Introduction There remains a need for biomarker in transplantation for monitoring and early identification of rejection episodes (R). We developed a colorimetric assay to detect kynurenine (Kyn) changes in serum and saliva. Kynurenine is the first degradation product downstream the tryptophan metabolism and one of the key players concerning inflammatory response and immune-modulation not only on T-regulatory and NK cells. Furthermore, we developed an aptamer based lateral-flow-test (LFIA) especially in saliva.

Materials and Methods 306 healthy blood donors served as normal controls (blood and saliva). Blood samples were measured retrospectively from 442 renal transplant patients (Gr.1, n=6230 probes) and prospectively from 119 patients (Gr.2, n=803 probes) including 68/32 rejections.

Results Test-recovery rate was 97-99,8%, intra-assay variance 1,53%, inter-assay variance 2,77% (B) and 95,6-97,9%, 2,14% and 3,26% for (S). Values in normal controls were 2,7+0,4 [micro]M for serum and 0,7+0,4[micro]M for saliva. Mean values in patients with rejection (BPAR) were 17,4+8,4 [micro]M in (B) and 4,6+1,6 [micro]M in saliva (S) compared to uneventful patients 4,4+1,5 [micro]M (B) and 1,3+0,6[micro]M (S). The proportion rate was equal between normal controls, uneventful patients after transplantation and rejections (3,8:1). We found a) a significant correlation of Kyn and rejection episodes (BPAR) early in the beginning without a false negative/positive result, b) a predictive information concerning the long-term run (n=138; up to 144 mos) and c) excellent tool for monitoring therapeutic interventions (f.e. change of immunosuppressive therapy). There was a significant difference between steroid-sensitive, steroid-resistant and antibody mediated rejection and infection (CMV). There was no difference concerning age, gender and circadian behavior. The first data of the aptamere test are quick, precise and reproducible. Read out is either qualitative or quantitative (via reader). Data from heart, pancreas, liver and small bowel transplantation showing the same results.

Conclusion This test fulfills the given prerequisites for a biomarker test. The test is safe, reliable, easy and quick to perform and not costly. A first prospective clinical multicenter study for the LFIA is underway. This test is useful for a tailored immunosuppressive therapy and gives patients more safety.

CITATION INFORMATION: Abendroth D, Marzinzig M, Stangl M. Preceeding the Rejection: Clinical Results of a Saliva Test After Renal Transplantation. Am J Transplant. 2017;17 (suppl 3).

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