Classical swine fever virus replicon particles lacking the E gene: a potential marker vaccine for intradermal applicationCaroline F. Frey, Oliver Bauhofer, Nicolas Ruggli, Artur Summerfield, Martin A. Hofmann and Jon-Duri Tratschin
Institute of Virology and Immunoprophylaxis, 3147 Mittelhäusern, Switzerland
(Received 17 November 2005; accepted 6 March 2006; published online 17 June 2006)
Abstract - Classical swine fever virus replicon particles (CSF-VRP) deficient for E were evaluated as a non-transmissible marker vaccine. A cDNA clone of CSFV strain Alfort/187 was used to obtain a replication-competent mutant genome (replicon) lacking the sequence encoding the 227 amino acids of the glycoprotein E (A187delE ). For packaging of A187delE into virus particles, porcine kidney cell lines constitutively expressing E of CSFV were established. The rescued VRP were infectious in cell culture but did not yield infectious progeny virus. Single intradermal vaccination of two pigs with 107 TCID50 of VRP A187delE elicited neutralizing antibodies, anti-E2 antibodies, and cellular immune responses determined by an increase of IFN- producing cells. No anti-E antibodies were detected in the vaccinees confirming that this vaccine represents a negative marker vaccine allowing differentiation between infected and vaccinated animals. The two pigs were protected against lethal challenge with the highly virulent CSFV strain Eystrup. In contrast, oral immunization resulted in only partial protection, and neither CSFV-specific antibodies nor stimulated T-cells were found before challenge. These data represent a good basis for more extended vaccination/challenge trials including larger numbers of animals as well as more thorough analysis of virus shedding using sentinel animals to monitor horizontal spread of the challenge virus.
Key words: pestivirus / classical swine fever virus / E / replicon / marker vaccine
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© INRA, EDP Sciences 2006