title: HLA-B27 subtypes in Asian patients with ankylosing spondylitis. Evidence for new associations.
abstract: The aim of this study was to investigate the contribution of the different B27 subtypes to ankylosing spondylitis (AS) susceptibility. The polymerase chain reaction (PCR) in combination with the sequence-specific oligonucleotide probes (SSOs) was used to analyse the polymorphism in exon 2 and 3 of HLA-B27 in two Asian groups with different genetic HLA structures: Indian (I) and Thai (T) populations. The same number of AS patients (45) and healthy B27 positive donors (n = 17) from both populations were analysed in order to ascertain the B27 subtypes. Three different findings can be concluded from this study: 1) B*2707 has been found to be associated with AS in both populations. This association has not been previously reported in either ethnic group. 2) B*2704 is strongly associated with AS in the Thai patients (91% in AS vs. 47% in C; RR = 11.5; EF = 0.83). In contrast, B*2704 was found with similar frequency in Asian Indians AS patients and controls (41% in AS vs. 41% in C.). 3) B*2706 was found overrepresented in control populations and absent in AS patients (0% in AS vs. 47% in C.; pc < 10(-6)) showing the maximum value of protective fraction (PF = 1). The B*2706 negative association with AS has not been previously described in other ethnic groups and could indicate a protective effect of this subtype on AS susceptibility. The B*2706 allele has two changes relative to B*2704 at residue 114 (His to Asp) and 116 (Asp to Tyr) in the pockets D/E. The importance that these differences can play in the pathogenesis of AS are discussed.
authors.affiliation: Hospital Central de Asturias, Oviedo, Spain.
authors.forename: C
authors.initials: C
authors.lastname: López-Larrea
authors.forename: K
authors.initials: K
authors.lastname: Sujirachato
authors.forename: N K
authors.initials: NK
authors.lastname: Mehra
authors.forename: P
authors.initials: P
authors.lastname: Chiewsilp
authors.forename: D
authors.initials: D
authors.lastname: Isarangkura
authors.forename: U
authors.initials: U
authors.lastname: Kanga
authors.forename: O
authors.initials: O
authors.lastname: Dominguez
authors.forename: E
authors.initials: E
authors.lastname: Coto
authors.forename: M
authors.initials: M
authors.lastname: Penã
authors.forename: F
authors.initials: F
authors.lastname: Setién
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D016022:Case-Control Studies; D004247:DNA / Q000097:blood; D015343:DNA Probes, HLA; D005787:Gene Frequency; D005805:Genes, MHC Class I / Q000235:genetics*; D015796:HLA-B27 Antigen / Q000145:classification / Q000235:genetics*; D006801:Humans; D007194:India; D008969:Molecular Sequence Data; D017354:Point Mutation; D016133:Polymerase Chain Reaction; D011487:Protein Conformation; D013167:Spondylitis, Ankylosing / Q000208:ethnology / Q000235:genetics*; D013785:Thailand
chemical_list: D015343:DNA Probes, HLA; D015796:HLA-B27 Antigen; D004247:DNA