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Cryptic open reading frames in plasmid vector backbone sequences can provide highly immunogenic cytotoxic
T van Hall1, N E van de Rhee, S P Schoenberger
1Department of Immunohematology and Blood Bank, Leiden University Medical Center, The Netherlands.
Cancer Research
|July 29, 1998
Summary
Researchers discovered a new, highly immunogenic peptide in tumor cells, originating from plasmid DNA backbones. This finding is crucial for interpreting preclinical experiments and designing effective DNA vaccines against cancer.
Area of Science:
- Immunology
- Molecular Biology
- Oncology
Background:
- Transfected murine tumor cells expressing oncogenes are vital for cancer immunology research.
- Cells transformed with mutated p53 or human papilloma virus type 16 (HPV16) present specific MHC-bound peptides, enabling antitumor T-cell responses.
Purpose of the Study:
- To identify an additional, highly immunodominant peptide presented by HPV16- and p53-transformed murine tumor cells.
- To investigate the origin and expression mechanism of this novel peptide epitope.
Main Methods:
- Molecular cloning was employed to identify the immunodominant peptide.
- Transcriptional analysis was performed to detect transcripts from cryptic open reading frames in plasmid backbone sequences.
- Analysis of tumor cells transfected with different expression plasmids (LTR-driven vs. unidirectional promoters).
- Assessment of CTL response in mice vaccinated with LTR-driven DNA plasmids.
Main Results:
- An additional, highly immunodominant peptide was identified, encoded by a cryptic open reading frame within the plasmid backbone.
- This peptide results from bidirectional transcription driven by the retroviral long terminal repeat (LTR) in expression plasmids.
- LTR-driven plasmids led to higher expression of the immunogenic peptide in tumor cells compared to unidirectional promoters.
- DNA vaccination with LTR-driven plasmids induced a CTL response against the identified peptide.
Conclusions:
- Plasmid backbone sequences can encode highly immunogenic peptides, impacting preclinical research.
- Understanding these plasmid backbone-derived epitopes is essential for accurate interpretation of experimental data.
- This knowledge is critical for the rational design of effective DNA vaccines.