[Epitopic multiple antigen peptide from α-fetoprotein elicit antitumor immune response in vitro and ex vivo].
OBJECTIVE
To explore the antitumor effects of multiple antigen peptide (MAP) vaccine from α-fetoprotein (AFP) through AFP-specific cytotoxic T lymphocyte (CTL) against hepatoma in vitro and ex vivo.


METHODS
Dendritic cells (DC) were generated from human peripheral blood mononuclear cells (PBMC) and HLA-A2.1-transgenic murine bone marrow. The AFP-specific CTL were induced by MAP-loaded DC and the corresponding linear peptides from human AFP. The lysis rate of effectors to hepatoma cells were tested by 4 h (51)Cr release assay. And enzyme-linked immunosorbent spot (ELISPOT) was used to test the interferon (IFN)-γ release of effector cells.


RESULTS
The specific lysis rate of effectors induced by AFP epitopic MAP vaccines to Hep3B cells (AFP(+), HLA-A2.1(+)) at the highest effector/target (E/T) ratio was significantly higher than linear peptide vaccine (73.5% ± 7.9% vs 45.6% ± 6.9%, P < 0.01). The effectors induced by AFP epitopic MAP vaccine and linear peptide vaccine could not lysis the AFP-negative PLC/PRF/5 liver cancer cells versus the negative control group at the highest E/T (9.3% ± 3.9%, 8.1% ± 2.8% vs 8.3% ± 2.6%, both P > 0.05). But the effectors induced by AFP epitopic MAP vaccine and linear peptide vaccine could lyse PLC/PRF/5 liver cancer cells transfected with cDNA of AFP versus the negative control group (74.8% ± 10.5%, 51.4% ± 12.6% vs 4.2% ± 1.3%, both P < 0.01). And the specific lysis rate of effectors induced by AFP epitopic MAP vaccines was significantly higher than the corresponding linear peptide vaccine (P < 0.01). Compared with the negative control group, the effectors could not lyse HepG2 liver cancer cells, a HLA-A2.1 negative cell line (both P > 0.05). But the effectors could lyse HepG2 cells transfected with cDNA of HLA-A2.1 (71.8% ± 8.6%, 46.5% ± 6.5% vs 4.1% ± 1.1%, both P < 0.01). And the specific lysis rate of effectors induced by MAP vaccine was significantly higher than the corresponding linear peptide vaccine (P < 0.01). ELISPOT test showed that the capability of enhancing IFN-γ release of human AFP MAPs was stronger than that of the AFP linear peptides. The spots count of MAP vaccine group ((158 ± 23) spots/10(5) cells) or linear peptide vaccine group ((78 ± 12) spots/10(5) cells) were significantly higher than the negative control group ((3 ± 1) spots/10(5) cells) (all P < 0.01). The spots count of the positive control group ((166 ± 32) spots/10(5) cells) showed no significant difference with the AFP MAP vaccine group (P > 0.05). And the spots count of MAP vaccine group were significantly higher than the corresponding linear peptide vaccine group ((78 ± 12) spots/10(5) cells, P < 0.01).


CONCLUSIONS
AFP multiple antigen peptides elicit not only more powerful specific anti-tumor immune responses but also stronger non-specific anti-tumor immune activities than their corresponding linear peptides. These findings will provide theoretical rationales for their clinical applications.
Department of Gastroenterology, Kunming General Hospital of Chengdu Military Command, Kunming 650032, China.
Zong-jiang
ZJ
Fan
Shu-rong
SR
Zhang
D000818:Animals; D019496:Cancer Vaccines / Q000276:immunology*; D056945:Hep G2 Cells; D006801:Humans; D008113:Liver Neoplasms / Q000276:immunology* / Q000517:prevention & control; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D010446:Peptide Fragments / Q000276:immunology; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology; D000509:alpha-Fetoproteins / Q000276:immunology*
D019496:Cancer Vaccines; D010446:Peptide Fragments; D000509:alpha-Fetoproteins