Molecular characterization of swine leukocyte antigen gene diversity in purebred Pietrain pigs.

The porcine major histocompatibility complex (MHC) harbors the highly polymorphic swine leukocyte antigen (SLA) class I and II gene clusters encoding glycoproteins that present antigenic peptides to T cells in the adaptive immune response. In Austria, the majority of commercial pigs are F 2 descendants of F 1 Large White/Landrace hybrids paired with Pietrain boars. Therefore, the repertoire of SLA alleles and haplotypes present in Pietrain pigs has an important influence on that of their descendants. In this study, we characterized the SLA class I ( SLA-1 , SLA-2 , SLA-3 ) and class II ( SLA-DRB1 , SLA-DQB1 , SLA-DQA ) genes of 27 purebred Pietrain pigs using a combination of the high-resolution sequence-based typing (SBT) method and a low-resolution (Lr) PCR-based method using allele-group, sequence-specific primers (PCR-SSP). A total of 15 class I and 13 class II haplotypes were identified in the studied cohort. The most common SLA class I haplotype Lr-43.0 ( SLA-1 *11XX- SLA-3 *04XX- SLA-2 *04XX) was identified in 11 animals with a frequency of 20%. For SLA class II, the most prevalent haplotype, Lr-0.14 [ SLA-DRB1 *0901- SLA-DQB1 *0801- SLA-DQA *03XX], was found in 14 animals with a frequency of 26%. Two class II haplotypes, tentatively designated as Lr-Pie-0.1 [ SLA-DRB1 *01XX/be01/ha04- SLA-DQB1 *05XX- SLA - DQA*blank] and Lr-Pie-0.2 [ SLA-DRB1 *06XX- SLA-DQB1 *03XX- SLA-DQA *03XX], appeared to be novel and have never been reported so far in other pig populations. We showed that SLA genotyping using PCR-SSP-based assays represents a rapid and cost-effective way to study SLA diversity in outbred commercial pigs and may facilitate the development of more effective vaccines or identification of disease-resistant pigs in the context of SLA antigens to improve overall swine health.