Efficient direct priming of tumor-specific cytotoxic T lymphocyte in vivo by an engineered APC

• Published in: Cancer research (Chicago, Ill.) Ill.), 1998-07, Vol.58 (14), p.3094-3100
• Main Authors: SCHOENBERGER, S. P, JONGES, L. E, MOOIJAART, R. J. D, HARTGERS, F, TOES, R. E. M, KAST, W. M, MELIEF, C. J. M, OFFRINGA, R
• Format: Article
• Language: English
• Subjects: Adenovirus E1A Proteins - immunology; Animals; Antigen-Presenting Cells - immunology; Antineoplastic agents; B7-1 Antigen - immunology; Biological and medical sciences; CD4-Positive T-Lymphocytes - immunology; Female; Immunotherapy; Male; Medical sciences; Mice; Mice, Inbred BALB C; Mice, Inbred C57BL; Mice, SCID; Pharmacology. Drug treatments; T-Lymphocytes, Cytotoxic - immunology
• ISSN: 0008-5472; 1538-7445

Although numerous studies have documented a role for B7-1 (CD80) in the induction of antitumor CTL immunity, it is presently unclear to what extent expression of this costimulatory molecule truly endows tumors with significant in vivo APC (antigen-presenting cell) capacity. Recent studies have, in fact, demonstrated that cross-priming, rather than direct priming, may constitute the major mechanism of CTL induction by B7-1 expressing tumors. We have, therefore, investigated the requirements for antigen density and costimulatory molecules in direct CTL priming with a prototype cell-based vaccine that uses a signal sequence-containing minigene to direct expression of a tumor-specific CTL epitope to the endoplasmic reticulum. This design limits sources of antigen available to professional APC in the host and, thereby, the contribution of cross-priming. Induction of antitumor CTL immunity by our prototype APC was shown to solely involve direct priming, independent of host APC, NKI.1+ cells, and CD4+ T cell help. CTL induction through this mechanism required the engineered APC to express the B7-1 molecule as well as a sufficiently high density of peptide/MHC complexes at its surface. Our data, in contrast to previous studies using modified tumor cells, clearly define the antigenic and costimulatory requirements for a suitably engineered "artificial" APC to directly prime peptide-specific CTL in vivo, and demonstrate that the signal sequence minigene approach allows the engineering of highly effective and well-defined cellular vaccines for activation of CTL against epitopes of choice.