Tumor Microenvironment-Regulating Immunosenescence-Independent Nanostimulant Synergizing with Near-Infrared Light Irradiation for Antitumor Immunity

Abstract

The combination of photothermal therapy (PTT) and toll-like receptor (TLR)-mediated immunotherapy can elicit antitumor immunity and modulate the immunosuppressive tumor microenvironment (TME). Unlike other TLRs, TLR-5 is a promising target for immune activation, as its expression is well-maintained even during immunosenescence. Here, we developed a unique tumor microenvironment-regulating immunosenescence-independent nanostimulant consisting of TLR-5 adjuvant <i>Vibrio vulnificus</i> flagellin B (FlaB) conjugated onto the surface to an IR 780-loaded hyaluronic acid-stearylamine (HIF) micelles. These HIF micelles induced immune-mediated cell death <i>via</i> PTT when irradiated with a near-infrared laser. In comparison with PTT alone, the combination of <i>in situ</i>-generated tumor-associated antigens produced during PTT and the immune adjuvant FlaB demonstrated enhanced vaccine-like properties and modulated the TME by suppressing immune-suppressive regulatory cells (Tregs) and increasing the fraction of CD103⁺ migratory dendritic cells, which are responsible for trafficking tumor antigens to draining lymph nodes (DLNs). This combinatorial strategy (<i>i.e.</i>, applying a TLR-5 adjuvant targeted to immunosenescence-independent TLR-5 and the <i>in situ</i> photothermal generation of tumor-associated antigens) is a robust system for next-generation immunotherapy and could even be applied in elderly patients, thus broadening the clinical scope of immunotherapy strategies.