Candida albicans is a major fungal pathogen in humans. Novel antifungal agents are urgent demanded due to the challenges of the resistance. Antimicrobial peptides (AMPs) are critical components of the innate immune system against pathogenic microorganism infection. MAF-1A is a novel cationic AMP that comes from Musca domestica and is effective against C. albicans, but the antifungal mechanism remains unclear. In this study, we performed a transcriptomics analysis in C. albicans using RNA-seq technique under the treatment of MAF-1A. A total of 5654 genes were identified. Among these, 1032 were differentially expressed genes (DEGs), including 575 up-regulated genes and 457 down-regulated genes. In these DEGs, genes encoding ergosterol metabolism and fatty acid biosynthesis were identified to be significantly down-regulated, while genes associated with oxidative stress response and cell wall were identified to be significantly up-regulated. Using pathway enrichment analysis, 12 significant metabolic pathways were identified, and ribosome, oxidative phosphorylation, citrate cycle were mainly involved. The results revealed that MAF-1A induces complex responses in C. albicans. This study provides evidence that MAF-1A may inhibit the growth through affect multi-targets in C. albicans cells.

No abstract

Antimicrobial peptides (AMPs) are cationic small peptide chains that have good antimicrobial activity against a variety of bacteria, fungi, and viruses. AMP-17 is a recombinant insect AMP obtained by a prokaryotic expression system. However, the full antifungal activity, physicochemical characteristics, and cytotoxicity of AMP-17 were previously unknown. AMP-17 was shown to have good antifungal activity against five pathogenic fungi, with minimum inhibitory concentrations (MIC) of 9.375–18.75 μg/ml, and minimum fungicidal concentrations (MFC) of 18.75–37.5 μg/ml. Notably, the antifungal activity of AMP-17 against Cryptococcus neoformans was superior to that of other Candida spp. In addition, the hemolytic rate of AMP-17 was only 1.47%, even at the high concentration of 16 × MIC. AMP-17 was insensitive to temperature and high salt ion concentration, with temperatures of 98°C and –80°C, and NaCl and MgCl2 concentrations of 50–200 mmol/l, having no significant effect on antifungal activity. However, AMP-17 was sensitive to proteases, trypsin, pepsin, and proteinase K. The elucidation of antifungal activity, physicochemical properties and cytotoxicity of AMP-17 provided an experimental basis for its safety evaluation and application, as well as indicated that AMP-17 might be a promising drug.

No abstract

Housefly, Musca domestica, has a complicated immune system. However, its underlying operating mechanism remains elusive. Candida albicans is a major pathogen affecting humans by causing deep infection fungous disease, but it is non-symbiotic in houseflies. To investigate the C. albicans infection process in housefly, the changes in morphological and histological and expression patterns of antimicrobial peptide were monitored to indicate the insect's response to fungal infection. The results showed that scattered brown spots were comprising melanized encapsulation and encapsulated fungal cells were initially observed at the inner side of larvae's body wall 3 h postinfection (PI). Between 6 and 36 h PI, the whole body of larvae was densely covered with the brown spots, which then gradually disappeared. The majority had disappeared at 48 h PI. Some fungi colonized in the gaps between the body wall and the muscle layer, as well as among muscle fibers of the muscle layer at 12 h PI and hyphal was observed at 18 h PI. These fungi colonized distribution changed from a continuous line to scattered spots at 24 h PI and virtually disappeared at 48 h. The results of quantitative PCR analysis revealed that in coordination with the variation during the infection, the expression levels of four antimicrobial peptides were up-regulated. In conclusion, C. albicans infection in M. domestica larvae involved the following stages: injection, infection, immune response and elimination of the pathogen. The rapid response of antimicrobial peptides, melanized encapsulation and agglutination played a vital role against the pathogenic invasion.