In Vivo Visualization of Tumor Antigen-containing Microparticles Generated in Fluorescent-protein-elicited Immunity

Abstract

In vivo optical spatio-temporal imaging of the tumor microenvironment is useful to explain how tumor immunotherapies work. However, the lack of fluorescent antigens with strong immunogenicity makes it difficult to study the dynamics of how tumors are eliminated by any given immune response. Here, we develop an effective fluorescent model antigen based on the tetrameric far-red fluorescent protein KatushkaS158A (tfRFP), which elicits both humoral and cellular immunity. We use this fluorescent antigen to visualize the dynamic behavior of immunocytes as they attack and selectively eliminate tfRFP-expressing tumors in vivo; swarms of immunocytes rush toward tumors with high motility, clusters of immunocytes form quickly, and numerous antigen-antibody complexes in the form of tfRFP+ microparticles are generated in the tumor areas and ingested by macrophages in the tumor microenvironment. Therefore, tfRFP, as both a model antigen and fluorescent reporter, is a useful tool to visualize specific immune responses in vivo.

Circulating Tumor Microparticles Promote Lung Metastasis by Reprogramming Inflammatory and Mechanical Niches via a Macrophage-Dependent Pathway

“…The presence of T-MPs in tumor microenvironments is a general pathophysiological phenomenon (40). Such continuously produced T-MPs in the interstitial fluid of extracellular space may enter lymph or papillary vessels.…”

Biophotonics in China

“…It was found that the combined system outperformed the single system, and it was suitable for quantitative three‐dimensional imaging of the fluophor . Furthermore, aiming at the significant demand for the visualization research of tumor immunity, they developed multiscale optical imaging approaches , optimized red‐shift fluorescent protein probes , established multicolor labeling animal models, and achieved the in vivo visualization of specific antitumor immune response and immunotherapy .…”

Melittin-lipid nanoparticles target to lymph nodes and elicit a systemic anti-tumor immune response

“…Further, we assessed the ability of α-melittin-NPs to induce the apoptosis and necrosis of tumor cells and the release of endogenous tumor antigens in vivo. tfRFP-B16F10 tumor cells that expressed tetrameric far-red fluorescent protein (tfRFP) were used to visualize the release of endogenous antigens 32 . The fluorescence imaging of tumor tissue sections showed that both melittin and α-melittin-NPs induced the disappearance of fluorescent model antigens in the tumor section after 24 h, indicating the changes in membrane penetrability and the release of the tumor antigens ( Supplementary Fig.…”