Molecular and Replication Dynamic Profiling of Regionally Important Pestivirus bovis Subgenotypes from Hungary

This study investigated the in vitro replication kinetics and molecular characteristics of five field isolates of bovine viral diarrhea virus (BVDV) representing subgenotypes 1b, 1d, and 1f, currently circulating in Hungary. We compared cytopathogenic (cp) and non-cytopathogenic (ncp) biotype pairs using digital PCR (dPCR) and virus titration. While dPCR showed higher genome copy numbers for cp isolates, virus titration revealed comparable or lower infectious titers, suggesting the accumulation of replication-incompetent viral particles during the infection cycle. Molecular analysis identified (novel) amino acid substitutions in Npro, capsid, and NS4B regions, although typical large-scale genome rearrangements were absent. These findings demonstrate that biotype differences are molecularly complex and subgenotype-dependent. Our results emphasize that relying on a few genetic markers is insufficient for biotype categorization, necessitating comprehensive characterization in BVDV surveillance programs. This complexity must be considered when designing vaccines or control programs, especially in regions with diverse circulating strains.