Promotion of CTL epitope presentation by a nanoparticle with environment-responsive stability and phagolysosomal escape capacity.

Vaccines that induce cytotoxic T lymphocyte (CTL)-mediated immune responses constitute an important class of medical tools to fend off diseases like infections and malignancy. Epitope peptides, as a format of CTL vaccines, are being tested preclinically and clinically. To elicit CTL responses, epitope vaccines go through an epitope presentation pathway in dendritic cells (DCs) that has multiple bottleneck steps and hence is inefficient. Here, we report the development of a strategy to overcome one of these barriers, phagolysosomal escape in DCs. First, we furnished a previously established carrier-an immune-tolerant elastin-like polypeptide nanoparticle (iTEP NP)-with the peptides that are derived from the DNA polymerase of herpes simplex virus 1 (Pol peptides). Pol peptides were reported to facilitate phagolysosomal escape. In this study, while we found that Pol peptides promoted the CTL epitope presentation; we also discovered Pol peptides disrupted the formation of the iTEP NP. Thus, we engineered a series of new iTEPs and identified several iTEPs that could accommodate Pol peptides and maintain their NP structure at the same time. We next optimized one of these NPs so that its stability is responsive to its redox environment. This environment-responsive NP further strengthened the CTL epitope presentation and CTL responses. Lastly, we revealed how this NP and Pol peptides utilized biological cues of phagolysosomes to realize phagolysosomal escape and epitope release. In summary, we developed iTEP NP carriers with a new phagolysosomal escape function. These carriers, with their priorly incorporated functions, resolve three bottleneck issues in the CTL epitope presentation pathway: vaccine uptake, phagolysosomal escape, and epitope release.