TNF-α Production by Monocytes Stimulated With Epstein-Barr Virus–Peptides as a Marker of Immunosuppression-Related Adverse Events in Kidney Transplant Recipients

INTRODUCTION: Infections and cancers now outnumber rejection as a cause of morbidity in transplant recipients, likely as a result of over-immunosuppression. Currently, there is no clinical tool to detect over-immunosuppression. We recently reported that tumor necrosis factor alpha (TNF-α) production by CD14(+)CD16(+) intermediate monocytes, following ex vivo stimulation by Epstein-Barr virus–peptides, could identify over-immunosuppressed patients. METHODS: We conducted a pilot study the assay using 142 peripheral blood mononuclear samples from a cohort of 71 kidney transplant recipients. Patients were classified as cases or controls according to the occurrence of opportunistic infection, recurring bacterial infections or de novo neoplasia in the 12 months following blood collection. We used both the classifier rule and a threshold of <73% of CD14(+)CD16(+)TNFα(+) cells developed in a previous training set. RESULTS: Cases were detected with 83% sensitivity and 68% specificity. The negative predictive value of the assay was 89%. The hazard ratio for the occurrence of the endpoint was 6.8 (95% confidence interval 2.0–23.9; P = 0.003) in patients with a positive test. Multivariable linear regression analysis revealed that the association was independent of baseline clinical characteristics, renal function, and immunosuppressive regimen. CONCLUSION: These data validate this cell-based assay as a promising tool for personalizing immunotherapy. Studies are under way for a 2-step assay with improved specificity.