Abstract
Infectious disease is an important problem for animal breeders, farmers and governments worldwide. One approach to reducing disease is to breed for resistance. This linkage study used a Charolais-Holstein F2 cattle cross population (n = 501) which was genotyped for 165 microsatellite markers (covering all autosomes) to search for associations with phenotypes for Bovine Respiratory Syncytial Virus (BRSV) specific total-IgG, IgG1 and IgG2 concentrations at several time-points pre- and post-BRSV vaccination. Regions of the bovine genome which influenced the immune response induced by BRSV vaccination were identified, as well as regions associated with the clearance of maternally derived BRSV specific antibodies. Significant positive correlations were detected within traits across time, with negative correlations between the pre- and post-vaccination time points. The whole genome scan identified 27 Quantitative Trait Loci (QTL) on 13 autosomes. Many QTL were associated with the Thymus Helper 1 linked IgG2 response, especially at week 2 following vaccination. However the most significant QTL, which reached 5% genome-wide significance, was on BTA 17 for IgG1, also 2 weeks following vaccination. All animals had declining maternally derived BRSV specific antibodies prior to vaccination and the levels of BRSV specific antibody prior to vaccination were found to be under polygenic control with several QTL detected.Heifers from the same population (n = 195) were subsequently immunised with a 40-mer Foot-and-Mouth Disease Virus peptide (FMDV) in a previous publication. Several of these QTL associated with the FMDV traits had overlapping peak positions with QTL in the current study, including the QTL on BTA23 which included the bovine Major Histocompatibility Complex (BoLA), and QTL on BTA9 and BTA24, suggesting that the genes underlying these QTL may control responses to multiple antigens. These results lay the groundwork for future investigations to identify the genes underlying the variation in clearance of maternal antibody and response to vaccination.
Highlights
Infectious disease in livestock is a cause for great concern for both farmers and governments worldwide
More recently we have shown that polymorphisms in one of the primary candidate loci implicated in the control of immune responsiveness, the Major Histocompatibility Complex (MHC) DRB3 gene, accounts for a proportion of the variation seen in response to the Bovine Respiratory Syncytial Virus (BRSV) vaccine [26], most of the genetic variation was shown to be controlled by nonMHC genes
Of the 27 Quantitative Trait Loci (QTL) detected, 16 were associated with the IgG2 response, whilst 7 QTL were associated with the total IgG response and only 4 with the IgG1 response
Summary
Infectious disease in livestock is a cause for great concern for both farmers and governments worldwide. An understanding of the underlying genetics that control variation in immune responses and infectious disease outcomes may lead to the selection of more resistant animals, as well as identifying new strategies for improving vaccine efficacy. Bovine respiratory disease has a complex aetiology caused by many different pathogens including viruses and bacteria [2,3,4] and affects cattle world-wide, resulting in major welfare problems and economic losses [5]. Both dairy and beef cattle show a wide range of clinical signs related to BRD, including nasal discharge, coughing, fever and decreased appetite when infected. This evidence comes from field studies where the causal pathogen(s) were not identified, and the heritability of response to particular infections may be underestimated
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