Background: Pre-tx donor-specific antibodies (DSA) raises the risk for antibody-mediated rejection (ABMR) and graft dysfunction. The role of AT1R Ab is unclear. In adults, post-tx AT1R Ab can lead to malignant HTN, ABMR, graft thrombosis and failure. We previously showed ped pts with post-tx AT1R Ab and DSA developed ABMR +/- acute cellular rejection and pts with isolated post-tx AT1R Ab did not. Here we examined pre-tx AT1R Ab levels in ped KTx pts, compared their estimated GFR (eGFR) at 1-year (yr), 2-yr, at most recent follow-up (f/u), and evaluated the incidence of HTN and ABMR.

Methods: 15 non-sensitized (PRA <30 and negative crossmatch) ped KTx pts, 2-17 yrs old, with pre-tx AT1R Ab testing by ELISA were included. Pts were divided into two groups (Grp): Grp A did not have strong pre-tx AT1R Ab (≤16 units/mL) and Grp B had strong pre-tx AT1R Ab (≥17 units/mL). Pts received induction immunosuppression with anti-thymocyte globulin or anti IL-2R and maintained on mycophenolate mofetil, tacrolimus, and +/- steroids. Post-tx eGFR at 1-yr, 2-yr, and at most recent f/u were determined by the Schwartz equation. Presence of HTN needing anti-HTN medication(s) was also evaluated. Kidney biopsy (KBx) was done in the setting of strong DSA (MFI >10,000) or elevated creatinine and scored by Banff criteria.

Results: Of 15 pts, 7 were in Grp A and 8 were in Grp B. At 1-yr f/u, median eGFR was 113.5 ml/min/1.73m² (range 96.4-149.1) in Grp A and 108.6 (range 86.3-162.4) in Grp B (p=0.96). At 2-yr f/u, median eGFR was 115.7 (range 98.2-123.3) in Grp A and 107.2 (range 96.1-139.7) in Grp B (p=0.78). Median time of most recent f/u is 52.8 months post-tx (range 22.9-78.9); median eGFR was 94.6 (range 82.1-125.6) in Grp A and 102.4 (range 75-158.0) in Grp B (p=0.90). HTN was noted in 4 of 7 (57%) pts in Grp A and in 2 of 8 (25%) pts in Grp B (p=0.31). Pts in Grp A did not undergo a KBx. Two of 8 pts in Grp B had a KBx for strong de novo DSA and strong post-tx AT1R Ab: both pts showed ABMR.

Conclusion: In non-sensitized ped KTx recipients, isolated strong pre-tx AT1R Ab is not associated with reduced graft function at 1-yr, 2-yr, up to 6-yr post-tx and does not increase the risk for developing HTN. However, the presence of post-tx strong DSA plus strong AT1R Ab is associated with ABMR.

CITATION INFORMATION: Pizzo H., Choi J., Haas M., Zhang X., Kamil E., Kim I., Jordan S., Puliyanda D. Isolated Pre-Transplant Angiotensin II Type I Receptor Antibodies (AT1R Ab) Are Not Associated with Reduced Graft Function or Hypertension (HTN) in Pediatric Kidney Transplant (Ped KTx) Patients (pts) Am J Transplant. 2017;17 (suppl 3).

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