A PCR method for typing B-L̄II family (class II MHC) alleles in broiler chickens

Certain haplotypes of the major histocompatibility (B) complex are strongly associated with resistance or susceptibility to several infectious diseases in Leghorn chickens. Identification of chicken haplotypes based on the nucleotide sequence of B complex loci could provide more precise identification of haplotypes than traditional serological methods. We report the development and application of polymerase chain reaction with sequence specific primers (PCR-SSP) to type broiler chicken B haplotypes based on the DNA sequence of B-β3II family genes. Five well-defined standard B haplotypes from White Leghorns and 12 recently characterized B haplotypes from a broiler breeder line were used to develop the test system. The B-LβII family loci were amplified from genomic DNA by B-LβII family specific primers and then characterized by PCR-SSP. In total, ten pairs of primers, derived from the sequences of expressed B-LβII family alleles, were used in the PCR typing test to discriminate the Chicken B haplotypes identified previously by serological means. The PCR-SSP showed that each haplotype had a different amplification pattern, except those haplotypes known or suspected to have the same B-Lβ alleles. Cloning and sequencing of the family specific PCR products indicated that two loci in the B-LβII family, presumably B-LβI and B-LβII, were amplified. Finally, B-Lβ PCR-SSP typing was used in combination with B-G RFLP analyses to characterize unusual (variant) B serotypes; the results indicate that some of these are natural recombinants within the B complex.