The Immunomodulatory Effects of Metarhizium anisopliae Extract on Human Peripheral Blood Mononuclear Cells

In addition to their role as entomopathogenic fungi, Metarhizium spp. are also present as endophytes within plants. Hence, plant-based food products may contain fungal residues, whose consumption may entail potential risks to human health. The current investigation explores the effects of direct exposure to a combination of extracellular metabolites derived from Metarhizium anisopliae ARSEF7487, with dtx A as the predominant destruxin (dtx), on peripheral blood mononuclear cells (PBMCs). Although the treatment with M. anisopliae extracellular metabolite mixture at a concentration of 1 and 10 ng mL⁻1 was not found to induce toxic effects on the human PBMCs, it nevertheless had significant effects, particularly with regard to the host defense mechanisms. Exposure resulted in a 1.3-fold increase in TLR8 mRNA expression and a 3.4-fold increase in TLR9 mRNA. In addition, the PBMCs demonstrated greater mRNA expression of certain cytokines, specifically IL23A (10.7-fold) and IL1B (3.1-fold). Furthermore, treatment with destruxins resulted in a slight increase (1.5 ×) in levels of reactive oxygen species (ROS). The study indicates that extended exposure to dtxs, such as those derived from plant-based foods, does not adversely affect immune system cells; however, it significantly modulates their immune gene expression, particularly involving pattern recognition receptors (PRRs) and pro-inflammatory cytokines/chemokines.