Immunological responses in cancer patients after vaccination with the therapeutic telomerase-specific vaccine Vx-001

Abstract

Vx-001, an HLA-A*0201 restricted telomerase (TERT)-specific anti-tumor vaccine, is composed of the 9-mer cryptic TERT(572) peptide and its optimized variant TERT(572Y). We have previously shown that Vx-001 is non-toxic, highly immunogenic and in vaccinated NSCLC patients early specific immune response is associated with prolonged survival. The aim of the present study was to investigate the specific T-cell immune response against Vx-001. Fifty-five patients with chemo-resistant advanced solid tumors were vaccinated with TERT(572Y) (2 subcutaneous injections) followed by TERT(572) peptide (4 subcutaneous injections) every 3 weeks. Specific immune response was evaluated by IFN-γ and perforin ELISpot and intracellular cytokine staining assays. TERT-reactive T cells were detected in 27 (51%) out of 53 evaluable patients after the 2nd vaccination and in 22 (69%) out of 32 evaluable patients after the completion of 6 vaccinations. Immune responses developed irrespective of the stage of disease and disease status before vaccination. Patients with disease progression at study entry who developed a post-vaccination-induced immunological response had a significant overall survival benefit compared to the post-vaccination non-responders. The Vx-001 vaccine is a promising candidate for cancer immunotherapy since it can induce a TERT-specific T-cell immune response that is associated with prolonged survival.

Fig. 1

TERT₅₇₂-specific T-cell responses in patients vaccinated with Vx-001. a Frequencies of specific T cells to TERT peptides in vaccinated patients prior to vaccination and after the 2nd and 6th vaccination (post-vaccination) using IFN-γ ELISpot assay, and b IFN-γ intracellular staining, c TERT₅₇₂ and TERT_572Y reactive CD8⁺ T cells after the 2nd and 6th vaccination in two representative patients as assessed by IFN-γ ICS. Percentages in the dot plots are for CD3⁺ CD8⁺ IFN-γ⁺ T cells [***P < 0.0001; **P < 0.001 and *P < 0.05; SFC = spot-forming cells]

Fig. 2

a Frequencies of cytotoxic-specific T cells to TERT₅₇₂ peptide as assessed by perforin production in the post-vaccination samples of four representative patients using ELISpot. Dashed line represents the threshold for “positive” response [***P < 0.0001; **P < 0.001 and *P < 0.05; SFC = spot-forming cells] b The lytic activity of the sorted TERT_572Y-tetramer⁺/CD8⁺ T cells from one strongly responding patient was assessed by a chromium-release assay against TERT⁺ and TERT⁻ cell lines

Fig. 3

TERT₅₇₂-specific T-cell responses according to disease stage and disease status before study entry and disease evolution in vaccinated patients. Magnitude of T-cell response to TERT₅₇₂ peptide in vaccinated patients prior to vaccination and after the 2nd and 6th vaccinations (post-vaccination) according to the a disease stage and b disease status using ELISpot. [SFC = spot-forming cells; [***P < 0.0001; **P < 0.002, paired t test]

Fig. 4

Kinetics of TERT-specific T-cell response development after immunization. TERT-specific immune response during the course of six cycles of vaccination a and in boosted patients b as assessed by IFN-γ ELISpot assay c Immune response in two representative boosted patients after the 8th (#45) and 10th (#13) boosts as assessed by IFN-γ ICS. The data in the graphs are presented as the mean value of 3 independent experiments. Background frequencies have been subtracted. [SFC = spot-forming cells]

Fig. 5

Progression-free and overall survival of all vaccinated patients. The progression-free and overall survival of all patients was assessed according to the presence (green line) of absence (blue line) of TERT-specific immune response after the 2nd vaccination (a) and at the completion of the 6-vaccination protocol (b) Overall survival of vaccinated patients with PD at study entry according to post-vaccination immune response (c)

Fig. 5

Progression-free and overall survival of all vaccinated patients. The progression-free and overall survival of all patients was assessed according to the presence (green line) of absence (blue line) of TERT-specific immune response after the 2nd vaccination (a) and at the completion of the 6-vaccination protocol (b) Overall survival of vaccinated patients with PD at study entry according to post-vaccination immune response (c)