Preclinical safety evaluation of DNA vaccines encoding modified HPV16 E6 and E7

Area of Science:

• Oncology
• Immunology
• Virology

Background:

• Persistent high-risk human papillomavirus (hrHPV) infections are linked to anogenital cancers.
• HPV oncoproteins E6 and E7 are crucial for cancer development, making them targets for immunotherapy.
• Previous work developed DNA vaccines encoding gene-shuffled HPV16 E6 and E7 fused to Tetanus Toxin Fragment C (TTFC) to induce T cell immunity.

Purpose of the Study:

• To assess the preclinical safety of TTFC-E6SH and TTFC-E7SH DNA vaccines.
• To evaluate the transforming capacity of gene-shuffled HPV16 E6 and E7 proteins in vitro.
• To determine the suitability of these candidate vaccines for clinical trials.

Main Methods:

• In vitro transformation assays using murine fibroblasts (NIH 3T3 cells).
• In vitro transformation assays using primary human foreskin keratinocytes (HFKs) from multiple donors.
• Analysis of colony formation in soft agar and cell immortalization following gene expression.

Main Results:

• Neither TTFC-E6SH nor TTFC-E7SH, alone or combined, induced NIH 3T3 cell transformation or soft agar colony formation.
• Wild-type HPV16 E6 and E7 (E6WT and E7WT) effectively transformed NIH 3T3 cells.
• TTFC-E6SH and TTFC-E7SH did not immortalize HFKs, whereas E6WT and E7WT did.

Conclusions:

• The gene-shuffled HPV16 E6 and E7 vaccine constructs (TTFC-E6SH and TTFC-E7SH) demonstrate a favorable safety profile.
• The absence of transforming activity supports the advancement of these DNA vaccines into clinical evaluation.
• These vaccines represent a promising immunotherapeutic strategy for HPV16-associated malignancies.