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Open Access Research

Functional analysis of the interferon-stimulated response element of porcine circovirus type 2 and its role during viral replication in vitro and in vivo

Jinyan Gu, Yu Zhang, Xue Lian, Hailiang Sun, Jingman Wang, Weiting Liu, Gang Meng, Peng Li, Dan Zhu, Yuexin Jin and Ruibing Cao*

Author Affiliations

Key Laboratory of Animal Diseases Diagnostic and Immunology, Ministry of Agriculture, College of Veterinary Medicine, Nanjing Agriculture University, Tong Wei Road 6#, Nanjing 210095, Jiangsu, China

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Virology Journal 2012, 9:152  doi:10.1186/1743-422X-9-152

Published: 7 August 2012

Abstract

Background

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.

Methods

In 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.

Results

A 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.

Conclusions

These 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.

Keywords:
PCV2; Prep; ISRE; IFN-α; Replication; Regulation