Expression Purification and Immunogenicity Detection of HtsA + FtsB Fusion Protein From <i>Streptococcus pyogenes</i>

Lipoproteins are a class of potential vaccine candidates for Streptococcus pyogenes. The present study was conducted to purify and detect the immunogenicity of the fusion protein HtsA + FtsB of the iron transport lipoproteins HtsA and FtsB of S. pyogenes. The recombinant expression vector pBAD-htsA + ftsB was successfully constructed, and the fusion protein HtsA + FtsB with a purity above 95% was successfully obtained. Western blot analysis confirmed that the HtsA + FtsB fusion protein had good antigenicity and could be specifically recognized by both HtsA antiserum and FtsB antisera, and the antibody specificity of the HtsA + FtsB fusion protein was good. ELISA results showed that IgG antibody levels were significantly increased in the HtsA + FtsB fusion protein immunization group compared to the PBS control group. Additionally, cytokine levels, including IL-2, IFN-γ, IL-4, IL-6, and IL-17A, were significantly elevated. Furthermore, the antiserum from HtsA + FtsB-immunized mice enhanced the opsonophagocytic activity against S. pyogenes. The HtsA + FtsB fusion protein has strong immunogenicity and potential as a candidate vaccine for S. pyogenes.