LAUSR

Background Solid organ transplant recipients (SOTRs) are predisposed to infection due to the need for lifelong immunosuppression, although tools to measure the overall degree of immunosuppression are limited. In this study, we used a novel global cell-mediated immunity (CMI) assay to quantify the degree of immunosuppression and predict subsequent infections. Methods Consecutive SOTRs were enrolled and provided whole blood to conduct the global CMI assay (QuantiFERON Monitor) at 1, 3, and 6 months posttransplant. The assay measures plasma interferon gamma (IFN-γ) levels after stimulation of whole blood with antigens that stimulate both innate and adaptive immunity. Bacterial, viral, and fungal infections were prospectively recorded. Results We enrolled 137 patients who provided CMI measurements on at least 1 study timepoint. Median age was 58 years; transplant types were kidney (32.1%), liver (30.7%), and lung (36.5%). At least 1 episode of infection occurred in 32 of 137 (23.4%) patients between 1 and 3 months, 34 of 135 (25.1%) between 3 and 6 months, and 39 of 132 (29.5%) between 6 and 12 months. IFN-γ levels were significantly lower in those with at least 1 episode of infection vs no infection at month 1 (P = .04), month 3 (P = .05), and month 6 (P = .006). Patients who developed opportunistic infections (OIs) also showed a significantly lower CMI than those without OI at months 3 and 6. Using a cutoff value of ≤10 IU/mL of IFN-γ, there was a 2- to 3-fold greater likelihood of subsequent infection in those with lower CMI. Conclusions We show that a novel global immunity assay is able to quantify the level of immunosuppression and predict the risk of subsequent infection episodes in organ transplant recipients.