FEASIBLE EXTENDED HLA TYPING OF DECEASED DONORS IN SOLID ORGAN TRANSPLANTATION

In solid organ transplantation the HLA-A, -B, -DR, -DQ donor-recipient matching results are insufficient for highly sensitized patient. In fact, solid phase single antigen assays, used to define HLA antibodies in transplant candidates, show the presence of antibodies specific for all HLA molecules. Thus, an extended HLA typing of deceased donor is necessary to improve selection of the most suitable transplant candidate. Until July 2016, in our laboratory all donors were typed for HLA-A,-B,-C,-DR,-DQ loci by PCR-SSP technique; when a sensitized patient was selected, the donor typing was prospectively enlarged to pertinent HLA molecules. To simplify this procedure and improves organ allocation we introduced the new RT PCR-SSP technique, based on an innovative chemistry (Linkage Bioscience Inc.), it enables us to provide intermediate resolution typing of 11 HLA loci, in less than 90 minutes. Allele-specific amplification combined with SYBR Green and real-time PCR instruments are used to detect amplification products and to collect dissociation data for automatic interpretation by SureTyper software. Since August 2016, 76 potential deceased donors were typed by this technique. No allelic ambiguities were evidenced but rather high resolution typing were obtained in several cases: 11 HLA-A alleles, 55 HLA-B alleles, 48 HLA-C alleles, 41 HLA-DRB1 alleles, 37 HLA-DRB345 alleles, 20 HLA-DQA1 alleles, 30 HLA-DQB1 alleles, one HLA-DPA1 allele, and 50 HLA-DPB1 alleles. Moreover, the extended HLA typing obtained by RT PCR-SSP avoided additional HLA-C,-DRB1, -DQA1 and-DPB1 typing in 12 cases (15,8%) and allowed to define donor molecules against which 10 patients (13,2%) showed preformed high fluorescence intensity antibodies (MFI >5000). In conclusion, RT PCR-SSP is less hands-on and, considering the number of typed HLA loci, cheaper than traditional PCR-SSP techniques. The extended donor HLA typing gives useful information for a more precise pre-transplant virtual crossmatch and for a better donor-recipient selection to improve clinical transplant outcome.