In vivo immunogenicity assessment of a multiepitope‐displayed phage vaccine against Brucella species infection in BALB/c mice

Abstract

Bacteriophages are considered ideal vaccine platforms owing to their safety, intrinsic adjuvant properties, stability, and low‐cost production. One of the best strategies to prevent brucellosis in humans and animals is vaccination. For several years, researchers have dedicated their efforts to enhance the effectiveness and safety of the Brucella vaccine. This study was designed to evaluate the immunogenicity of a phage vaccine displaying multiepitopes from six different Brucella protective proteins in a mouse model. This study used immunoinformatics to predict T‐ and B‐cell epitopes. Subsequently, a multiepitope protein was synthesized and recombinant phages displaying the multiepitope protein were prepared. The multiepitope protein display on the phage was confirmed by Western blot analysis. Six groups of BALB/c mice (6 mice per group) received multiepitope phage (as a vaccine), helper phage, and PBS as controls subcutaneously or orally. An ELISA assay was used to analyze the humoral response in mouse serum, while an interferon‐gamma ELISpot assay was performed on mouse splenocytes to evaluate the cell‐mediated immune response. Mice immunized with multiepitope phage showed significant serum levels of specific IgG and significant numbers of specific IFN‐producing T cells in splenic lymphocytes (p‐value <0.05). The oral administration route provided a much stronger cellular response than a subcutaneous injection (about 10‐fold), which is important for combating brucellosis infection. These findings provide the first evidence that a multiepitope‐displayed phage vaccine may be a promising avenue for developing a safe and efficient vaccine against Brucella species.