Dissection of Porcine MHC Polymorphisms to Improve Pig's Resistance on Pathogenic Challenge

The genetic improvement of animals to cope with pathogenic challenge and to increase host resistance against pathogens should improve the productivity of pig production and animal welfare. To understand the differences in immune responses attributed to genetic differences should provide means to enhance host capacity to control disease causing agents. Swine leukocyte antigen (SLA) genes, the most polymorphic genes of the pig genome, code for molecules that present self and non-self antigens to T cells and trigger specific immune responses, thereby playing a crucial role in the immune system. Breeding animals with the best genetic configuration or haplotypes of SLA molecules for a specific environment or against a specific pathogen could be utilized as a method to improve animal health. However, effective methodsto type SLA molecules for field samples have not been available. Therefore, the studies to evaluatethe genetic diversity of pig MHC moleculeson diverse commercial pig breeds or populations have been limited. Recently, we characterized the genomic sequences of the epitope binding regions of major MHC genes from diverse individuals and developed the efficient and comprehensive genomic-sequence-based typing (GSBT) method for SLA class I and class II genes including SLA-1, -2, -3 and SLA-DQA, -DQB1 and –DRB1. We performed high resolution typing for more than 500 pigs of 7 different breeds and characterize the genetic characteristics and diversity of the pig MHC system. Our results showed that current knowledge on SLA diversity was very limited especially for class I genes. There were differences in allele frequency or distribution of MHC genes among different breeds. Further studies using a larger sample size are still necessary to illuminate the genetic diversity of SLA genes and allelic differences in a more detail level. The knowledge will benefit to learn differences in immune responses to foreign antigens by different MHC haplotypes, which could be applied to increase the disease tolerance of animals and to develop effective vaccines for major pathogens.