Evaluation of the Immunogenicity of a Pool of Recombinant Lactococcus lactis Expressing Eight Antigens of African Swine Fever Virus in a Mouse Model.

African swine fever (ASF), caused by African swine fever virus (ASFV), poses a great threat to the global pig industry. There is an urgent demand for effective and safe vaccines to address this threat. This study reports the generation and evaluation of a recombinant Lactococcus lactis pool, each strain expressing one of eight ASFV antigens (F317L, H171R, D117L, E120R, B602L, CD2v, p54, and p72). We evaluated the immune responses in mice through oral gavage and intramuscular immunization to the recombinant L. lactis pool. The results show that the mice immunized via intramuscular injection induced high-level serum IgG antibodies within 7 d post-primary immunization, which was maintained over an extended period. Additionally, there was a marked increase in the interferon gamma (IFN-γ) and interleukin 10 (IL-10) levels in the sera. In contrast, the mice immunized via oral gavage did not induce obvious serum IgG antibodies. However, they experienced a transient peak of secretory IgA (sIgA) antibodies in fecal samples within 7 d post-primary immunization, which subsequently decreased to levels that were statistically similar to those in the control group. In addition, this study also found that the multi-antigen cocktail vaccination was safe for mice. This study provides a reference for the development and immunization of ASF vaccines with L. lactis as live carriers.