Purpose Post-transplant CMV reactivation from latently-infected lung allografts is extremely prevalent and results in inferior long-term outcomes. CMV latently infected cells ubiquitously express a viral surface protein, US28. We aimed to evaluate the therapeutic effects of a novel immunotoxin (F49A-FTP) that targets US28 in human lungs during EVLP, with the ultimate goal of minimizing or preventing CMV transmission and reactivation post-transplantation. Methods Human lungs rejected for transplantation were randomly placed on EVLP alone or EVLP+1mg/L of F49A-FTP (n=6 each) for 6 hours. Biopsies were collected pre and post EVLP and subjected to an in vitro assay designed to evaluate viral reactivation capacity (Fig 1A). Based on US28's homology to the human CX3CR1 chemokine receptor, potential off-target effects of the toxin were studied evaluating cell death markers of CD34+ and CD14+ using flow cytometry, and the ratio of cells post:pre perfusion were calculated. Lung function on EVLP and inflammatory cytokine production were evaluated as safety endpoints. Results Delivery of F49A-FTP during EVLP showed no acute toxic events demonstrated by no significant differences in lung physiology and levels of IL-8, IL1-b and IFN-γ between the groups. Furthermore, while control lung tissue demonstrated a median increase from baseline of 32% (Range -16% to +112.5%) in viral reactivation, treated lungs demonstrated a significant median reduction in CMV reactivation of 76% (Range -15% to -99.9%) (Fig 1B, p=0.0087). No off-target effects were noted upon F49A-FTP delivery, demonstrated by similar amounts of cell death between the groups (Fig 1C). Conclusion We demonstrate that ex vivo F49A-FTP treatment of human lungs on EVLP markedly attenuates CMV reactivation and could potentially be used to treat donor organs prior to transplant. Ongoing in vivo reactivation experiments using the EVLP treated samples in a humanized mouse will further validate these findings.

Ex vivo enzymatic treatment can efficiently remove blood type antigen in donor lungs without acute side effects. This treatment has potential to be developed as an adjuvant therapy in ABO-incompatible organ transplantation, minimizing the need for recipient antibody removal procedures or augmented immunosuppression.