Encapsulation into sterically stabilised liposomes enhances the immunogenicity of melanoma-associated Melan-A/MART-1 epitopes

Abstract

Tumour-associated antigens (TAA)-specific vaccination requires highly immunogenic reagents capable of inducing cytotoxic T cells (CTL). Soluble peptides are currently used in clinical applications despite an acknowledged poor immunogenicity. Encapsulation into liposomes has been suggested to improve the immunogenicity of discrete antigen formulations. We comparatively evaluated the capacity of HLA-A2.1 restricted Melan-A/MART-1 epitopes in soluble form (S) or following inclusion into sterically stabilised liposomes (SSL) to be recognised by specific CTL, to stimulate their proliferation and to induce them in healthy donors' peripheral blood mononuclear cells (PBMC), as well as in melanoma-derived tumour-infiltrating lymphocytes (TIL). HLA-A2.1 þ , Melan-A/ MART-1-NA-8 melanoma cells served as targets of specific CTL in 51Cr release assays upon pulsing by untreated or human plasmatreated soluble or SSL-encapsulated Melan-A/MART-1 27 -35 (M27 -35) or 26 -35 (M26 -35) epitopes. These reagents were also used to stimulate CTL proliferation, measured as 3H-thymidine incorporation, in the presence of immature dendritic cells (iDC), as antigen-presenting cells (APC). Induction of specific CTL upon stimulation with soluble or SSL-encapsulated peptides was attempted in healthy donors' PBMC or melanoma-derived TIL, and monitored by 51Cr release assays and tetramer staining. Na-8 cells pulsing with SSL M27 -35 resulted in a five-fold more effective killing by specific CTL as compared with equal amounts of S M27 -35. Encapsulation into SSL also provided a partial (50%) protection of M27 -35 from plasma hydrolysis. No specific advantages regarding M26 -35 were detectable in these assays. However, at low epitope concentrations (p100 ng ml À1 ), SSL M26 -35 was significantly more effective in inducing CTL proliferation than S M26 -35, in the presence of iDC, as APC. Preincubation with iDC for 6 h virtually abolished the capacity of S M26 -35 to stimulate specific CTL proliferation, but only partially affected that of SSL M26 -35. Most importantly, SSL M26 -35 was able to enhance the induction of specific CTL in healthy donors PBMC and in melanoma-derived TIL as compared to S M26 -35. Taken together, our data indicate that encapsulation of TAA epitopes into SSL results in effective immunogenic formulations suitable for clinical use in active specific tumour immunotherapy.

Sterically stabilized liposomes targeting P21 (RAC1) activated kinase‑1 and secreted phospholipase A₂ suppress prostate cancer growth and metastasis

“…activated kinase-1 and secreted phospholipase A 2 suppress prostate cancer growth and metastasis ARTI VERMA 1,2* , WIDED NAJAHI-MISSAOUI 3* , BRIAN S. CUMMINGS 3,4 and PAYANINGAL R. SOMANATH 1,2,5 esterase overexpressed in several types of cancer, including PCa (17). SSL-IPA3 are long-circulating liposomes designed for passive targeting by the enhanced permeability and retention effect (18)(19)(20). The base formulation of these SSLs is clinically used for the enhanced delivery of doxorubicin for the treatment of breast cancer (21).…”

Particulate Systems as Adjuvants and Carriers for Peptide and Protein Antigens

“…Antigenic peptides encapsulated in sterically stabilized liposomes display a significantly higher capacity to resist plasma enzymatic hydrolysis, to stimulate T-cell proliferation, and to induce specific cytotoxic T-cell responses as compared to soluble antigen [73]. After oral administration of ovalbumin-encapsulating liposomes, unmodified liposomes tended to induce a stronger systemic immune response than the PEG-modified ones at the higher concentration of liposomes, whereas at the lower concentration, mucosal immune response was stronger for the PEG-modified liposomes [74].…”

Advanced Liposomal Vectors as Cancer Vaccines in Melanoma Immunotherapy

“…In the context of a melanoma immunotherapy program, sterically stabilized liposomes able to efficiently load and protect two epitopes derived from the Mart-1 melanoma differentiation antigen have been developed Adamina et al, 2004) and extensively tested in vitro. Further liposomal constructs encapsulating melanoma epitopes from gp100 and trp-2 antigens have also been produced by our group.…”