Engineering of a self-adjuvanted iTEP-delivered CTL vaccine

Cytotoxic T lymphocyte (CTL) epitope peptide-based vaccines are widely used in cancer and infectious disease therapy. We previously generated an immune-tolerant elastin-like polypeptides (iTEPs)-based carrier to deliver a peptide CTL vaccine and enhance the efficiency of the vaccine. To further optimize the vaccine carrier, we intended to potentiate its function by designing an iTEP-based carrier that was able to deliver adjuvant and a vaccine epitope as one molecule. Thus, we fused a 9-mer H₁₀₀, a peptide derived from the high-mobility group box 1 protein (HMGB1) that could induce activation of dendritic cells (DCs), with an iTEP polymer to generate a new iTEP polymer named H₁₀₀-iTEP. The H₁₀₀-iTEP still kept the feature of reversible phase transition of iTEPs and should be able to be used as a polymer carrier to deliver peptide vaccines. The expression levels of CD80/CD86 on DCs were assessed using flow cytometry. The iTEP fusion-stimulated IL-6 secretion by DCs was measured with ELISA. Activation of antigen-specific CD8⁺ T cells induced by iTEP fusions was examined through a B3Z hybridoma cell activation assay. In vivo CTL activation promoted by iTEP fusions was detected by an IFN-γ-based ELISPOT assay. The iTEP fused with H₁₀₀ could induce maturation of DCs in vitro as evidenced by increased CD80 and CD86 expression. The iTEP fusion also promoted activation of DCs by increasing secretion of a proinflammatory cytokine IL-6. The N-terminus or C-terminus fusion of H₁₀₀ to iTEP had a similar effect and a reduced form of cysteine in iTEP fusions was required for DC stimulation. iTEP fusions potentiated a co-administrated CTL vaccine by increasing an antigen-specific CTL response in vitro and in vivo. When the H₁₀₀-iTEP was fused to a CTL epitope to generate a one-molecule vaccine, this self-adjuvanted vaccine elicited a stronger antigen-specific CTL response than a vaccine adjuvanted by Incomplete Freund's Adjuvant. Thus, we have successfully generated a functional, one-molecule iTEP-based self-adjuvanted vaccine.