Servicio de Información Comunitario sobre Investigación y Desarrollo - CORDIS

Recombinant CSFV vaccine in parapoxvirus ovis vector (ORFV D1701VrVE2)

Recombinant parapoxvirus Orf virus (ORFV) has been developed as a safe and immuno-stimulatory vector expressing the CSFV protein E2 (ORFV D1701VrVE2). Since the NS3 subunit of CSFV turned out to be non-protective neither when applied as coding plasmid DNA nor as E. coli expressed protein the construction of NS3 expressing recombinant ORFV was not included. Instead ORFV D1701VrVE2 vaccine application and delivery experiments were the main focus of the project with respect to this TIP. ORFV D1701VrVE2 was shown to be completely avirulent for pigs. The vector is a potent stimulator of IFN-a and VSV antiviral activity in porcine PBMC. In several animal immunisation experiments with swine ORFV D1701VrVE2 induced CSFV-neutralizing serum antibodies already after a single application. Immunized piglets were protected against lethal CSFV challenge and did not develop fever. Vaccinated and challenged animals recovered from the characteristic CSFV-induced B-cell reduction. The distribution of the vaccine dose over four intra-muscular injection sites (multi-site application) led to a rapid induction of neutralizing antibodies and to solid protection from CSF after a single vaccination. In contrast to single site-vaccinated animals, multi-site vaccinated piglets did not transmit the challenge virus to a naive sentinel.

Two successive vector virus applications in a homologous prime-boost regimen did not provoke IFN-? producing cells among PBMC. However, a heterologous prime-boost regimen as a combination of prime with baculovirus expressed glycoprotein E2 followed by boost with the parapoxvirus vector induced high numbers of IFN-? producing cells. A similar beneficial effect became evident when the challenge infection mimicked the booster vaccination after a single vector prime. In contrast when the challenge CSFV was applied after a homologous prime with modified live CSFV vaccine the immunised piglets responded with lower numbers of IFN-? producing cells as well as significantly lower titres of CSFV-neutralizing serum antibodies. In conclusion, the project discovered that ORFV D1701VrVE2 was an efficient vaccine, inducing solid protection and preventing virus shedding. It was completely avirulent for pigs, and the vector is a potent stimulator of IFN-a.

CSFV-neutralizing serum antibodies were induced after a single application, and immunized piglets were completely protected against lethal CSFV challenge. A multi-site application of the vaccine led to the most rapid induction of neutralizing antibodies plus solid protection, and prevented transmission of the challenge virus to naive sentinels.

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