Swine Leukocyte Antigen-<italic>DQA</italic> Gene Variation and Its Association with Piglet Diarrhea in Large White, Landrace and Duroc

Abstract

The swine leukocyte antigen class II molecules are possibly associated with the induction of protective immunity. The study described here was to investigate the relationship between polymorphisms in exon 2 of the swine DQA gene and piglet diarrhea. This study was carried out on 425 suckling piglets from three purebred pig strains (Large White, Landrace and Duroc). The genetic diversity of exon 2 in swine DQA was detected by PCR-SSCP and sequencing analysis, eight unique SSCP patterns (AB, BB, BC, CC, CD, BD, BE and DD) representing five specific allele (A to E) sequences were detected. Sequence analysis revealed 21 nucleotide variable sites and resulting in 12 amino acid substitutions in the populations. A moderate level polymorphism and significant deviations from Hardy-Weinberg equilibrium of the genotypes distribution were observed in the populations (p<0.01). The association analysis indicated that there was a statistically significant difference in the score of piglet diarrhea between different genotypes, individuals with genotype CC showed a lower diarrhea score than genotypes AB (0.98±0.09), BB (0.85±0.77) and BC (1.25±0.23) (p<0.05), and significantly low than genotype BE (1.19±0.19) (p<0.01), CC genotype may be a most resistance genotype for piglet diarrhea.

Polymorphism and haplotype analyses of swine leukocyte antigen DQA exons 2, 3, 4, and their associations with piglet diarrhea in Chinese native pig

“…Bao et al (2012) found that SLA-DQA was broadly expressed in 11 piglet tissues, which may enhance humoral immunity and cell immunity to reduce signal transduction of F18 bacteria, and improved disease resistance. Yang et al (2013Yang et al ( , 2014 found that the various DQA and DRA genotypes significantly influenced the piglet diarrhea. Exploring the genetic influence on animal diseases can be used to effectively identify and control livestock diseases to reduce disease costs and increase animal health (Mallard et al, 1991;Eveline et al, 2008).…”

Genetic association of sequence variation in exon 3 of the swine leukocyte antigen-DQA gene with piglet diarrhea in Large White, Landrace, and Duroc piglets

“…In addition, a high PIC value (>0.67) was observed at this locus in the three breeds, which provides further evidence that exon 3 is highly polymorphic. Of the 17 nucleotide variants found in exon 3, eight (c.4672A>C, c.4680T>C, c.4691T>C, c.4732G>A, c.4746C>T, c.4802T>C, c.4803C>T, and c.4806T>C) were novel, which was a greater number of DQA alleles than was found in exon 2 in a previous study (Yang et al, 2013). Liu et al (Liu LX, Gun SB, Zhao SG, Lu HN, et al, unpublished results) identified four nucleotide variants (c.4618T>C, c.4635A>G, c.4673G>A, and c.4760G>A) and three nucleotide deletions (c.4727-4729 CAG) that formed only three alleles in 471 Bamei, Juema, and Gansu Black pigs (GenBank accession Nos.…”

“…Heterozygosity of BoLA-DQA1 is associated with resistance to proviral bovine leukemia in Japanese Black cattle (Miyasaka et al, 2013) and mastitis in dairy cattle (Takeshima et al, 2008). Curiously, however, homozygous genotypes such as CC in exon 2 of DQA in Large White, Landrace, and Duroc pigs (Yang et al, 2013), DQA*03xa0303xa03 in exon 2 of DQA in Bamei, Juema, and Gansu Black pigs (Liu et al, 2015b), and BB in exon 2 of DQA in Yantai Black pigs are associated with low diarrheal scores, and are probably resistant genotypes. These results confirm the fact that resistant homozygotes play important roles in pathogen defense.…”

“…Ear tissue samples were collected from three introduced commercial pig strains (Large White, N = 148; Landrace, N = 146; Duroc, N = 131), as in our earlier study (Yang et al, 2013). The piglets used were the June 2010 progeny of 17 Large White, 17 Landrace, and 14 Duroc sows that were maintained under similar forage, feed management, and disease control systems, and were used to investigate the association between exon 2 of SLA-DQA and diarrhea.…”

“…This gene contains four exons and three introns: exon 1 encodes a signal peptide, exons 2 and 3 encode corresponding external cellular a1 and a2 domains, and exon 4 encodes both the transmembrane and cytoplasmic domains. Although recent study has increased our knowledge of the association between DQA exon 2 genetic variation and piglet diarrhea (Yang et al, 2013;Huang et al, 2015;Liu et al, 2015b), it is widely accepted that polymorphic loci do not act alone in determining disease resistance, but rather as part of an intrinsic network (Stumpf, 2004;Bahlo et al, 2006). As both SLA-DRA and SLA-DRA-DQA haplotypes are linked to diarrhea resistance in Large White, Landrace, Duroc, and Yantai Black piglets (Yang et al, 2014, it is probable that variants in additional SLA-DQA exon coding regions act as a linked intrinsic network to contribute to diarrhea disease.…”