Beneficial therapeutic effects with different particulate structures of murine polyomavirus VP1-coat protein carrying self or non-self CD8 T cell epitopes against murine melanoma

Abstract

Polyomavirus-like-particles (PLPs) are empty, non-replicative, non-infectious particles that represent a potent antigen-delivery system against malignant disease. Protective anti-tumour immunity can be induced under therapy conditions by subcutaneous (s.c.) treatment with particulate antigenic structures like chimerical polyomavirus-pentamers (PPs). These PPs displaying an immunodominant H-2Kb-restricted ovalbumin (OVA)257-264 epitope evoked nearly complete tumour remission in MO5 (B16-OVA) melanoma-bearing C57BL/6 mice by two s.c. applications in a weekly interval. The immunotherapeutic intervention started at day 4 after melanoma implant. Furthermore, 40% of melanoma-bearing mice vaccinated with heterologous PPs carrying a H-2Kb-restricted cytotoxic T lymphocyte (CTL) epitope derived from of tyrosinase-related protein 2 (TRP2) survived similar treatment conditions. However, a late immunotherapeutic onset at day 10 post melanoma inoculation revealed no significant differences between the therapeutic values (40-60% survival) of VP1-OVA252-270 and VP1-TRP2180-192 PPs, respectively. These experiments underlined the capacity of PPs to break T cell tolerance against a differentially expressed self-antigen. As a correlate for preventive and therapeutic immunity against MO5 melanoma the number of OVA257-264- or TRP2180-188-specific CD8 T cells were significantly increased within the splenocyte population of treated mice as measured by H-2Kb-OVA257-264-PE tetramer staining or appropriate ELISPOT assays, respectively. These results reveal that heterologous PLPs and even chimerical PPs represent highly efficient antigen carriers for inducing CTL responses underlining their potential as immunotherapeutics against cancer.

Exuberated Numbers of Tumor-Specific T Cells Result in Tumor Escape

“…Cytotoxicity assays were performed as previously described (8,9) In the OT-I TCR transgenic mice, >90% of the CD8 T cells express a transgenic TCR specific for the H-2K b -SIINFEKL complex (11). These T cells efficiently lyse MO5 tumor cells in vitro and in various preclinical models (6,12,13).…”

Adjuvant Combination and Antigen Targeting as a Strategy to Induce Polyfunctional and High-Avidity T-Cell Responses against Poorly Immunogenic Tumors

“…Several approaches have been used to induce immune responses able to reject B16 melanoma. They are based on the use of DC pulsed or expressing different types of antigens (14)(15)(16) or complex immunogens such as recombinant viruses, bacteria, or virus-like particles which contain many DC-activating signals (17)(18)(19). All these data prompted us to develop an immunotherapeutic strategy to treat B16-OVA established tumors using combinations of adjuvants and antigens.…”

Co-expression of P1A35-43/β2m fusion protein and co-stimulatory molecule CD80 elicits effective anti-tumor immunity in the P815 mouse mastocytoma tumor model

“…Peptide/MHC tetramer analysis and the ELISPOT assay have been widely used to assess antigen-specific T cell responses (28,29). To investigate the potential mechanism involved in the differences in tumorigenicity of gene-modified P815 cells, we analyzed the P1A-specific CD8 + T cell responses using the H-2L d /LPYLGWLVF pentamer analysis and mouse IFN-Á ELISPOT assay.…”