title: Plasmids enriched with CpG motifs activate human peripheral blood mononuclear cells in vitro and enhance th-1 immune responses to hepatitis B surface antigen in mice.
abstract: T helper-1 (Th-1)-type immune responses play an important role in viral clearance during infection with hepatitis B virus (HBV). Unmethylated CpG motifs present in bacterial DNA can activate toll-like receptor 9 (TLR9) signals and act as potent adjuvants to induce Th-1-type immune responses. Here, a mini-plasmid with 812 base pairs in length was constructed and used as a vector to prepare a series of plasmids containing 3-21 copies of D-type CpG motifs. In vitro, these CpG-enriched plasmids strongly stimulated proliferation of human peripheral blood mononuclear cells (PBMCs) and enhanced secretion of interferon-γ (IFN-γ) and interleukin-12 (IL-12). The responses of the PBMCs from healthy individuals to the plasmids were stronger than those obtained from HBV-infected individuals. Contrary to the strong Th-2-biased response induced by surface antigen of hepatitis B virus (HBsAg) plus alum adjuvant, immunization of BALB/c mice with HBsAg plus these plasmids induced a strong Th-1-biased response. The plasmids increased the titers of HBsAg-specific total immunoglobulin G (IgG) and IgG(2a). HBsAg-specific IL-2 and IFN-γ production and cytotoxic activity were also enhanced in the presence of the plasmids. The strength of the immune responses positively correlated with the number of CpG motifs in the plasmids. These results indicate that the use of CpG-enriched plasmids as an adjuvant to recombinant HBsAg could provide a promising and cost-effective approach for the development of efficacious therapeutic vaccines against HBV infection.
authors.affiliation: Department of Infectious Diseases, Affiliated Changhai Hospital, Second Military Medical University, Shanghai, China.
authors.forename: Zhihui
authors.initials: Z
authors.lastname: Chen
authors.forename: Jie
authors.initials: J
authors.lastname: Cao
authors.forename: Xiaoling
authors.initials: X
authors.lastname: Liao
authors.forename: Jinshan
authors.initials: J
authors.lastname: Ke
authors.forename: Shiying
authors.initials: S
authors.lastname: Zhu
authors.forename: Ping
authors.initials: P
authors.lastname: Zhao
authors.forename: Zhongtian
authors.initials: Z
authors.lastname: Qi
mesh_terms: D000328:Adult; D000818:Animals; D049109:Cell Proliferation; D002478:Cells, Cultured; D018899:CpG Islands / Q000276:immunology*; D005260:Female; D006510:Hepatitis B Antibodies / Q000097:blood; D006514:Hepatitis B Surface Antigens / Q000276:immunology*; D017325:Hepatitis B Vaccines / Q000276:immunology*; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood; D007371:Interferon-gamma / Q000378:metabolism; D018664:Interleukin-12 / Q000378:metabolism; D007963:Leukocytes, Mononuclear / Q000276:immunology*; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D010957:Plasmids / Q000276:immunology*; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology; D018417:Th1 Cells / Q000276:immunology*; D019444:Vaccines, DNA / Q000276:immunology*
chemical_list: D006510:Hepatitis B Antibodies; D006514:Hepatitis B Surface Antigens; D017325:Hepatitis B Vaccines; D007074:Immunoglobulin G; D019444:Vaccines, DNA; D018664:Interleukin-12; D007371:Interferon-gamma