Plasma Proteomic biomarkers provide mechanistic insights into CAN/IFTA in kidney recipients

John Friedewald¹, Daniel Salomon², Peter Langfelder³, Stephen Horvath³, Ed Wang¹, Sunil Kurian², Tony Mondala², Karri Ballard⁴, Ralph McDade⁴, Michael Abecassis¹.

¹Comprehensive Transplant Center, Northwestern University, Chicago, IL; ²The Scripps Research Institute, Department of Molecular and Experimental Medicine, La Jolla, CA; ³UCLA Biostatistics, Los Angeles, CA; ⁴Rules-Based Medicine, Austin, TX, USA.

Renal dysfunction (RD) has multiple causes in renal transplant (RT) recipients including various cellular and molecular mechanisms of injury. There is a pressing need for biomarkers that can predict and follow the course of RD in RT recipients. We have utilized two novel plasma Luminex-based, multi-analyte proteomic (kidney injury and discovery) panels. First, we compared RT recipients with and without acute rejection (AR) (n=25/group). Second, we compared RT recipients with and without CAN/IFTA (n=25/group). Third, we compared liver transplant (LT) recipients with and without chronic kidney disease (CKD) (n=33 and 31, respectively).

Thirty-nine proteins were differentially detected in subjects with AR (predictive accuracy 78%, sensitivity 76%, specificity 80%, PPV 79%). Sixty protein analytes were differentially detected in subjects with CAN/IFTA (predictive accuracy 92%, sensitivity 96%, specificity 88%, PPV of 89%). The 18 highest ranked candidates for CAN/IFTA biomarkers included: IL10, IL13, VCAM1, VEGF, TRAILR3, TNFR2, FAS and MMP3, most of which have been linked mechanistically to CAN/IFTA in transplant models and several overlap with proteins also found in AR patients. These results underscore the importance of dysregulated alloimmunity in the pathogenesis of CAN/IFTA. Finally, 10 different proteins (related to tissue injury and repair, not alloimmunity) were differentially expressed in LT recipients with CKD. All findings were statistically significant.

Our data show that several known kidney non-immune injury biomarkers are significantly elevated in all 3 settings. However, our novel discovery panel shows significant elevations in immune/inflammation biomarkers for both AR and CAN/IFTA in RT recipients, but not for CKD in LT recipients. These results suggest that the cellular and molecular basis of CAN/IFTA is alloimmune/inflammatory and thus, reflects a gap in effective immunosuppression. These biomarkers may help assess the adequacy of long-term immunosuppression, inform the value of new drug trials and offer mechanistic insights. Further validation is now underway.