Abstract
Classical swine fever virus (CSFV) infection leading to CSF outbreaks is among the most devastating swine diseases in the pig industry. Porcine circovirus type 2 (PCV2) infection, resulting in porcine circovirus-associated disease (PCVAD), is also a highly contagious disease affecting pig health worldwide. To prevent and control disease occurrence, multiple-vaccine immunization is necessary in contaminated areas or countries. In this study, a novel CSFV-PCV2 bivalent vaccine was constructed and demonstrated to be capable of eliciting humoral and cellular immune responses against CSFV and PCV2, respectively. Moreover, a CSFV-PCV2 dual-challenge trial was conducted on specific-pathogen-free (SPF) pigs to evaluate vaccine efficacy. All of the vaccinated pigs survived and showed no clinical signs of infection throughout the experimental period. In contrast, placebo-vaccinated pigs exhibited severe clinical signs of infection and steeply increased viremia levels of CSFV and PCV2 after virus challenge. Additionally, neither clinical signs nor viral detections were noted in the sentinel pigs when cohabitated with vaccinated-challenged pigs at three days post-inoculation of CSFV, indicating that the CSFV-PCV2 bivalent vaccine completely prevents horizontal transmission of CSFV. Furthermore, conventional pigs were utilized to evaluate the application of the CSFV-PCV2 bivalent vaccine in field farms. An adequate CSFV antibody response and a significant decrease in PCV2 viral load in the peripheral lymph nodes were observed in immunized conventional pigs, suggesting its potential for clinical application. Overall, this study demonstrated that the CSFV-PCV2 bivalent vaccine effectively elicited protective immune responses and the ability to prevent horizontal transmission, which could be a prospective strategy for controlling both CSF and PCVAD in commercial herds.