Molecular Screening for Vel- Blood Donors in Southwestern Germany.

BACKGROUND The SMIM1 protein carries the Vel blood group antigen, and homozygosity for a 17 bp deletion in the coding region of the SMIM1 gene represents the molecular basis of the Vel- blood group phenotype. We developed PCR-based methods for typing the SMIM1 17 bp (64-80del) gene deletion and performed a molecular screening for the Vel- blood type in German blood donors. METHODS For SMIM1 genotyping, TaqMan-PCR and PCR-SSP methods were developed and validated using reference samples. Both methods were used for screening of donors with blood group O from southwestern Germany. Heterozygotes and homozygotes for the SMIM1 64-80del allele were serologically typed for the Vel blood group antigen. In addition, the rs1175550 SNP in SMIM1 was typed and correlated to the results of the phenotyping. RESULTS Both genotyping methods, TaqMan-PCR and PCR-SSP, represent reliable methods for the detection of the SMIM1 64-80del allele. Screening of 10,598 blood group O donors revealed 5 individuals homozygous for the deletional allele. They were confirmed Vel- by serological typing. Heterozygotes for the 64-80del allele showed different antigen expressions ranging from very weak to regular positive. CONCLUSION Molecular screening of blood donors for the Vel- blood type is feasible and avoids the limitations of serological typing which might show false-negative results with heterozygous individuals. The identification of Vel- blood donors significantly contributes to the adequate blood supply of patients with anti-Vel.