Immunogen display on virus-like particles assembled from redesigned transcription activator-like effector proteins and nucleic acids: Activation of antigen-presenting cells.

Virus-like particles (VLPs) assembled from designed proteins are considered for eliciting immune responses. While many of VLPs assembled from designed proteins are spherical and lack a nucleic acid cargo, we show that our recently designed artificial capsid protein NucleoX11 self-assembles around single double-stranded nucleic acid fragments, forming rod-shaped VLPs whose length can be easily determined depending on the size of the template nucleic acid. To explore these designed VLPs as a vaccine platform, we have successfully incorporated the SpyCatcher003 peptide into NucleoX11 protein sequence via genetic fusion, thereby enabling the decoration of self-assembled VLPs with SpyTagged antigens. We show that SpyCatcher003_NucleoX11 VLPs are stable in both decorated and undecorated versions, forming self-assembled rod-shaped VLPs when incubated with 250 bp double-stranded DNA or poly I:C double-stranded RNA fragments. The antigen-decorated VLPs are efficiently taken up by antigen-presenting cells (APCs) in a dose-dependent manner and enhance the expression of the immune activation markers CD80 and CD86 molecules, which are crucial for activating naïve antigen specific T cells. These results demonstrate the potential of our construct as a versatile platform for the production of size-customizable VLPs with clinical application, such novel vaccine platform or drug-delivery systems.