P135 New frequent HLA-DPB1/DPA1 haplotypes in low resolution typing

Aim The linkage between DPB1 and DPA1 was extensively studied in 5,944 European American stem cell donors (Hollenbach et al., 2012). Thirty-three DPB1 alleles and associated DPA1 were reported. In 2014, Voorter et al. reported the special association of DPB1∗105:01 with DPA1∗03:01 in contrast to DPB1∗04:02-DPA1∗01:03 association although both DPB1∗105:01 and DPB1∗04:02 belong to the same G group. Here we retrospectively reviewed 1938 renal recipients with DP typing and report new DPB1/DPA1 associations frequently seen in our cohort. Methods HLA-DPB1 and DPA1 typing was performed by rSSO (One Lambda, Thermo-Fisher). Haplotypes were inferred by Clark’s method published in 1990. Results We identified 11 DPB1 alleles whose association with DPA1 has never been reported previously (Table 1). Five DPB1 alleles, DPB1∗124:01, 126:01, 131:01, 350:01 and 352:01, are not in the 2013 CWD list. Of note, DPB1∗131:01 was detected at high frequency (2.9%) in our cohort. The association of these five DPB1s with DPA1 was the same as the most frequent allele in the same G group, e.g. DPB1∗126:01 and DPB1∗350:01 are both associated with DPA1∗01:03 the same as DPB1∗04:01. Six DPB1 CWD alleles observed in our cohort were not reported in Hollenbach’s study. In 2015, Aaron et al. reported significant variation of DPB1 frequency in four major ethnic groups. In their study, DPB1∗29:01, 39:01, 40:01, and 85:01 were much more frequent in African American than other three ethnic groups. High percentage of African American in our renal recipients (44%) may explain the detection of these alleles in our cohort. Interestingly DPB1∗106:01 was associated with DPA1∗02:01, unlike PB1∗19:01 which is in the same G group however is associated with DPA1∗02:02. Conclusions We reported 11 new DPB1/DPA1 haplotypes frequently seen in DP low resolution typing. Five non-CWD DPB1 alleles were identified frequently. The enrichment of some alleles in our cohort could be attributed to high incidence of African American in our patients. Download : Download high-res image (190KB) Download : Download full-size image