Similarity of Gut Microbiota Composition between Donor and Recipient May Predict Graft Function after Transplant

Graft outcomes of unrelated-donor kidney transplant have been known to be comparable with those of related-donor kidney transplant despite their genetic distance. We aimed to identify whether the similarity of donor–recipient microbial community may affect early transplant outcomes. We collected stool samples from 67 pairs of kidney transplant recipients and donors and metagenomic 16s DNAs were extracted and analyzed. Differences in gut microbiome between donors and recipients were determined using weighted UniFrac distance.In donor–recipient pairs, 30 (44.8%) pairs were related and 37 (47.8%) pairs were unrelated. The unrelated pairs, especially spousal pairs had closer microbial distances, and they more frequently shared their meals than related pairs did. The microbial distance showed an inverse correlation with the 6-month allograft eGFR (p = 0.034), and correlation was particularly significant in the unrelated pairs (p = 0.003). Only in unrelated pairs, the microbial distance showed an excellent accuracy to predict the eGFR of <60 mL/min/1.73 m2 at 6 months post-transplantation, and it was better than HLA and ABO incompatibilities. Furthermore, the incidence of infection within 6 months post-transplantation increased in the far-distance group when compared with the other groups.Unrelated transplant pairs had closer microbial distance than genetically related pairs. Furthermore, microbial similarity in unrelated donors and recipients might affect allograft function until 6 months after kidney transplantation.