Cascade Cytosol Delivery of Dual-Sensitive Micelle-Tailored Vaccine for Enhancing Cancer Immunotherapy

Enhancing cytosol delivery of exogenous antigens in antigen presenting cells can improve cross-presentation and CD8+ T cell-mediated immune response. The antigen cytosol delivery speed, which has great importance on the rate of MHC class I molecules (MHC I) antigen presentation pathway and cytotoxic T lymphocytes (CTLs) induction, has not been well studied. We hypothesized that micelle-tailored vaccine with multiple cascaded lysosomal responsive capabilities could accelerate lysosomal escape and enhance cancer immunotherapy. To test our hypothesis, we created a novel micellar cancer vaccine (ovalbumin-loaded pH/redox dual-sensitive micellar vaccine, OLM-D) by cleavable conjugation of an antigen with house-made amphiphilic poly(L-histidine)-poly(ethylene glycol) (PLH-PEG) in current study. OLM-D was supposed to achieve cascade cytosol delivery of ovalbumin through three steps in terms of (i) initial redox triggered ovalbumin release, (ii) promoted proton inflow and micelle disassembly, and (iii) speeded proton sponge effect and lysosome bulging/broke. Redox-sensitive antigen release and consequently accelerative OLM-D disassembly were confirmed by sodium dodecylsulphate polyacrylamide gel electrophoresis (SDS-PAGE), transmission electronic microscopy (TEM), particle sizes, zeta potentials, and in vitro Ova release evaluation. The speeded cytosol delivery of ovalbumin was visualized under a confocal laser scanning microscope (CLSM). The ability of OLM-D to increase the MHC I molecule combination rate and antigen cross-presentation efficiency was identified by antigen presentation assay and maturation assay in bone marrow-derived dendritic cells (BMDCs). In vivo, the capability of OLM-D to accumulate in draining lymph nodes (LNs) after injection was visualized by real-time near infrared fluorescence imaging (NIRF) and the distribution order in different LNs was first observed (a, d, c, b). Enhanced cancer immunity of OLM-D was confirmed by increased CD3+CD8+ T cell quantity, CD3+CD8+25D11.6+ T cells quantity, and IFN-gamma, IL-2 secretion post subcutaneous or intraperitoneal injection (p < 0.05). Taken together, our results indicated that OLM-D provided a promising cascade cytosol delivery strategy, which held great potential to guide further design of nano-particulate cancer vaccines for efficient cancer immunotherapy.