Evaluation of an E2-based indirect ELISA for the serological differentiation of ovine Italy pestivirus from classical swine fever virus in pigs.

The genus Pestivirus includes several species responsible for economically important diseases in domestic and wild animals. In 2017, a novel ovine pestivirus (ovIT PeV) was isolated from aborted lamb fetuses and molecular analysis showed a genetic distinction from known Pestivirus species with the closest phylogenetic relationship to classical swine fever virus (CSFV, Pestivirus suis). This close similarity is concerning because CSF is a notifiable disease to the World Organization for Animal Health (WOAH) and is subject to eradication campaigns. Moreover, ovIT PeV can infect pigs and induce an early strong immune response that can cause false-positive results in CSF antibody ELISAs used for CSF surveillance. Our study aimed to develop an indirect ELISA (iELISA) to serologically distinguish ovIT PeV from CSFV in pigs. Hence, we expressed the recombinant E2 glycoproteins of ovIT PeV and CSFV (strain Diepholz) in mammalian cells. Two E2 iELISAs were evaluated using a panel of CSFV, ovIT PeV and negative pig sera. Each serum showed higher antibody titres in the iELISA with the homologous antigen rather than the heterologous one. This study highlighted the effectiveness of using virus-specific antigens and comparing antibody titres when assessing infections with serologically cross-reactive viruses.