Exome sequencing, histoincompatibility and long-term kidney allograft function

BACKGROUND: Kidney transplantation is the treatment of choice for most patients with end-stage renal disease and existing data suggest that post transplant graft function is a predictor of kidney graft failure. METHODS: Exome sequencing of DNA from kidney graft recipients and their donors was used to determine recipient and donor mismatches at the amino acid level. The number of mismatches that are more likely to induce an immune response in the recipient was computationally estimated and designated the allogenomics mismatch score. The relationship between the allogenomics score and post transplant kidney allograft function was examined using linear regression. RESULTS: A significant inverse correlation between the allogenomics mismatch score and kidney graft function at 36 months post transplantation was observed in a discovery cohort of kidney recipient-donor pairs (r²>=0.57, P<0.05, the score vs. level of serum creatinine or estimated glomerular filtration rate). This relationship was confirmed in an independent validation cohort of kidney recipient-donor pairs. We observed that the strength of the correlation increased with time post-transplantation. This inverse correlation remained after excluding HLA loci from the calculation of the score. Exome sequencing yielded allogenomics scores with stronger correlations with graft function than simulations of genotyping assays which measure common polymorphisms only. CONCLUSIONS: The allogenomics mismatch score, derived by exome sequencing of recipient-donor pairs, facilitates quantification of histoincompatibility between the organ donor and recipient impacting long-term post transplant graft function. The allogenomics mismatch score, by serving as a prognostic biomarker, may help identify patients at risk for graft failure.