Newcastle Disease Virus-Vectored African Swine Fever Virus Antigen Cocktail Delays the Onset of ASFV-SY18 but Is Not Protective.

African Swine Fever (ASF) is a highly contagious viral disease threatening the global pig industry. Currently, only two gene-deleted live attenuated vaccines are approved, exclusively in Vietnam, and their long-term effectiveness and safety are unproven, prompting the need for safer alternatives. This study assessed a cocktail of African Swine Fever Virus (ASFV) antigens delivered via a recombinant Newcastle Disease Virus (rNDV) vector against the genotype II ASFV-SY18. Antigens pB602L, pEP84R, and p22 (pKP177R) were selected based on virus neutralization and lymphocyte proliferation assays in mice and combined with capsid protein p72 (pB646L) for vaccination and challenge in pigs. The antigen cocktail delayed ASF symptoms by 3-4 days but did not prevent the lethal ASFV-SY18 infection. Significant ASFV-specific gamma interferon (IFN-γ) positive responses and NDV antibodies were detected post-inoculation, showing an induced immune response, though ASFV-specific p72 antibodies were absent. The cocktail did not cause cytokine imbalance, indicating the vector's safety in pigs. Despite some delay in disease progression, the protection against genotype II ASFV was inadequate, underscoring the need to select more effective antigens and enhance immune responses for virus-vectored vaccines.