Avaliação e caracterização da atividade anti-Toxoplasma gondii de peptídeos bioativos

Abstract

The zoonotic protozoan Toxoplasma gondii is the etiologic agent of toxoplasmosis, a cosmopolitan disease that affects one third of the world population. For most immunocompetent individuals, toxoplasmosis manifests itself in a variable way. In this group, the clinical manifestations, when present, may show a polysymptomatic condition, with fever, lymphadenopathy, ganglion involvement, myalgia, uveitis and chorioretinitis, where the severity of the manifestations will depend mainly on the host's protective immunity and the type of parasite strain. Within the risk group, the most severe form is found in newborn children, being characterized by necrotic and inflammatory lesions that can lead to neurological sequelae and can cause chorioretinitis, encephalitis and hydrocephalus. In addition, toxoplasmosis has a severe evolution in individuals with compromised immune systems (organ recipients, individuals undergoing chemotherapy and HIV). The therapies currently available for the treatment of toxoplasmosis have limited efficacy, require prolonged courses and demonstrate significant toxicity with serious side effects in individuals. In this regard, it is essential to concentrate efforts to search for new therapies that are more effective against T. gondii and less toxic to the host. Thinking about this perspective, antimicrobial peptides (AMPs) appear. These are molecules that make up the innate immunity of multicellular organisms (fungi, plants, insects, fish, amphibians, arachnids and mammals) and can be expressed constitutively, induced or as products of secondary metabolism. AMPs do not depend on interaction with a specific receptor, making them alternative therapeutic options with respect to antibiotics found commercially available. In this context, this work addressed the potential use of different bioactive peptides belonging to the family of phenylseptins, lycotoxin and surfactin as a new therapeutic source against T. gondii. For this purpose, cell cytotoxicity tests were carried out in NDHF neonatal human fibroblasts using the MTS colorimetric method. Activity Anti-T gondii was evaluated by means of invasion, proliferation and pretreatment tests of NDHF cells using parasites of the RH strain of T. gondii. Firstly, the cytotoxicity test was performed on NDHF cells. Concentrations greater than 100 μg /ml of D-Phes and L-Phes have shown significant toxicity, whereas for LyeTx and Surfactina concentrations above 12 μg/ml and 57.4 μg/ml, respectively, have already been toxic. The highest non-toxic concentrations of the peptides were then used in the subsequent steps: Results obtained after the treatment of intracellular T. gondii tachyzoites with the highest tested non-toxic concentrations showed that 100 μg/ml of D-Phes and L-Phes inhibited proliferation in 36.56 % and 28.1 %, respectively; 3 μg/ml LyeTx and 28.7 μg/ml Surfactin inhibited proliferation by 75.48 % and 80.4 %, respectively. The tests of the effect of the treatment on the invasion of parasites by the host cell showed a reduction of 43.24%, 50.8 %, 23.8 % and 53.3% in the invasion after incubation with 100 μg/ml of D-Phes and L- Phes, 3 μg/ml of LyeTx and 28.7 μg/ml of surfactin, respectively. Analyzes by optical microscopy again showed that treatment with 100 μg/ml of D-Phes significantly inhibited the invasion of T. gondii, reducing the number of infected cells by about 70% compared to the control. Our results show that AMPs could be an alternative to developing new therapies for toxoplasmosis.