Brief communication I. Gimferrer HLA-B*5130, a new HLA-B allele carrying a M.T. Arias rare nucleotide substitution in exon 4 V. Fabregat J. Martorell J. Vives F. Lozano Key words: B51; B*5130; B*51011; B*7301; HLA-B; SBT Acknowledgments The authors are deeply indebted to Carlos Vilches and Rosario de Pablo for generously sharing DNA samples and results, and for the critical comments on this manuscript. Received 13 August 2002, revised 20 September 2002, accepted for publication 24 September 2002 Copyright c Blackwell Munksgaard 2003 Tissue Antigens . 0001-2815 Tissue Antigens 2003 61: 97–98 Printed in Denmark . All rights reserved 97 Abstract: We report herein the identification of a new HLA-B*51 allele in a Spanish Caucasoid organ donor. The novel allele, designated B*5130, dif- fers from B*51011 by one nucleotide change at position 787 (A to G) in exon 4, leading to an amino acid change from Arg (AGA) to Gly (GGA) at codon 239 in the a3 domain. This substitution is present in most classical and nonclassical HLA class I loci (A, C, E, and G) but not in any of the HLA- B alleles reported so far, except for B*7301. Although the frequency of the new variant seems to be low, its existence makes mandatory the analysis of exon 4 before assigning a B*5101 type. HLA-B51 is a relatively frequent specificity among the Caucasoid and Oriental ethnic groups, being the dominant allotype carrying the Bw4 epitope among South American Indian populations (1). HLA-B51 is strongly associated with Behcet’s disease in many dif- ferent ethnic groups (2,3). To date, 29 HLA-B*51 alleles (B*5101- B*5129) have been identified (http://www.ebi.ac.uk/imgt/hla). Among them, only B*51011 is well represented in most major ethnic groups (4,5). Here we present the nucleotide sequence of a novel HLA-B*51 variant, which differs from the predominant HLA- B*51011 allele by a single coding nucleotide change at exon 4. The new HLA-B*51 variant was detected during the HLA se- quence-based typing (SBT) of a Spanish Caucasoid organ donor (SBT kits and the Matchmaker Allele Identification, Applied Bios- ystems, Foster City, CA). The HLA-A, C, DRB1, DRB3 and DQB1 specificities were unambiguously assigned as A*02011, Cw*12031, Cw*15021, DRB1*11011, DRB1*13011, DRB3*0101, DRB3*0202, and DQB1*0603, DQB1*0301, respectively. The sequence analysis of HLA-B exon 2 and 3 gave a perfect match with the B*3801 and B*51011 combination. However, the inclusion of the exon 4 sequence in the same analysis resulted in an ambiguous HLA-B profile due to the presence of a nucleotide mismatch at position 787 (Fig.1). To resolve this ambiguity, a 2-kb amplicon encompassing the complete Authors’ affiliations: I. Gimferrer 1 , M. T. Arias 1 , V. Fabregat 1 , J. Martorell 2 , J. Vives 1 , F. Lozano 1 1 Institut Clı ´nic d’Infeccions i Immunologia (ICII), Institut d’Investigacions Me `diques August Pi i Sunyer (IDIBAPS), Hospital Clı ´nic, Barcelona, Spain Correspondence to: Francisco Lozano Servei d’Immunologı ´a Hospital Clı ´nic Villarroel 170 08036 Barcelona Spain Tel: π3493 4544920 Fax: π3493 4518038 e-mail: lozano/medicina.ub.es