An IMS 1313-Based Inactivated PRV Vaccine with a novel immunopotentiator induces Robust Protective Immunity against Virulent Variants.

BACKGROUND: Pseudorabies virus (PRV) variants have emerged as major swine pathogens associated with high piglet mortality and reproductive losses in China since 2011. Conventional oil-adjuvant vaccines are effective but frequently induce adverse local reactions. Water-soluble adjuvants, such as the nano-adjuvant IMS 1313, confer improved safety and potent immunogenicity. This study aimed to develop an inactivated PRV vaccine based on IMS 1313 combined with an immunopotentiator and evaluate its immune protective efficacy. METHODS: Multiple adjuvant-immunopotentiator combinations were screened. The PRV LA1206-80 strain formulated with IMS 1313 plus immunopotentiator c exhibited the optimal comprehensive performance and was selected for subsequent evaluation. Mice were immunized to detect serum neutralizing antibody titers and survival-based protection rates. Piglets were immunized via intramuscular or intradermal routes, and immune responses, post-challenge viral shedding, as well as histopathological lesions were monitored. Oil-adjuvant inactivated vaccine and live attenuated vaccine were set as control groups. Virus neutralization assays were performed to determine neutralizing antibody responses. RESULTS: After two immunizations with a 28-day interval, the IMS 1313 + immunopotentiator c formulation induced a neutralizing antibody titer of 1:32 and achieved 93.3 % protection in mice, which was markedly higher than that of the control groups (1:5.6). In this preliminary exploratory piglet trial, intramuscular vaccination yielded peak neutralizing antibody titers of 1:295.8, which appeared higher than those of the oil‑adjuvant vaccine (1:28.2) and live vaccine (1:13.1). This immunization regimen achieved 100 % survival, accompanied by reduced viral shedding and minimal pathological lesions. Intradermal vaccination conferred relatively lower protective efficacy, underscoring the critical influence of immunization route. CONCLUSION: IMS 1313 combined with immunopotentiator c markedly enhances the immunogenicity and safety profile of inactivated PRV vaccines in mice. Preliminary data from piglets revealed favourable protective trends upon intramuscular vaccination. This candidate represents a promising safer alternative compared with conventional oil-adjuvant vaccines and warrants further larger-scale efficacy evaluation.