Paracoccidioides lutzii Infects Galleria mellonella Employing Formamidase as a Virulence Factor.

The formamidase (FMD) enzyme plays an important role in fungal thriving by releasing a secondary nitrogen source as a product of its activity. In Paracoccidioides species, previous studies have demonstrated the upregulation of this enzyme in a wide range of starvation and infective-like conditions. However, Paracoccidioides lutzii formamidase has not yet been defined as a virulence factor. Here, by employing in vivo infections using an fmd-silenced strain in Galleria mellonella larvae model, we demonstrate the influence of formamidase in P. lutzii's immune stimulation and pathogenicity. The formamidase silencing resulted in improper arrangement of the nodules, poor melanogenesis and decreased fungal burden. Thus, we suggest that formamidase may be a piece composing the process of molecular recognition by Galleria immune cells. Furthermore, formamidase silencing doubled the observed survival rate of the larvae, demonstrating its importance in fungal virulence in vivo. Therefore, our findings indicate that formamidase contributes to Galleria's immune incitement and establishes the role of this enzyme as a P. lutzii virulence factor. Author summary: The study of fungal neglected pathogens is of significant importance for the elucidation of the mechanisms underlying the diseases they cause. The Paracoccidioides lutzii fungus is a pathogen endemic to Latin America, which causes disease in vulnerable portions of society. To cause the disease, the fungal cells must overcome the immune system and obtain nutrients that are typically withdrawn by the host. In this regard, different molecules are crucial for the establishment of infection. The formamidase enzyme plays a role in the survival of the fungus P. lutzii. Our study, presented below, demonstrates that formamidase silencing affects the immune response of G. mellonella larvae to the fungus, resulting in impairment of nodule formation, diminished melanin production, and a reduction in fungal burden. Furthermore, silencing formamidase expression in P. lutzii doubles the survival rate of larvae infected by the fungus, showing its importance for these yeast cells to infect this animals. [ABSTRACT FROM AUTHOR]