Assessment of the Safety Profile of Chimeric Marker Vaccine against Classical Swine Fever: Reversion to Virulence Study.

Chimeric marker vaccine candidates, vGPE - /PAPeV E rns and vGPE - /PhoPeV E rns , have been generated and their efficacy and capability to differentiate infected from vaccinated animals were confirmed in previous studies. The safety profile of the two chimeric marker vaccine candidates, particularly in the potential reversion to virulence, was evaluated. Each virus was administered to pigs with a dose equivalent to the vaccination dose, and pooled tonsil homogenates were subsequently inoculated into further pigs. Chimeric virus vGPE - /PAPeV E rns displayed the most substantial attenuation, achieving this within only two passages, whereas vGPE - /PhoPeV E rns was detectable until the third passage and disappeared entirely by the fourth passage. The vGPE - strain, assessed alongside, consistently exhibited stable virus recovery across each passage without any signs of increased virulence in pigs. In vitro assays revealed that the type I interferon-inducing capacity of vGPE - /PAPeV E rns was significantly higher than that of vGPE - /PhoPeV E rns and vGPE - . In conclusion, the safety profile of the two chimeric marker vaccine candidates was affirmed. Further research is essential to ensure the stability of their attenuation and safety in diverse pig populations.