The antimicrobial peptide MK58911-NH2 acts on planktonic, biofilm and intramacrophage cells of Cryptococcus neoformans

23 Cryptococcosis is associated with high rates of morbidity and mortality, especially in 24 AIDS patients. Its treatment is carried out by combining amphotericin B and azoles or 25 flucytosine, which cause unavoidable toxicity issues to the host. Thus, the urgency in 26 obtaining new antifungals drives the search for antimicrobial peptides (AMPs). This 27 study aimed to extend the understanding of the mechanism of action of an AMP analog 28 from wasps peptide toxins, MK58911-NH2, on Cryptococcus neoformans. It was also 29 evaluated if MK58911-NH2 can act on cryptococcal cells in macrophages, biofilms, and 30 an immersion zebrafish model of infection. Finally, we investigated the structure31 antifungal action and the toxicity relation of MK58911-NH2 fragments and a derivative 32 of this peptide (MH58911-NH2). The results demonstrated that MK58911-NH2 did not 33 alter the fluorescence intensity of cell wall binding dye calcofluor or capsulebinding 34 dye 18b7 antibody-FITC of C. neoformans, but rather reduced the number and size of 35 fungal cells. This activity reduced the fungal burden of C. neoformans both in 36 macrophages and in zebrafish embryos as well as within biofilms. Three fragments of 37 the MK58911-NH2 peptide showed no activity against Cryptococcus or toxicity in lung 38 cells. The derivative peptide MH58911-NH2, in which the lysine residues of MK5891139 NH2 were replaced by histidine, reduced the activity against extracellular and 40 intracellular C. neoformans. On the other hand, it was active against biofilm, and 41 reducing toxicity. In summary, the results showed that peptide MK58911-NH2 could be 42 a promising agent against cryptococcosis. The work also opens a perspective for the 43 verification of the antifungal activity of other derivatives. 44