Abstract
BackgroundPorcine circovirus 2 is the primary agent responsible for inducing a group of associated diseases known as Porcine Circovirus Associated Diseases (PCVAD), which can have detrimental effects on production efficiency as well as causing significant mortality. The objective of this study was to evaluate variation in viral replication, immune response and growth across pigs (n = 974) from different crossbred lines. The approach used in this study was experimental infection with a PCV2b strain of pigs at an average of 43 days of age.ResultsThe sequence of the PCV2b isolate used in the challenge was similar with a cluster of PCV2b isolates known to induce PCVAD and increased mortality rates. The swine leukocyte antigen class II (SLAII) profile of the population was diverse, with nine DQB1 haplotypes being present. Individual viremia and antibody profiles during challenge demonstrate variation in magnitude and time of viral surge and immune response. The correlations between PCV2 specific antibodies and average daily gain (ADG) were relatively low and varied between - 0.14 to 0.08 for IgM and −0.02 and 0.11 for IgG. In contrast, PCV2 viremia was an important driver of ADG decline following infection; a moderate negative correlation was observed between viral load and overall ADG (r = − 0.35, P < 0.001). The pigs with the lowest 10% level of viral load maintained a steady increase in weekly ADG (P < 0.0001) compared to the pigs that had the 10% greatest viral load (P < 0.55). In addition, the highly viremic group expressed higher IgM and IgG starting with d 14 and d 21 respectively, and higher tumor necrosis factor – alpha (TNF-α) at d 21 (P < 0.005), compared to low viremic group.ConclusionsMolecular sources of the observed differences in viremia and immune response could provide a better understanding of the host factors that influence the development of PCVAD and lead to improved knowledge of swine immunity.Electronic supplementary materialThe online version of this article (doi:10.1186/s12917-014-0286-4) contains supplementary material, which is available to authorized users.
Highlights
Porcine circovirus 2 is the primary agent responsible for inducing a group of associated diseases known as Porcine Circovirus Associated Diseases (PCVAD), which can have detrimental effects on production efficiency as well as causing significant mortality
Using an expansive array of swine germplasm analyzed, covering a significant proportion of the NorthAmerican maternal genetic crossbreds, in this study we evaluated phenotypic profiles, intra-populational variations and relationships between important indicators of PCV2 susceptibility
The potential role of swine leukocyte antigen class II (SLAII) region in immune response against swine viral pathogens was recently demonstrated by Quantitative Trait Loci (QTL) mapped to the SLAII region and associated with PCV2 viremia [7] and with specific antibody response to Porcine reproductive and respiratory syndrome virus (PRRSV) [9]
Summary
Porcine circovirus 2 is the primary agent responsible for inducing a group of associated diseases known as Porcine Circovirus Associated Diseases (PCVAD), which can have detrimental effects on production efficiency as well as causing significant mortality. Recent research has shown that host genotype influences PCV2 susceptibility, PCV2 viremia and immune response in experimental infections with PCV2b [7]. Using an expansive array of swine germplasm analyzed, covering a significant proportion of the NorthAmerican maternal genetic crossbreds, in this study we evaluated phenotypic profiles, intra-populational variations and relationships between important indicators of PCV2 susceptibility. This represents an essential preliminary step of the future research aimed at uncovering genetic variants that influence the host’s ability to stimulate immune response and reduce disease susceptibility
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