Enhancement of humoral immune responses to HBsAg by heat shock protein gp96 and its N-terminal fragment in mice.
OBJECTIVE
Most studies on the immune effect of gp96 were focused on its enhancement of CTLs. It is interesting to know whether gp96 could influence the humoral immune response, and whether the recombinant N-terminal fragment of gp96 could substitute native gp96 to stimulate the immune system.


METHODS
gp96 isolated from livers of normal mice and its N-terminal fragment (amino acid 22-355) expressed in E coli were used for immunization of BALb/c mice. Eight groups of mice received one of the following regiments subcutaneously in 100 microL phosphate buffered saline (PBS) at an interval of 3 wk. Group 1: PBS only; group 2: gp96 only; group 3: N-terminal fragment only; group 4: HBsAg only; group 5: HBsAg+gp96; group 6: HBsAg+N-terminal fragment; group 7: HBsAg+incomplete Freud's adjuvant; group 8: HBsAg+N-terminal fragment (95 degrees heated for 30 min). Serum anti-HBsAg antibody levels were assayed by ELISA. CTL responses in splenocytes were analyzed by ELISPOT after the last vaccination.


RESULTS
The average titer of serum anti-HBsAg antibody in the mice immunized with HBsAg together with gp96 or its N-terminal fragment were much higher than those immunized with HBsAg alone detected by ELISA. The cellular immune response of the mice immunized with HBsAg together with gp96 or its N-terminal fragment was not different with those immunized with HBsAg alone measured by ELISPOT assay.


CONCLUSIONS
gp96 or its N-terminal fragment greatly improved humoral immune response induced by HBsAg, but failed to enhance the CTL response, which demonstrated the potential of using gp96 or its N-terminal fragment as a possible adjuvant to augment humoral immune response against HBV infection.
Li
Hong-Tao
HT
Department of Molecular Virology, Institute of Microbiology, Chinese Academy of Sciences, Zhongguancun Beiyitiao, Beijing 100080, China.
Yan
Jia-Bin
JB
Li
Jing
J
Zhou
Ming-Hai
MH
Zhu
Xiao-Dong
XD
Zhang
Yu-Xia
YX
Tien
Po
P
D000818:Animals; D000951:Antigens, Neoplasm / Q000276:immunology* / Q000302:isolation & purification; D005260:Female; D006509:Hepatitis B / Q000276:immunology / Q000517:prevention & control*; D006514:Hepatitis B Surface Antigens / Q000276:immunology*; D017325:Hepatitis B Vaccines / Q000276:immunology*; D008099:Liver; D051379:Mice; D008807:Mice, Inbred BALB C; D010446:Peptide Fragments / Q000276:immunology / Q000302:isolation & purification
D000951:Antigens, Neoplasm; D006514:Hepatitis B Surface Antigens; D017325:Hepatitis B Vaccines; D010446:Peptide Fragments; C052646:sarcoma glycoprotein gp96 rejection antigens