Oral ASFV Vaccine Using *Bacillus subtilis* Spores Markedly Boosts Rat Humoral and Cellular Immunity

The African Swine Fever Virus (ASFV) causes a highly fatal hemorrhagic disease in domestic pigs and wild boars, posing a severe global threat to the pork industry. Current live attenuated vaccines (LAVs) for ASFV, while promising, often exhibit a narrow margin between efficacy and residual virulence, raising significant safety concerns. This critical gap necessitates the development of novel, safe, and effective vaccine strategies, particularly those that can be administered orally for widespread deployment and ease of use in large populations, moving beyond the limitations of traditional injectable vaccines.

Researchers constructed an oral vaccine by genetically engineering Bacillus subtilis spores to display ASFV fusion antigens on their surface. Recombinant strains capable of stable antigen expression were developed. Rats were then subjected to oral immunization with these recombinant spores. The study evaluated the immune response by measuring the spleen index and the levels of ASFV-specific IgG, interleukin-2 (IL-2), and interferon-γ (IFN-γ) to assess both humoral and cellular immunity. A control arm, though not explicitly detailed, is implied by the comparative nature of immune response measurements.

Oral immunization with the recombinant Bacillus subtilis spores successfully displaying ASFV fusion antigens elicited a robust immune response in rats. The study observed a marked increase in the spleen index, indicating a significant immune cell proliferation. Furthermore, the levels of ASFV-specific IgG were markedly increased, demonstrating a strong humoral immune activation. Crucially, the cellular immune response was also effectively activated, evidenced by markedly increased levels of interleukin-2 (IL-2) and interferon-γ (IFN-γ). These cytokines are critical mediators of T-cell responses and antiviral immunity. The findings collectively indicate that the constructed spore-based vaccine system triggered favorable and comprehensive immune responses in vivo.