1135 A novel self-assembling vaccine, VTX-067, targeting E6/E7 proteins of human papilloma virus induces T cell immune responses and inhibits HPV E6/E7 expressing tumor growth in a C57/B6 mouse model

Background Human papillomavirus (HPV) infection is associated with skin and mucosal papillomas or warts and cervical, anal and head and neck cancer. We developed a novel, broadly immune activating, self-assembling vaccine (SAV)1 which consists of a Mycobacterium tuberculosis heat shock protein 70 (MtbHSP70)-avidin (MAV) as an adjuvant that spontaneously self-assembles with biotinylated immunogenic peptides targeting the E6 and E7 proteins of HPV (VTX-067). Methods Two biotinylated concatemerized peptides, each containing two immunogenic MHC class I and one class II epitopes derived from the tumorigenic HPV proteins E6 and E7, were used. MAV was self-assembled with peptides at a 1:5 molar ratio. To assess antigen-specific immune response, we vaccinated C57BL/6J mice (n=12) intradermally in a prime-boost-boost schedule every two weeks. Splenic and lymph node derived lymphocytes were isolated and antigen-specific T cell responses were analyzed using flow cytometry at 6 weeks post vaccination. To evaluate efficacy, we inoculated C57BL/6J mice (n=10) with the epithelial TC-1 cell line that constitutively expresses the E6 and E7 proteins of HPV (20,000 cells/mouse) and vaccinated with VTX-067 on days 3, 17 and 24. Tumor size was measured twice per week and survival determined based on growth of the tumor to a specific volume (2,000 mm3). Results C57BL/6J mice vaccinated with VTX-067 generated significant CD8+IFNg+ responses at the three highest doses of VTX-067 treatment:130, 215 and 350 µg (p < 0.05, p < 0.0001 and p < 0.0001 respectively by ANOVA) and CD4+IFNg+ T cell responses at vaccine doses 215 and 350 µg (p < 0.0001) compared to saline-treated groups. Mice vaccinated with VTX-067 at doses of 80, 130, and 215 μg survived significantly longer with markedly slower tumor growth than mice in saline control groups (p < 0.0001; log-rank followed by Mantel-Cox tests). VTX-067 vaccination resulted in a significant tumor volume reduction at any of the three highest doses of VTX-067 compared to mice in the saline control group. In the 215 μg group, four of the 10 mice were tumor-free at the end of the study. Conclusions Overall, our study demonstrated that three dose levels of VTX-067 all provided significant antigen specific T cell responses, increases in overall survival and reduction of tumor volume. We believe these data, in addition to previously published work by our team on a Lassa Fever Virus vaccine,1 support the view that our self-assembling vaccine platform is potentially relevant to both infectious disease and cancer targets. Reference Leblanc P, Moise L, Luza C, Chantaralawan K, Lezeau L, Yuan J, Field M, Richer D, Boyle C, Martin WD, Fishman JB, Berg EA, Baker D, Zeigler B, Mais DE, Taylor W, Coleman R, Warren HS, Gelfand JA, De Groot AS, Brauns T, Poznansky MC. VaxCelerate II: rapid development of a self-assembling vaccine for Lassa fever. Hum Vaccin Immunother. 2014;10(10):3022–38. doi: 10.4161/hv.34413. PMID: 25483693; PMCID: PMC5443105.