Protection of Piglets with Maternally Derived Antibodies from Sows Inoculated with an Attenuated Live Marker Classical Swine Fever Vaccine (Flc-LOM-BE(rns))

Here, we investigated the protective efficacy provided by passive immunity induced by a classical swine fever (Flc-LOM-BE(rns)) vaccine with the newly developed DIVA (Differentiating Infected from Vaccinated Animals) function. Ten pigs (aged 40–60 days) with maternally derived antibodies (MDAs) obtained from sows inoculated with the Flc-LOM-BE(rns) vaccine were challenged with virulent classical swine fever virus (CSFV). Pigs with an MDA titer of 6 log(2) induced by the Flc-LOM-BE(rns) vaccine were fully protected against virulent CSFV challenge but not the pigs with an MDA titer under 5 log(2). In addition, Flc-LOM-BE(rns) vaccine-derived MDAs successfully differentiated vaccinated pigs by bovine viral diarrhea virus (BVDV) E(rns)/CSFV E(rns) antibody detection, functioning as a DIVA.