CD154+TcM induced by stimulation with donor cells were expressed as a fraction of those induced by HLA nonidentical cells in parallel cultures. The resulting immunoreactivity index (IR) if greater than 1 implies increased rejection-risk. RESULTS: Training and validation set subjects were demographically similar. Mean coefficient of test variation was less than 10% under several conditions. Logistic regression incorporating several confounding variables identified separate pretransplant and posttransplant IR thresholds for prediction of rejection in the respective training set samples. An IR of 1.1 or greater in posttransplant training samples and IR of 1.23 or greater in pretransplant training samples predicted LTx or ITx rejection in corresponding validation set samples in the 60-day postsampling period with sensitivity, specificity, positive, and negative predictive values of 84%, 80%, 64%, and 92%, respectively (area under the receiver operator characteristic curve, 0.792), and 57%, 89%, 78%, and 74%, respectively (area under the receiver operator characteristic curve, 0.848). No adverse events were encountered due to phlebotomy. CONCLUSIONS: Allospecific CD154+T-cytotoxic memory cells predict acute cellular rejection after LTx or ITx in children. Adjunctive use can enhance clinical outcomes.