Abstract
BackgroundPorcine circovirus type 2 (PCV2) is associated with post-weaning multi-systemic wasting syndrome (PMWS) in young weaned pigs. Immune stimulation was found to activate the replication of PCV2 and exacerbate the clinical outcome of the infection. Proper amount of interferon-α (IFN-α) is able to enhance PCV2 infection and production in Porcine kidney-15 (PK-15) cells when administered after inoculation.MethodsIn the present study, luciferase reporter assays, construction of mutant viruses, Analysis the replication efficiency and the response to IFN-α treatment in PK-15 cells and animal experiments were carried out to analyze the function of interferon-stimulated response element (ISRE) of PCV2 and its role during viral replication in vitro and in vivo.ResultsA functional viral ISRE sequence, 5′-CTGAAAACGAAAGA-3′, was identified in Rep gene promoter (Prep) of PCV2. PCV2 Prep is composed of two mini promoters, the proximal one span the sequence +1 to -106, containing an ISRE while the distal mini promoter is composed of three tandem GC box like sites locate at -85 to -194. It was demonstrated that viral ISRE is necessary for porcine IFN-α initiated luciferase expression enhancement and it plays an important role in affecting the replication efficiency of PCV2 in vivo and in vitro.ConclusionsThese findings provide a theoretical basis for the Phenomenon of immunostimulation is able to enhance PCV2 infection, and improve the understanding of the complicated mechanisms involved in the host and pathogen interactions of PCV2.
Highlights
Porcine circovirus type 2 (PCV2) is associated with post-weaning multi-systemic wasting syndrome (PMWS) in young weaned pigs
To determine whether the interferon-stimulated response element (ISRE) sequence in PCV2 Rep promoter is individual response to IFN-α treatment, the synthetic multiple viral ISRE was examined in the context of an enhancer test vector pGL-miniP. pGL-miniP was constructed by substituted the SV40 promoter of pGL3-Promoter with HSV-1 TATA-like promoter (PTAL)
The pGm-GBP-ISRE(3) constructs was proved to have similar, but somewhat greater, responsiveness to porcine IFN-α treatment, confirming that the PCV2 Rep promoter ISRE sequence can act as an interferon-stimulated response element in a manner similar to previously characterized ISRE-containing promoter [17]
Summary
Porcine circovirus type 2 (PCV2) is associated with post-weaning multi-systemic wasting syndrome (PMWS) in young weaned pigs. Immune stimulation was found to activate the replication of PCV2 and exacerbate the clinical outcome of the infection. Proper amount of interferon-α (IFN-α) is able to enhance PCV2 infection and production in Porcine kidney-15 (PK-15) cells when administered after inoculation. PCV2 was identified as an essential causative agent of post-weaning multi-system wasting-syndrome (PMWS) [1]. The disease most commonly affects pigs between the ages of 5–18 weeks, clinical signs include a marked increase in the mortality rate, wasting, generalized enlargement of. It is generally believed that immunostimulation either by vaccination or secondary viral infection plays a role in the occurrence of PMWS [4,5,6,7]. The exact role of immunostimulation in the progression to clinical PMWS is still unknown
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