Clostridium perfringens is one of the main causes of death in poultry with no vaccines approved for poultry at present. The appropriate adjuvant is critical for the development of vaccines in C. perfringens in poultry. Here, we utilized Levilactobacillus brevis for high-yielding selenium biotransformation and demonstrated that heat-inactivated nano-selenium Lactobacillus (HiSeL) is a safe, efficient, and chemically stable selenium immunopotentiator for C. perfringens vaccines. We evaluated the effectiveness of HiSeL as an immune adjuvant to modulate the efficacy of multi-epitope vaccine in mice. Subcutaneous immunization mice with HiSeL promoted high levels of specific IgG, modulated cytokine secretion, downregulated stress-related gene expression, and provided 100% protection against lethal challenge with C. perfringens. Surprisingly, we found that HiSeL can quickly and effectively induce SIgA production even by subcutaneous immunization. Transcriptome sequencing revealed the pivotal role of TGF-β and NF-κB signaling pathways in IgA immune responses in mice immunized with the HiSeL-adjuvanted multi-epitope vaccine. Collectively, our study provides proof-of-concept evidence that HiSeL functions as a potent adjuvant candidate for the multi-epitope vaccine in a murine model, offering new insights into the development of engineered postbiotic-based adjuvants.

Keywords: adjuvant; mucosal IgA; multi-epitope vaccine; nano selenium; probiotics.