Prediction of JENU-Negative Phenotype by Genotyping among Thai Patients with Multiple Transfusions.

Background: The MNS7 (Mi^a) is a low-prevalence antigen associated with GP.Mur hybrid glycophorin, which is high in Thai populations. Consequently, anti-Mi^a, particularly anti-Mur caused by alloimmunisation is involved in transfusion medicine. In Thailand, before the first transfusion of transfusion-dependent patients with thalassemia, typing of Mi^a and Rh antigens is minimally required to provide phenotype-matched donors. A patient with Mi^a-positive phenotype encoded by GYP*Mur homozygote (do not express GPB, JENU-negative) receiving either Mi^a-negative or Mi^a-positive phenotype can produce anti-JENU, leading to difficulty in locating compatible donors. Genotyping for GYP*(B-A-B) hybrid alleles to predict the JENU-negative phenotype is alternatively implemented. This study aimed to predict the JENU-negative phenotype in multitransfused Thai patients using PCR-based coupled DNA sequencing.

Methods: Blood samples from 861 multitransfused Thai patients were included. Mi^a antigen testing was performed using serology and PCR-sequence-specific primer. GYP*(B-A-B) hybrid alleles were analyzed using Sanger DNA sequencing. Only 5 of 68 patients receiving more than 40 red cell units developed alloantibodies. The sequence analysis revealed that 60 of 68 patients carried the GYP*Mur allele, including GYP*Mur/GYPB heterozygotes (86.76%) and the GYP*Mur/GYP*Mur homozygote (1.47%). The remaining 8 patients were GYP*Thai/GYPB heterozygotes (10.29%) and GYP*Thai II/GYPB heterozygotes (1.47%). The GYP*Bun, GYP*HF, GYP*Hop and GYP*Kip alleles were not observed. One female patient with JENU-negative phenotype received 24 red cell transfusions within 1 year without alloantibody production, which might be due to the number of red blood cell (RBC) units or her disease status.

Conclusions: Concerning this study, multiple transfusions can induce alloantibody production. Therefore, phenotype-match transfusions are beneficial among patients with long-term transfusion therapy, and further investigation of the JENU-negative phenotype is suggested.