Viability Assay of <em>Trichoderma stromaticum</em> Conidia Inside Human Peripheral Blood Mononuclear-Derived Macrophages

Macrophages represent a crucial line of defense and are responsible for preventing the growth and colonization of pathogens in different tissues. Conidial phagocytosis is a key process that allows for the investigation of the cytoplasmic and molecular events involved in macrophage-pathogen interactions, as well as for the determination of the time of death of internalized conidia. The technique involving the phagocytosis of fungal conidia by macrophages is widely used for studies evaluating the modulation of the immune responses against fungi. The evasion of phagocytosis and escape of phagosomes are mechanisms of fungal virulence. Here, we report the methods that can be used for the analysis of the phagocytosis, clearance, and viability of T. stromaticum conidia, a fungus which is used as a biocontrol and biofertilizer agent and is capable of inducing human infections. The protocol consists of 1) Trichoderma culture, 2) washing to obtain conidia, 3) the isolation of peripheral blood mononuclear cells (PBMCs) using the polysucrose solution method and the differentiation of the PBMCs into macrophages, 4) an in vitro phagocytosis method using round glass coverslips and coloration, and 5) a clearance assay to assess the conidia viability after conidia phagocytosis. In summary, these techniques can be used to measure the fungal clearance efficiency of macrophages.