MOLECULAR CHARACTERIZATION OF SWINE LEUKOCYTE ANTIGEN (SLA) CLASS I GENES IN OUTBRED PIG POPULATIONS

Authors: HO, C - UNIV. OF MICHIGAN; Lunney, Joan; FRANZO-ROMAIN, M - UNIV. OF MICHIGAN; MARTENS, G - BAYLOR UNIV MED CENTER; LEE, Y - CHUNGNAM NATIONAL UNIV; LEE, J - CHUNGNAM NATIONAL UNIV; Wysocki, Michal; ROWLAND, R - KANSAS STATE UNIVERSITY; SMITH, D - UNIV. OF MICHIGAN

Submitted to: Animal Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/28/2008
Publication Date: 3/20/2009
Citation: Ho, C.S., Lunney, J.K., Franzo-Romain, M.H., Martens, G.W., Lee, Y.J., Lee, J.H., Wysocki, M., Rowland, R.R., Smith, D.M. 2009. Molecular characterization of swine leukocyte antigen (SLA) Class I of swine leukocyte antigen antigen (SLA) in outbred pig populations. Animal Genetics. 40:468-478.

Interpretive Summary: Responses to infectious diseases, vaccines, and organ transplants are determined by a set of genes, the major histocompatibility complex (MHC) or, for swine, the swine leukocyte antigen (SLA) genes. These genes have evolved to be highly polymorphic to bind numerous foreign antigens. To determine the numerous SLA genetic alleles effective techniques must be developed and be accurate. This manuscript documents the simple and rapid method developed to type alleles at the multiple SLA class I genes, and to specifically type alleles at each of the three classical SLA class I loci (designated SLA-1, SLA-3 and SLA-2). The method involves using the polymerase chain reaction (PCR)-sequence-specific primer (PCR-SSP) strategy. To be able to determine as many alleles as possible a set of PCR-SSP reactions was established to cover the currently known SLA class I alleles. Thus a PCR-SSP typing system with 47 discriminatory PCR primer pairs was designed to amplify the current SLA class I alleles based on groups that have similar sequence motifs. This manuscript reports our results in applying this low-resolution group-specific typing method to characterize the SLA class I alleles present in 202 pigs from three outbred pig populations. Overall 24 class I allele groups corresponding to 56 class I genotypes were detected; additionally 23 low-resolution SLA class I haplotypes were identified in these pigs. Two sets of SLA alleles, termed haplotypes were found in all three pig populations with a high prevalence; these were Lr-1.0 (SLA-1*01XX-SLA-3*01XX-SLA-2*01XX) and Lr-4.0 (SLA-1*04XX-SLA-3*04XX-SLA-2*04XX). Over 80% of the pigs examined (n = 162) were found to bear at least one of these SLA haplotypes, resulting in a combined haplotype frequency of nearly 50%. In summary this PCR-SSP-based typing system is a reliable and unambiguous method for detecting SLA class I alleles. It will now be available to investigate SLA diversity in outbred pig populations and help determine whether SLA class I alleles determine infectious disease responses or organ graft survival. Use of these molecular SLA typing methods will facilitate studies on the influence of SLA alleles on the development of effective vaccines and help identify the role of SLA antigens in disease-resistant pigs.

Technical Abstract: The highly polymorphic swine leukocyte antigen (SLA) genes are one of the most important determinants in swine immune responses to infectious diseases, vaccines, and in transplantation. Study of SLA influence requires accurate and effective typing methods. We developed a simple and rapid method to type alleles at the three classical SLA class I loci (SLA-1, SLA-3 and SLA-2) using the PCR-sequence-specific primer (PCR-SSP) strategy. This typing system relies on 47 discriminatory PCR primer pairs designed to amplify the SLA class I alleles by groups that have similar sequence motifs. We applied this low-resolution group-specific typing method to characterize the SLA class I alleles present in three outbred pig populations (n = 202). Alleles from 24 class I allele groups corresponding to 56 class I genotypes were detected. We also identified 23 low-resolution SLA class I haplotypes in these pigs and found haplotypes Lr-1.0 (SLA-1*01XX-SLA-3*01XX-SLA-2*01XX) and Lr-4.0 (SLA-1*04XX-SLA-3*04XX-SLA-2*04XX) in all three pig populations with a high prevalence. Over 80% of the pigs examined (n = 162) were found to bear at least one of these haplotypes, resulting in a combined haplotype frequency of nearly 50%. This PCR-SSP-based typing system demonstrates a reliable and unambiguous detection of SLA class I alleles, and can be used to effectively investigate the SLA diversity in outbred pig populations. Use of these molecular SLA typing methods will facilitate studies on the influence of SLA alleles on the development of effective vaccines and help identify the role of SLA antigens in disease-resistant pigs.