Quantiferon®-Monitor: A Potential Biomarker of Immunosuppression in Lung Transplantation

Purpose Determining the optimal level of immunosuppression in lung transplant (LT) recipients is challenging. The Quantiferon®-Monitor (QFM) is a novel immune function assay that measures interferon-γ after stimulation with ligands for the innate & adaptive immune system. The aim of this prospective cohort study was to assess the relationships between immunosuppression and QFM results, and the clinical utility of QFM as a predictor of infection/rejection in LT. Methods QFM was tested pre & at 2, 6, 12, 24 & 52 weeks post-LT. Standard immunosuppression included tacrolimus, azathioprine, prednisone & basiliximab in patients with limited renal reserve. Patients were assessed over 1yr for rejection & infection. Results 80 LT patients were recruited from 2015-17 (median age 61, 60% male, 86% bilateral LT and 50% received basiliximab). Pre-transplant QFM results were lower in patients receiving glucocorticoids (median 67 IU/mL, IQR 9-244 vs. 314, 67-499, p=0.01) and those testing cytomegalovirus (CMV) seronegative (71, 5-262 vs. 230, 58-499, p=0.01). QFM values decreased significantly post-transplant then progressively increased (Figure). Trough tacrolimus levels & prednisone doses were associated with post-transplant QFM levels (p 1000 copies/mL in 15%), respiratory viral infections in 40% & positive BAL bacterial cultures in 64%. 9 patients (11%) experienced rejection, 4 within 30 days post-transplant. 76% were readmitted & 5 died within 1 yr. QFM results at 2 & 6 weeks were not associated with any of these outcomes. Conclusion Our study demonstrated an association between tacrolimus levels, prednisolone dose & QFM results but was underpowered to detect differences in clinical outcomes. CMV serostatus appeared to have an impact on QFM results both pre- & post-transplant.