Chimeric hepatitis B virus core particles displaying Neisserial surface protein A confer protection against virulent Neisseria meningitidis serogroup B in BALB/c mice

Abstract

Purpose

The primary goal of the present study was to explore and evaluate the highly conserved Neisserial surface protein A (NspA) molecule, fused with truncated HBV virus-like particles (VLPs), as a candidate vaccine against the virulent Neisseria meningitidis serogroup B (NMB).

Methods

NspA was inserted into the major immunodominant region of the truncated hepatitis B virus core protein (HBc; amino acids 1–144). The chimeric protein, HBc-N144-NspA, was expressed from a prokaryotic vector and generated HBc-like particles, as determined by transmission electron microscopy. Further, the chimeric protein and control proteins were used to immunize mice and the resulting immune responses evaluated by flow cytometry, enzyme-linked immunosorbent assay, and analysis of serum bactericidal activity (SBA) titer.

Results

Evaluation of the immunogenicity of the recombinant HBc-N144-NspA protein showed that it elicited the production of high levels of NspA-specific total IgG. The SBA titer of HBc-N144-NspA/F reached 1:16 2 weeks after the last immunization in BALB/c mice, when human serum complement was included in the vaccine. Immunization of HBc-N144-NspA, even without adjuvant, induced high levels of IL-4 and a high IgG1 to IgG2a ratio, confirming induction of an intense Th2 immune response. Levels of IL-17A increased rapidly in mice after the first immunization with HBc-N144-NspA, indicating the potential for this vaccine to induce a mucosal immune response. Meanwhile, the immunization of HBc-N144-NspA without adjuvant induced only mild inflammatory infiltration into the mouse muscle tissue.

Conclusion

This study demonstrates that modification using HBc renders NspA a candidate vaccine, which can trigger protective immunity against NMB.

Keywords:

• hepatitis B core protein
• Neisserial surface protein A
• virus-like particles
• recombinant protein vaccine
• Neisseria meningitidis serogroup B

Supplementary material

Figure S1 Analysis of the recombinant proteins HBc-N144, rNspA,HBc-N144-NspA by SDS-PAGE.

Notes: Lane M: protein molecular weight marker in KDa; (A) Lane 1: uninduced bacteria expressing HBc-N144; Lane 2: induced bacteria expressing HBc-N144; Lane 3: purified HBc-N144; (B) Lane 1: induced bacteria supernatant expressing HBc-N144-NspA; Lane 2: induced bacteria sediment expressing HBc-N144-NspA; Lane 3–5: purified HBc-N144-NspA with serial concentration of elution buffer. (C) Lane 1–5: purified rNspA.

Abbreviations: HBc-N144, N terminal 144 amino acids of hepatitis B core protein; HBc-N144-NspA, Neisserial surface protein A fuzed with the N terminal 144 amino acids of hepatitis B core protein; rNspA, Neisserial surface protein A.

Acknowledgments

This work was supported by the National Natural Science Foundation of China under grant 81172890, by the Hunan Provincial Key Laboratory for Special Pathogens Prevention, and by the Hunan Province Cooperative Innovation Center for Molecular Target New Drug Study (2015-351). The authors thank Mr. Ting Yan (Air Force Medical University) for his excellent technical assistance and advice.

Disclosure

The authors report no conflicts of interest in this work.