#1621 Initial results after the implementation of an immunoguided cytomegalovirus prevention protocol in kidney transplant recipients

Abstract Background and Aims The assessment of cellular immunity against cytomegalovirus (CMV) is a valuable tool for tailoring infection prevention strategies in the context of kidney transplantation. This approach enables the individualization of antiviral therapy, aiming to balance the risk of infection with the toxicity associated with treatments. As such, various clinical practice guidelines recommend implementing CMV prevention protocols based on immunosurveillance techniques. The aim of this study is to evaluate the outcomes of a new immunosurveillance-based CMV infection prevention protocol initiated at our center. Method This is a retrospective, descriptive study analyzing the initial outcomes following the implementation of a CMV prevention protocol based on immunosurveillance using the QuantiFERON®-CMV (QF-CMV) assay. A total of 47 consecutive kidney transplant recipients at our center between February and June 2024 were evaluated, with a minimum post-transplant follow-up of 6 months. The protocol is summarized in Fig. 1. Results Of the 47 patients, 9 were CMV seronegative and did not undergo QF-CMV testing for prevention strategy adjustment, thus being excluded from this analysis. In the remaining 38 CMV-seropositive patients, the prevention strategy was adjusted based on QF-CMV results starting at the first post-transplant month, as outlined in the referenced protocol. Among the seropositive patients, 21 (55%) received induction therapy with basiliximab, while 17 (45%) received thymoglobulin. QF-CMV testing was positive in 16 patients (42%) at the first month, in 20 patients (52%) at the second month, and in 26 patients (68%) at the third month. All patients with a positive QF-CMV test transitioned from antiviral prophylaxis to a preemptive therapy approach after the positive result. From the third month onward, preemptive therapy was also initiated in patients with negative or indeterminate QF-CMV results who had received basiliximab induction. Consequently, after the third month, only 5 patients who had received thymoglobulin induction and whose QF-CMV results remained negative/indeterminate continued antiviral prophylaxis. Six cases of CMV reactivation (defined as viral load >500 copies/mL) were identified, all occurring during preemptive therapy. The QF-CMV test prior to viral detection was negative in 3 cases and positive in 3 cases, but the quantitative interferon levels were below 1 IU/ml in all instances. In the seropositive cohort, 3 cases of BK virus infection were detected, with prior QF-CMV results being negative/indeterminate before viremia onset. Conclusion • The use of QF-CMV enables individualized CMV prevention strategies in transplant recipients, reducing exposure to antiviral therapies without increasing the risk of infection. • Further experience with this technique is needed to refine protocols and to consider adjustments to the test's cutoff point to enhance its performance.