Variable epitope library carrying heavily mutated survivin-derived CTL epitope variants as a new class of efficient vaccine immunogen tested in a mouse model of breast cancer

Abstract

The antigenic variability of tumor cells leading to dynamic changes in cancer epitope landscape along with escape from immune surveillance by down-regulating tumor antigen expression/presentation and immune tolerance are major obstacles for the design of effective vaccines. We have developed a novel concept for immunogen construction based on introduction of massive mutations within the epitopes targeting antigenically variable pathogens and diseases. Previously, we showed that these immunogens carrying large combinatorial libraries of mutated epitope variants, termed as variable epitope libraries (VELs), induce potent, broad and long lasting CD8+IFN-γ+ T-cell response as well as HIV-neutralizing antibodies. In this proof-of-concept study, we tested immunogenic properties and anti-tumor effects of the VELs bearing survivin-derived CTL epitope (GWEPDDNPI) variants in an aggressive metastatic mouse 4T1 breast tumor model. The constructed VELs had complexities of 10,500 and 8,000 individual members, generated as combinatorial M13 phage display and synthetic peptide libraries, respectively, with structural composition GWXPXDXPI, where X is any of 20 natural amino acids. Statistically significant tumor growth inhibition was observed in BALB/c mice immunized with the VELs in both prophylactic and therapeutic settings. Vaccinated mice developed epitope-specific spleen cell and CD8+ IFN-γ+ T-cell responses that recognize more than 50% of the panel of 87 mutated epitope variants, as demonstrated in T-cell proliferation assays and FACS analysis. These data indicate the feasibility of the application of this new class of immunogens based on VEL concept as an alternative approach for the development of molecular vaccines against cancer.

A self-aggregating peptide: implications for the development of thermostable vaccine candidates

“…no. C1157) as previously described [43]. Cells were stimulated with concanavalin A (ConA) (3 μg mL − 1 ) (data not shown), GFP (10 μg mL − 1 ), PH (1-110) GFP (10 μg mL − 1 ) or Albumin (10 μg mL − 1 , as a non-related antigen), and finally incubated in flat-bottomed microtiter plates (5 × 10 5 cells/well), for 5 days at 37°C in a 5% CO 2 humidified atmosphere.…”

Antigenic variability: Obstacles on the road to vaccines against traditionally difficult targets

“…Considering that the TCR repertoire and cancer-derived epitopes are of random origin, the VELs carrying random mutations are perfectly suited as immunogens capable of dealing with antigenic variability. 107 We showed that VEL-based immunogens induce protective immune responses against mouse adenocarcinoma in both prophylactic and therapeutic settings. 107 We think that immunization with VELs may prevent or reduce the likelihood of epitope escape and, therefore, represents a realistic alternative to existing vaccine approaches targeting cancers that have high mutation rates such as melanoma, lung cancer or colon cancer or those with relatively fewer mutations such as glioblastoma or neuroblastoma.…”

“…107 We showed that VEL-based immunogens induce protective immune responses against mouse adenocarcinoma in both prophylactic and therapeutic settings. 107 We think that immunization with VELs may prevent or reduce the likelihood of epitope escape and, therefore, represents a realistic alternative to existing vaccine approaches targeting cancers that have high mutation rates such as melanoma, lung cancer or colon cancer or those with relatively fewer mutations such as glioblastoma or neuroblastoma. 77,108 Furthermore, due to the down regulation of MHC molecules in tumor cells, the immunization with VELs may lead to the selection of more "fit" TCRs as a result of competition between peptides for binding to MHC in tumors and the presence of unusually diverse and large pool of newly activated T cells.…”

“…77,108 Furthermore, due to the down regulation of MHC molecules in tumor cells, the immunization with VELs may lead to the selection of more "fit" TCRs as a result of competition between peptides for binding to MHC in tumors and the presence of unusually diverse and large pool of newly activated T cells. 107 In addition, competitive binding of cognate peptide epitopes to MHC within APCs could be beneficial for the induction and maturation of protective immune responses which are difficult to generate when conventional Ags, such as defined antigenic sequence immunogens (DASIs) regularly leading to activation of both B and T cells with reduced repertoire, are used.…”

“…105,106 Owing to the clear similarity between AVPs and cancer cells, we recently tested the prophylactic and therapeutic efficacy of vaccine immunogens bearing VELs of survivin-derived CTL epitope/peptide in an aggressive metastatic mouse 4T1 breast tumor model. 107 The rationale was that the immunization with VELs carrying a large number of survivin-derived epitope variants will lead to simultaneous presentation of altered/mutated epitopes to immune system and will induce the activation of diverse and broad repertoire of T cells capable of recognizing cancer epitopes present at the time of experimental or spontaneous induction of tumor as well as the variants that would appear later upon disease progression (Fig. 1).…”