Foot-and-Mouth Disease Virus Persistence Divergence Within Serotypes and Vaccine Doses in Vaccinated Cattle

Foot-and-mouth disease virus (FMDV) persistence in ruminants constitutes the potential risk of disease transmission. While vaccination effectively protects animals against clinical disease, more than 50% of vaccinated cattle can still develop persistent infection. Investigating the potential factors that influence the establishment of FMDV persistence in vaccinated cattle is critical for improving control and eradication strategies in epidemic regions. Here, cattle vaccinated with different doses of serotype O and serotype A vaccines were experimentally challenged with the homologous virus. The overall incidence of the carrier state was 22.5%. Although higher levels and prolonged detection of viral RNA in oesophagal-pharyngeal fluids (OPFs) were observed in the two higher-dose groups of both serotypes, neither viral serotype nor vaccine dose significantly influenced the final carrier incidence. Notably, most carriers showed a slower rise in antigen-specific and neutralizing antibody (NAb) titers postchallenge, resulting in significantly lower antibody titers during the early infection stage, irrespective of the viral serotypes or vaccine doses. Viral genomes and particles were predominantly localized within nasopharyngeal tissues, including the nasopharynx, soft palate, and adjacent lymph nodes and tonsils. In addition, carriers exhibited an increased number of germinal centers in the lymph nodes and tonsils. These findings provide novel insights into the immunological features associated with FMDV persistence in vaccinated cattle and offer a theoretical foundation for optimizing vaccine design and developing targeted immune intervention strategies.