TLR4-mediated intestinal mucosal autoimmunity promotes post-transplant gut-derived invasive candidiasis via microfold cell impairment

Abstract

<p><strong>Background</strong> Invasive fungal infection (IFI) is a critical problem of high mortality for patients receiving liver transplantation. Gut-derived candidiasis caused by dysbiosis is the major source of IFI, and intestinal mucosa disruption is the first impaired defence line to microbe invasion, but the detailed mechanism stays unclear. Hence, we aim to investigate the intestinal mucosal mechanism during gut-derived invasive candidiasis and elicit a new preventive and therapeutic strategy.</p><p><strong>Methods</strong> A rat orthotopic liver transplantation model using whole-size and small-for-size grafts with <em>Candida albicans</em> gastrointestinal colonization will be established and the incidence and severity of invasive candidiasis will be determined by β-D-Glucan assay and blood culture. Phenotypically, intestinal mucosal epithelium integrity, microfold (M) cell population and immunologic pattern of Peyer’s patches (PP) will be investigated in the rat model. Mechanically, the expression of toll-like receptors (TLRs) of PP and their correlation with M cell population will be explored in the rat model. The role of TLRs in regulating mucosal homeostasis during invasive candidiasis will be further studied in TLR-specific knock-out mice.</p><p><strong>Results</strong> By comparison with sham and whole-size graft groups, liver transplants using small-for-size grafts showed an increased infection rate and lethality in the rat models (IDDF2022-ABS-0270 Figure 1A-B). The intestinal epithelium impairment indicated by loss of tight junction marker – Claudin-3 as well as villus collapse were shown more severe in the small-for-size group (IDDF2022-ABS-0270 Figure 1C). In addition, M cell was found to be significantly reduced in the small-for-size group and was associated with increased mRNA levels of TLR4 and CD8⁺ T cells in the PP (IDDF2022-ABS-0270 Figure1C-E). Mechanically, a specific blockade of M cell maturation showed increased candidiasis in the mouse model (IDDF2022-ABS-0270 Figure 1F). While knocking out TLR4 showed decreased invasive candidiasis rate, the restoration of M cell population, maintenance of FAE integrity, and decreased CD8⁺ T cell population (IDDF2022-ABS-0270 Figure 1G-I).</p>