Major Immunodominant Region of Hepatitis B Virus Core Antigen as a Delivery Vector to Improve the Immunogenicity of the Fusion Antigen ROP2-SAG1 Multiepitope from Toxoplasma gondii in Mice.

To prepare the dominant multiepitope fusion antigen ROP2-SAG1 (RSmultiepitope) from Toxoplasma gondii in a prokaryotic system, the major immunodominant region (MIR) of the human hepatitis B virus core antigen (HBcAg(MIR)) was used as a delivery vector. The gene encoding the RSmultiepitope was inserted into HBcAg(MIR), and rHBcAg(MIR)-RSmultiepitope was prepared, purified, and administered to BALB/c mice through intradermal injection. An indirect enzyme-linked immunosorbent assay analysis based on a multiepitope peptide facilitated the specific differentiation of sera obtained from mice immunized with the rHBcAg(MIR)-RSmultiepitope protein, and high titers (greater than 1:6,400) of specific anti-RSmultiepitope antibodies were obtained. Immunized splenocytes demonstrated enhanced IFN-γ production. Based on these results, the HBcAg(MIR) vector is easily applied in vitro for targeting the RSmultiepitope and efficiently presents this target epitope for the induction of significant humoral and cellular immune responses. This study offers a novel strategy for the design of a target epitope delivery system for a toxoplasmosis vaccine.