Analyses of immune competence traits and their association with candidate genes in pigs (English shop)

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The present study was carried out to investigate the immune competences of a
backcross DUMI population. Complement activity via classical and alternative
pathways were determined using haemolytic activity assay. Antibodies response to
Mycoplasma hyopneumoniae, Tetanus toxoid and PRRS virus were determined using an
Enzyme-Linked Immunosorbent Assay (ELISA). Moreover, complement component
C3c and Haptoglobin (Hp), the important parameters of animal immune response were
also determined. The parameters were further utilized as phenotypes for the linkage
mapping to detect quantitative trait loci (QTL). Microsatellite genotyping was employed
to detect the QTL of the immune traits. A total of 220 backcross animals were used for
QTL analysis. Seventy-four microsatellites from 18 autosomes of Sus scrofa have been
used for QTL mapping. Forty-two significant and twenty-four highly significant QTL
could be detected for all immune traits. Most QTL were detected on SSC3, SSC16, and
SSC18 (nine significant F-values on each chromosome). No significant F-value was
detected on SSC12 and SSC13. Highly significant QTL could be detected for antibody
response to Mycoplasma, Tetanus and PRRS vaccination, C3c and Hp concentration.
For AH50 and CH50, twenty-two significant and nine highly significant QTL could be
detected by using the program QTL express. Mannose-binding lectin (MBL) genes were
proposed as a candidate gene in this study. Two porcine genes MBL1 and MBL2 were
investigated. A phylogenetic study revealed that the porcine MBL genes had higher
identities to bovine rather than primate and rodent sequences. Both genes were assigned
to chromosome 14 by the radiation hybrid panel and linkage mapping. Both MBL genes
were highly expressed in liver. MBL1 was also found to be expressed in lung, testis and
brain, while low expression of MBL2 was detected in testis and kidney. New single
nucleotide polymorphisms (SNP) of the porcine MBL2 gene were found and genotyped
in an experimental F2 pig population together with a previously reported SNP of MBL1.
MBL1 genotypes differed in C3c serum concentration, i.e. in vivo complement activity,
at p<0.1. Correspondingly, linkage analysis revealed a QTL for C3c serum level close to
the position of the MBL genes. The study thus promotes the porcine MBL genes as
functional and positional candidate genes for complement activity.