M. Mellencamp

Traits associated with innate and adaptive immunity in pigs: heritability and associations with performance under different health status conditions.

There is a need for genetic markers or biomarkers that can predict resistance towards a wide range of infectious diseases, especially within a health environment typical of commercial farms. Such markers also need to be heritable under these conditions and ideally correlate with commercial performance traits. In this study, we estimated the heritabilities of a wide range of immune traits, as potential biomarkers, and measured their relationship with performance within both specific pathogen-free (SPF) and non-SPF environments. Immune traits were measured in 674 SPF pigs and 606 non-SPF pigs, which were subsets of the populations for which we had performance measurements (average daily gain), viz. 1549 SPF pigs and 1093 non-SPF pigs. Immune traits measured included total and differential white blood cell counts, peripheral blood mononuclear leucocyte (PBML) subsets (CD4+ cells, total CD8α+ cells, classical CD8αβ+ cells, CD11R1+ cells (CD8α+ and CD8α-), B cells, monocytes and CD16+ cells) and acute phase proteins (alpha-1 acid glycoprotein (AGP), haptoglobin, C-reactive protein (CRP) and transthyretin). Nearly all traits tested were heritable regardless of health status, although the heritability estimate for average daily gain was lower under non-SPF conditions. There were also negative genetic correlations between performance and the following immune traits: CD11R1+ cells, monocytes and the acute phase protein AGP. The strength of the association between performance and AGP was not affected by health status. However, negative genetic correlations were only apparent between performance and monocytes under SPF conditions and between performance and CD11R1+ cells under non-SPF conditions. Although we cannot infer causality in these relationships, these results suggest a role for using some immune traits, particularly CD11R1+ cells or AGP concentrations, as predictors of pig performance under the lower health status conditions associated with commercial farms.

Characterisation of plasma acute phase protein concentrations in a high health boar herd

Acute phase proteins (APP) are used as markers of inflammation and sub-clinical disease and are considered potential biomarkers for pig health and welfare. However, reference ranges for their baseline concentrations are necessary before their use can be considered in routine herd health. In this study, C-reactive protein (CRP), haptoglobin (Hp), pig-major acute-phase protein (Pig-MAP) and transthyretin (TTR) baseline concentrations were determined in boars from a high health commercial herd and differences between seven commercial breeding lines within the herd were investigated. Reference ranges of 3.6-183 mg/L for CRP, 0.01-1.31 g/L for Hp, 0.32-2.9 g/L for Pig-MAP and 174-610 mg/L for TTR were found. Correlations were determined between Hp and CRP, Hp and Pig-MAP and CRP and Pig-MAP. Additionally, significant differences were found among the concentrations of CRP, Pig-MAP and TTR in seven commercial breeding lines.

Dynamic Differential Regulation of Innate Immune Transcripts during the Infection of Alveolar Macrophages by the Porcine Reproductive and Respiratory Syndrome Virus

Porcine reproductive and respiratory syndrome virus (PRRSV), an arterivirus, is the etiologic agent of an infectious disease of that name, characterized by respiratory disorders, abortion in pregnant sows and high mortality in piglets, resulting in significant economic losses in the pig industry worldwide. In order to identify whether genetic differences in PRRSV response may exist in pigs, alveolar macrophages were used to assess the progression of the type-I interferon (IFN) transcript response in porcine alveolar macrophages infected by PRRSV. Our results suggest that a dynamic differential regulation of the type-I IFN and chemokine transcripts may operate during the first hours of infection with and entry of the virus in alveolar macrophages, and provide a compelling mechanism for the establishment of PRRSV replication in susceptible cells.

Associations between Polymorphisms in the Porcine Haptoglobin Gene and Baseline Levels of Serum Haptoglobin

Haptoglobin (Hp) is an acute phase protein that is a marker in blood for clinical and subclinical disease in the pig. The aim of this study was to identify single nucleotide polymorphisms (SNPs) in the Hp gene and analyse their influence on baseline serum levels. DNA samples and serum were collected from 345 boars. Of 13 SNPs identified, 5 were genotyped using PCR-RFLP and Pyrosequencing. Serum Hp levels were measured using a biochemical assay. A general linear model was fitted with line and genotype as fixed effects. In addition, linkage disequilibrium (LD) was estimated between the 5 SNPs using r-square and D prime. Serum Hp concentrations in the population showed a skewed distribution with a mean of 0.34 g/L (range 0-2.65 g/L). Three SNPs were found to be associated with baseline Hp levels (p-value = 0.0093, 0.0051 and 0.0094). These 3 SNPs were also found to be in high LD with each other. This is the first study to find associations between polymorphisms in the porcine Hp gene and baseline Hp serum levels. The results have implications for breeding for resistance to infection.