Cell-Penetrating Peptides Assisted Nanovaccine Promote Antigen Cross-presentation and anti-Tumor Immune Response

Exogenous antigens processing in the cytosol and subsequently cross-presentation on major histocompatibility complex class I (MHC-I) molecules activates cytotoxic CD8+ lymphocytes (CTL) which are crucial in cancer immunotherapy. Here, we report a nanovaccine, which is produced by encapsulating OVA (ovalbumin, a model antigen) chemically modified with MPGΔNLS (MPGΔNLS-OVA conjugate) into poly (lactide-co-glycolide) acid (PLGA) nanoparticles. We hypothesized that after nanovaccine uptaken into immune cells, MPGΔNLS, one type of cell-penetrating peptides, would assist antigens to escape from lysosome into the cytosol, increase the amount of antigens procession in the cytosol and subsequently enhance antigen cross-presentation via MHC-I molecules and elicit cytotoxic CD8+ T cell responses. The results of in vitro experiments demonstrated MPGΔNLS-OVA-loaded PLGA NPs not only elevated release of OVA into the cytosol of dendritic cells (DCs), but also promoted DCs maturation and activation. It was also observed in mice vaccinated with MPGΔNLS-OVA-loaded PLGA NPs that MPGΔNLS modification could stimulate expansion of OVA-specific T-cells, generation of OVA-specific IgG antibodies and proliferation of OVA-specific memory T cells. Moreover, treatment of E.G7-OVA tumours-bearing mice with MPGΔNLS-OVA-loaded PLGA NPs resulted in significantly suppressed tumour growth and prolonged survival period of mice, compared to treatment with unmodified OVA-PLGA NPs or free OVA. In summary, cell-penetrating peptides linked with antigens that are encapsulated in PLGA nanoparticles as nanovaccines can spatiotemporally affect intracellular localization of antigens, promote antigens cross-presentation and stimulate antigen-specific immune responses, especially CTL responses, serving as an innovative approach to enhancing the efficacy of nanovaccine for cancer immunotherapy.