Candida albicans is a major cause of human infections, ranging from relatively simple to treat skin and mucosal diseases to systemic life-threatening invasive candidiasis. Fungal infections treatment faces three major challenges: the limited number of therapeutic options, the toxicity of the available drugs, and the rise of antifungal resistance. In this study, we demonstrate the antifungal activity and mechanism of action of peptides ToAP2 and NDBP-5.7 against planktonic cells and biofilms of C. albicans. Both peptides were active against C. albicans cells; however, ToAP2 was more active and produced more pronounced effects on fungal cells. Both peptides affected C. albicans membrane permeability and produced changes in fungal cell morphology, such as deformations in the cell wall and disruption of ultracellular organization. Both peptides showed synergism with amphotericin B, while ToAP2 also presents a synergic effect with fluconazole. Besides, ToAP2 (6.25 µM.) was able to inhibit filamentation after 24 h of treatment and was active against both the early phase and mature biofilms of C. albicans. Finally, ToAP2 was protective in a Galleria mellonella model of infection. Altogether these results point to the therapeutic potential of ToAP2 and other antimicrobial peptides in the development of new therapies for C. albicans infections. Candida albicans is a fungal species present in the normal human microbiota, colonizing several areas of the body. However, under certain circumstances, this species may become a pathogen, causing diseases that can be life-threatening 1-4. The use of broad-spectrum antibiotics, immune suppression, or changes in the local host environments are examples of situations that may favor the proliferation of C. albicans and the onset of disease 5-8. Moreover, C. albicans ability to thrive in human tissues involves metabolic and morphological changes associated with the expression of different virulence factors 9. C. albicans virulence factors include secretion of enzymes, adhesion to cell surfaces and evasion of the immune system 10,11. Two virulence factors of major clinical importance are the fungal polymorphism and its ability to form biofilms 12-14. C. albicans ability to transit between yeast and filamentous forms is crucial for pathogenesis and both fungal forms are relevant for infection 15. For instance, hyphae have a major role on tissue invasion, whereas the yeast morphology facilitates fungal dispersion 16. The different fungal morphologies are also important for the formation of C. albicans biofilms 17. Living in biofilms confers to the microorganisms several advantages, when compared to the planktonic lifestyle, including protection against immune cells, increased resistance to antimicrobials agents and other chemical, physical and environmental stressors 18,19 .

Considering the importance of macrophages as the first line of defense against fungal infection and the different roles played by the two M1- and M2-like polarized macrophages, we decided to evaluate the effects of Paracoccidioides brasiliensis infection on GM-CSF- and M-CSF-induced bone marrow-derived macrophages (BMM) from the A/J and B10.A mouse strains, an established model of resistance/susceptibility to PCM, respectively. Upon differentiation, the generated GM- or M-BMMs were characterized by morphological analyses, gene expression profiles, and cytokines production. Our main results demonstrate that GM-BMMs derived from A/J and B.10 produced high levels of pro- and anti-inflammatory cytokines that may contribute to generate an unbalanced early immune response. In accordance with the literature, the B10.A susceptible mice lineage has an innate tendency to polarize into M1-like phenotype, whereas the opposite phenotype occurs in A/J resistance mice. In this context, our data support that susceptibility and resistance are strongly correlated with M1 and M2 polarization, respectively.