Signal sequence deletion and fusion to tetanus toxoid epitope augment antitumor immune responses to a human carcinoembryonic antigen (CEA) plasmid DNA vaccine in a murine test system.
Carcinoembryonic antigen (CEA, CEACAM5) is expressed on several human carcinomas including colon cancer. CEA contains signal peptides that target the protein through the endoplasmic reticulum and to the cell membrane. We constructed a plasmid DNA vaccine encoding a truncated CEA (deltaCEA), devoid of its signal peptides, and demonstrated that it was retained inside the cell, while full-length CEA (wtCEA) was expressed on the membrane. We hypothesized that intracellular retention of deltaCEA would enhance MHC class I presentation of CEA peptides, thus favoring cellular immune responses. In addition, a promiscuous T-helper epitope (Q830-L844 of tetanus toxoid) was fused to the N-terminal of the truncated CEA gene (tetdeltaCEA). C57BL/6 mice immunized with DNA encoding wtCEA or tetdeltaCEA developed both humoral and cellular immune responses to CEA. SCID mice transplanted with spleen cells from tetdeltaCEA but not wtCEA-immunized C57BL/6 mice showed strong suppression of tumor growth after inoculation of human CEA-expressing colon carcinoma cells. Immune spleen cell populations depleted for either B, T or both B and T cells were active, indicating that effector cells might also reside in other populations. The present approach to manipulating antigen presentation may open new possibilities for immunotherapy against colon and other CEA-secreting carcinomas.
Karolinska Institutet, Microbiology and Tumor Biology Center, Box 280, SE-171 77 Stockholm, Sweden.
Lars H
LH
Lund
Karolina
K
Andersson
Bartek
B
Zuber
Anneli
A
Karlsson
Gunnel
G
Engström
Jorma
J
Hinkula
Britta
B
Wahren
Gösta
G
Winberg
D000818:Animals; D019677:Artificial Gene Fusion; D001402:B-Lymphocytes / Q000276:immunology; D002272:Carcinoembryonic Antigen / Q000276:immunology*; D002455:Cell Division; D003110:Colonic Neoplasms / Q000276:immunology / Q000517:prevention & control*; D018014:Gene Transfer Techniques; D005822:Genetic Vectors; D006801:Humans; D007114:Immunization; D051379:Mice; D008810:Mice, Inbred C57BL; D016513:Mice, SCID; D010446:Peptide Fragments; D010957:Plasmids / Q000235:genetics; D021382:Protein Sorting Signals; D017384:Sequence Deletion; D013154:Spleen / Q000276:immunology; D015996:Survival Rate; D013601:T-Lymphocytes / Q000276:immunology; D013745:Tetanus Toxoid / Q000235:genetics*; D019444:Vaccines, DNA / Q000008:administration & dosage*
D002272:Carcinoembryonic Antigen; D010446:Peptide Fragments; D021382:Protein Sorting Signals; D013745:Tetanus Toxoid; D019444:Vaccines, DNA