Defining the allelic variants of HLA-A30 in the Sardinian population using amplification refractory mutation system--polymerase chain reaction.

HLA-A30 is present in the Sardinian population at a frequency of 23%. We have designed a system using nested ARMS-PCR to determine the relative frequencies of the HLA-A30 allelic variants (A3001, A3002, and A3003) within this population. The use of a nested PCR approach, in which the first-round reaction provides HLA-A30 specificity and template DNA for the subsequent nested reactions, is a powerful means of discriminating between alleles of very similar sequence. Using this method, we performed subtyping of 35 serologically defined HLA-A30 Sardinian individuals, and taking into account homozygotes, identified 38 A30 alleles. Of these, 33 typed as A3002, four typed as A3001, and one sample did not conform to the patterns of reactivity of any of the published A30 alleles. Haplotype information showed strong linkage disequilibrium between A3002 and B18. This study underlines the potential of DNA-based methods for typing HLA class I in terms of adding further levels of definition to studies of population structure and also as a means of identifying new alleles.