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h Trypanozoon parasites infect both humans, causing sleeping sickness, and animals, causing nagana, surra, and dourine. Control of nagana and surra depends to a great extent on chemotherapy. However, drug resistance to several of the front-line drugs is rising. Furthermore, there is no official treatment for dourine. Therefore, there is an urgent need to develop antiparasitic agents with novel modes of action. Host defense peptides have recently gained attention as promising candidates. We have previously reported that one such peptide, the equine antimicrobial peptide eCATH1, is highly active against equine Gram-positive and Gram-negative bacteria, without cytotoxicity against mammalian cells at bacteriolytic concentrations. In the present study, we show that eCATH1 exhibits an in vitro 50% inhibitory concentration (IC 50 ) of 9.5 M against Trypanosoma brucei brucei, Trypanosoma evansi, and Trypanosoma equiperdum. Its trypanocidal mechanism involves plasma membrane permeabilization and mitochondrial alteration based on the following data: (i) eCATH1 induces the rapid influx of the vital dye SYTOX Green; (ii) it rapidly disrupts mitochondrial membrane potential, as revealed by immunofluorescence microscopy using the fluorescent dye rhodamine 123; (iii) it severely damages the membrane and intracellular structures of the parasites as early as 15 min after exposure at 9.5 M and 5 min after exposure at higher concentrations (19 M), as evidenced by scanning and transmission electron microscopy. We also demonstrate that administration of eCATH1 at a dose of 10 mg/kg to T. equiperdum-infected mice delays mortality. Taken together, our findings suggest that eCATH1 is an interesting template for the development of novel therapeutic agents in the treatment of trypanosome infections.

Rhodococcus equi is one of the most important causes of mortality in foals between 1 and 6 months of age. Although rare, infection also occurs in a variety of other mammals including humans, often following immunosuppression of various causes. Secreted proteins are known to mediate important pathogen-host interactions and consequently are favored candidates for vaccine development as they are the most easily accessible microbial antigens to the immune system. Here, we describe the results of a proteomic analysis based on SDS-PAGE, immunoblot and mass spectrometry, which was carried out aiming the identification of secreted proteins that are differently expressed at 30 degrees C versus 37 degrees C and at mid-exponential versus early-stationary growth phase and antigenic proteins from R. equi ATCC 33701. A total of 48 proteins was identified regardless of growth conditions. The cholesterol oxidase ChoE appears to be the major secretory protein. Moreover, four proteins revealed high homologies with the mycolyl transferases of the Ag85 complex from Mycobacterium tuberculosis. The sequence analysis predicted that 24 proteins are transported by a signal peptide-dependent pathway. Moreover, five antigenic proteins of R. equi were identified by immunoblot, including a novel strongly immunoreactive protein of unknown function. In conclusion, the elucidation of the secretome of R. equi identified several proteins with different biological functions and a new candidate for developing vaccines against R. equi infection in horse.

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