Enhanced Vaccine Immunogenicity Enabled by Targeted Cytosolic Delivery of Tumor Antigens into Dendritic Cells.

Molecular vaccines comprising antigen peptides and inflammatory cues make up a class of therapeutics that promote immunity against cancer and pathogenic diseases but often exhibit limited efficacy. Here, we engineered an antigen peptide delivery system to enhance vaccine efficacy by targeting dendritic cells and mediating cytosolic delivery. The delivery system consists of the nontoxic anthrax protein, protective antigen (PA), and a single-chain variable fragment (scFv) that recognizes the XCR1 receptor on dendritic cells (DCs). Combining these proteins enabled selective delivery of the N-terminus of lethal factor (LFN) into XCR1-positive cross-presenting DCs. Incorporating immunogenic epitope sequences into LFN showed selective protein translocation in vitro and enhanced the priming of antigen-specific T cells in vivo. Administering DC-targeted constructs with tumor antigens (Trp1/gp100) into mice bearing aggressive B16-F10 melanomas improved mouse outcomes when compared to free antigen, including suppressed tumor growth up to 58% at 16 days post tumor induction (P < 0.0001) and increased survival (P = 0.03). These studies demonstrate that harnessing DC-targeting anthrax proteins for cytosolic antigen delivery significantly enhances the immunogenicity and antitumor efficacy of cancer vaccines.

Simultaneous amplification of multiple immunofluorescence signals via cyclic staining of target molecules using mutually cross-adsorbed antibodies.

Amplification of immunofluorescence (IF) signals is becoming increasingly critical in cancer research and neuroscience. Recently, we put forward a new signal amplification technique, which we termed fluorescent signal amplification via cyclic staining of target molecules (FRACTAL). FRACTAL amplifies IF signals by repeatedly labeling target proteins with a pair of secondary antibodies that bind to each other. However, simultaneous amplification of multiple IF signals via FRACTAL has not yet been demonstrated because of cross-reactivity between the secondary antibodies. In this study, we show that mutual cross-adsorption between antibodies can eliminate all forms of cross-reactions between them, enabling simultaneous amplification of multiple IF signals. First, we show that a typical cross-adsorption process-in which an antibody binds to proteins with potential cross-reactivity with the antibody-cannot eliminate cross-reactions between antibodies in FRACTAL. Next, we show that all secondary antibodies used in FRACTAL need to be mutually cross-adsorbed to eliminate all forms of cross-reactivity, and then we demonstrate simultaneous amplification of multiple IF signals using these antibodies. Finally, we show that multiplexed FRACTAL can be applied to expansion microscopy to achieve higher fluorescence intensities after expansion. Multiplexed FRACTAL is a highly versatile tool for standard laboratories, as it amplifies multiple IF signals without the need for custom antibodies.

FRACTAL: Signal amplification of immunofluorescence via cyclic staining of target molecules.

In this article, we demonstrate fluorescent signal amplification via cyclic staining of target molecules (FRACTAL), a technique that can amplify the signal intensity of immunofluorescence staining more than nine-fold via simple cyclic staining of secondary antibodies. We also show that FRACTAL is compatible with four-color imaging and expansion microscopy imaging.