title: DNA immunization with fusion of CTLA-4 to hepatitis B virus (HBV) core protein enhanced Th2 type responses and cleared HBV with an accelerated kinetic.
abstract: BACKGROUND
  Typically, DNA immunization via the intramuscular route induces specific, Th1-dominant immune responses. However, plasmids expressing viral proteins fused to cytotoxic T lymphocyte antigen 4 (CTLA-4) primed Th2-biased responses and were able to induced effective protection against viral challenge in the woodchuck model. Thus, we addressed the question in the mouse model how the Th1/Th2 bias of primed immune responses by a DNA vaccine influences hepatitis B virus (HBV) clearance.
  
  
  RESULTS
  Plasmids expressing HBV core protein (HBcAg) or HBV e antigen and HBcAg fused to the extracellular domain of CTLA-4 (pCTLA-4-HBc), CD27, and full length CD40L were constructed. Immunizations of these DNA plasmids induced HBcAg-specific antibody and cytotoxic T-cell responses in mice, but with different characteristics regarding the titers and subtypes of specific antibodies and intensity of T-cell responses. The plasmid pHBc expressing HBcAg induced an IgG2a-dominant response while immunizations of pCTLA-4-HBc induced a balanced IgG1/IgG2a response. To assess the protective values of the immune responses of different characteristics, mice were pre-immunized with pCTLA-4-HBc and pHBc, and challenged by hydrodynamic injection (HI) of pAAV/HBV1.2. HBV surface antigen (HBsAg) and DNA in peripheral blood and HBcAg in liver tissue were cleared with significantly accelerated kinetics in both groups. The clearance of HBsAg was completed within 16 days in immunized mice while more than 50% of the control mice are still positive for HBsAg on day 22. Stronger HBcAg-specific T-cell responses were primed by pHBc correlating with a more rapid decline of HBcAg expression in liver tissue, while anti-HBs antibody response developed rapidly in the mice immunized with pCTLA-4-HBc, indicating that the Th1/Th2 bias of vaccine-primed immune responses influences the mode of viral clearance.
  
  
  CONCLUSIONS
  Viral clearance could be efficiently achieved by Th1/Th2-balanced immune response, with a small but significant shift in T-cell and B-cell immune responses.
authors.affiliation: Department of Microbiology, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Yin
authors.forename: Chunchen
authors.initials: C
authors.lastname: Wu
authors.forename: Jingjiao
authors.initials: J
authors.lastname: Song
authors.forename: Junzhong
authors.initials: J
authors.lastname: Wang
authors.forename: Ejuan
authors.initials: E
authors.lastname: Zhang
authors.forename: Hongyan
authors.initials: H
authors.lastname: Liu
authors.forename: Dongliang
authors.initials: D
authors.lastname: Yang
authors.forename: Xinwen
authors.initials: X
authors.lastname: Chen
authors.forename: Mengji
authors.initials: M
authors.lastname: Lu
authors.forename: Yang
authors.initials: Y
authors.lastname: Xu
mesh_terms: D000818:Animals; D000918:Antibody Specificity; D019677:Artificial Gene Fusion; D001402:B-Lymphocytes / Q000276:immunology / Q000821:virology; D023201:CD40 Ligand / Q000235:genetics / Q000276:immunology; D060908:CTLA-4 Antigen / Q000235:genetics*; D004279:DNA, Viral / Q000008:administration & dosage / Q000493:pharmacokinetics; D000939:Epitopes / Q000276:immunology; D005260:Female; D006512:Hepatitis B Core Antigens / Q000235:genetics* / Q000276:immunology; D006513:Hepatitis B e Antigens / Q000235:genetics / Q000276:immunology; D006515:Hepatitis B virus / Q000276:immunology* / Q000378:metabolism; D007114:Immunization / Q000379:methods*; D007074:Immunoglobulin G / Q000276:immunology; D008099:Liver / Q000276:immunology / Q000378:metabolism / Q000821:virology; D008392:Marmota; D008657:Metabolic Clearance Rate; D051379:Mice; D010957:Plasmids / Q000235:genetics; D018417:Th1 Cells / Q000276:immunology / Q000821:virology; D018418:Th2 Cells / Q000276:immunology*; D018127:Tumor Necrosis Factor Receptor Superfamily, Member 7 / Q000235:genetics / Q000276:immunology; D019444:Vaccines, DNA / Q000235:genetics / Q000276:immunology*; D014765:Viral Vaccines / Q000235:genetics / Q000276:immunology
chemical_list: D060908:CTLA-4 Antigen; D004279:DNA, Viral; D000939:Epitopes; D006512:Hepatitis B Core Antigens; D006513:Hepatitis B e Antigens; D007074:Immunoglobulin G; D018127:Tumor Necrosis Factor Receptor Superfamily, Member 7; D019444:Vaccines, DNA; D014765:Viral Vaccines; D023201:CD40 Ligand