P020 Identification of a new C*06 null allele by SBT typing in an arabic family

A 12 y/o female from Saudi Arabia with chronic granulomatous disease was evaluated at Duke for HSCT. Patient and sibling typing were performed by SBT method (Protrans, Germany) which separates alleles by group-specific PCR before sequencing. The patient was identical to her sibling at HLA-A, B, DRB1, DRB3/4/5 and DQB1 loci. However, the analysis software could not assign alleles at HLA-C locus for both the patient and sibling due to the presence of double peaks in exon 3 electropherogram. For both the patient and the sibling, exon 2 and exon 4 sequences showed no polymorphism. Sequence with forward primer of exon 3 was good 1–224 nt in exon 3 but became double peaks after 224. Reverse primer sequence of exon 3, however, had double peaks 1–224 nt then good after 224. Analyzing the results by ignoring the double peak sequences showed a perfect match to C*06:02 in the database. This indicated there were C*06:02 and another variant of C*06:02 with a G deletion at 224 of exon 3. This corresponds to nt 568 in cDNA which changes codon 166 from GAG to.AG and is predicted to be a null allele due to shift of open reading frame. In order to investigate whether the new variant was inherited from the family, we also obtained the samples from the parents. It turned out the C*06 new null allele was carried by the father. The sequence was submitted to GenBank (accession number MH031344). The patient’s sibling was identified to be the 10/10 matched donor and HSCT was performed in 2018 successfully.