An increasing demand in livestock animal husbandry for intervention or emergency vaccination strategies requires a rapid onset of protection linked to prevention of infectious agent spread. Using the new recombinant parapoxvirus (PPV) Orf virus (ORFV) as a
vaccine expressing the CSFV E2
glycoprotein we demonstrate that a single intra-muscular application confers solid protection. In the prime only concept, multi-site application of the vector
vaccine turned out to be superior to single-site application as no
pyrexia occurred after virulent CSFV challenge and CSFV neutralizing serum
antibodies regularly were detectable before challenge. Vector virus vaccinated swine were able to cope with the lymphocyte and in particular B-cell depression in peripheral blood after challenge showing no clinical signs and no
viremia. Early after challenge CSFV-specific IFN gamma production (IFN-gamma) and high neutralizing serum antibody titers clearly differentiated naïve from vaccinated and protected animals. After CSFV challenge neutralizing serum
antibodies titers in vector vaccinated swine were significantly higher than those in sera from live
attenuated vaccine primed animals. Horizontal challenge virus transmission was prevented under strict sentinel isolation before mingling but not in next-door stables separated by a wooden barrier at the day of challenge. The presence of CSFV-specific pre-challenge serum
antibodies although in low titers is a good prognostic parameter for solid protection after ORFV vector vaccination even when a significant CSFV-specific IFN-gamma production was not detectable before challenge. A heterologous prime-boost regimen as a combination of prime with baculovirus-expressed
glycoprotein E2 followed by boost with the parapoxvirus vector turned out to be a better immune stimulant than a homologous prime/boost with the modified live CSFV
vaccine. A similar beneficial effect became evident when the challenge
infection mimicked the booster vaccination after a single PPV vector prime.