title: The Fusion Protein of CTP-HBcAg18-27-Tapasin Mediates the Apoptosis of CD8(+)T Cells and CD8(+) T Cell Response in HLA-A2 Transgenic Mice.
abstract: BACKGROUND
  HBV-specific cytotoxic T lymphocyte (CTL) activity is believed to play a critical role in controlling HBV infection. The phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway manipulates cell fate decisions in many different cell types by regulating the activity of downstream effectors. We have previously testified that the fusion protein of CTP-HBcAg18-27--Tapasin could enter the cytoplasm of dendritic cells and efficiently induce robust specific CTL response in vitro.
  
  
  OBJECTIVE
  In the present study, we evaluated specific CTL response and the level of apoptosis of CD8+ T cells induced by CTP-HBcAg18-27-Tapasin in HLA-A2 transgenic mice (H-2Kb). Meanwhile, we preliminary investigated PI3K, phosphorylation level of Akt, and mammalian target of rapamycin (mTOR) as positive regulator of the magnitude and effector function of the hepatitis B virus-specific cytotoxic T lymphocytes in HLA-A2 transgenic mice.
  
  
  METHODS
  HLA-A2 transgenic mice were immunized by intramuscular injection in the hind legs three times at one-week intervals with PBS, CTP-HBcAg18-27-Tapasin (50 μg), CTP-HBcAg18-27 (50 μg), HBcAg18-27-Tapasin (50 μg), and HBcAg18-27 (50 μg). One week after the last immunization, mice were sacrificed and splenocytes were harvested in strile condition. The specific CTL response was analyzed by flow cytometry and enzyme linked immunosorbent assay (ELISA); the expression of (PI3K)/Akt signaling was detected by RT-PCR and western blot.
  
  
  RESULTS
  The results showed that CTP-HBcAg18-27-Tapasin significantly increased the percentages of IFN-γ(+) CD8α(+) T cells, the numbers of these polyfunctional triple-cytokine-producing (IFN-γ, TNF-α, and IL-2) CD8(+)T cells, the secretion of cytokine IFN-γ, IL-2, and TNF-α, while in comparison to control group, it significantly decreased the percentage of apoptotic CD8(+) T cells in HLA-A2 transgenic mice. Moreover, the expression of PI3K, P-Akt, and P-mTOR was significantly upregulated in CTP-HBcAg18-27-Tapasin group compared with control groups.
  
  
  CONCLUSIONS
  In conclusion, CTP-HBcAg18-27-Tapasin could reduce apoptosis of CD8(+) T cells, increase the percentages of IFN-γ(+) CD8α(+) T cells, and elicit cell-mediated immunity in HLA-A2 transgenic mice; these processes were associated with activation of the PI3K/Akt signaling pathway.
authors.affiliation: Department of Infectious Disease, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai, China.
authors.forename: Yu-Yan
authors.initials: YY
authors.lastname: Tang
authors.affiliation: Department of Infectious Disease, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai, China.
authors.forename: Zheng-Hao
authors.initials: ZH
authors.lastname: Tang
authors.affiliation: Department of Infectious Disease, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai, China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Department of Infectious Disease, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai, China.
authors.forename: Meng
authors.initials: M
authors.lastname: Zhuo
authors.affiliation: Department of Infectious Disease, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai, China.
authors.forename: Guo-Qing
authors.initials: GQ
authors.lastname: Zang
authors.affiliation: Department of Infectious Disease, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai, China.
authors.forename: Xiao-Hua
authors.initials: XH
authors.lastname: Chen
authors.affiliation: Department of Infectious Disease, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai, China.
authors.forename: Yong-Sheng
authors.initials: YS
authors.lastname: Yu
keywords: Mice, Transgenic; PI3K/Akt; T-Lymphocytes, Cytotoxic; Tapasin