MAPPING DISEASE RESISTANCE GENES IN PIGS

Joan K. Lunney, Ph.D. Research Leader Immunology and Disease Resistance Laboratory LPSI, ARS, USDA Building 1040, Room 107 Beltsville, MD 20705 USA

This presentation will summarize the current public data on disease resistance genes that have been mapped in pigs. There are really few fully characterized genes that are known to endow disease resistance in pigs. The E. coli receptor genes are among the few mapped and fully characterized genes; they enable pigs to be completely resistant to infections with different strains of this pathogen, due to the lack of expression of intestinal receptors. Many other genes are known to be involved in enhancing or decreasing pathogen resistance or anti-tumor responses. Genes mapping to the major histocompatibility complex (MHC or swine leukocyte antigens, SLA) genes at the centromere of SSC7 have clearly been demonstrated to alter responses to viral and parasitic infections, to vaccines and to increase melanoma tumor regression. Comparative mapping has led to the identification of porcine MX, NRAMP and other genes associated with infectious disease resistance in mice. Maps of immune associated genes, e.g., immunoglobulin, T cell receptor, CD antigens, cytokine and cytokine receptors, and functional activities represent good candidate genes for resistance to pathogens. Proof of actual disease resistance associated with specific alleles at these loci is in process for pigs. New approaches to using the pig as a biomedical model are likely to benefit from comparative mapping studies; the recent mapping of the breast cancer resistance gene (BRCA1) and MADH4 could open up new avenues of research into the complex genetic interactions controlling cancer susceptibility, and as will the mapping of LDLR mutations assist in understanding hypercholesterolemia and heart disease in swine and humans. Microarray technologies will generate substantial functional genomic information that should highlight the role of numerous expected and unexpected genes in disease resistance.