Utilização de peptídeos sintéticos derivados de moléculas imunodominantes de Toxoplasma gondii para diagnóstico sorológico da toxoplasmose em ovinos e galinhas caipiras

Chapter I - The obligate intracellular parasite Toxoplasma gondii is the causative agent of toxoplasmosis, a disease that affects humans and generates economic losses in farm animals. When prevention fails disease refers to the diagnosis and subsequent treatment if the individual is diagnosed as positive. Therefore, the development of new accurate diagnostic tools for detecting T. gondii infection is a need in particular to determine the environmental source of infection which can result in more appropriate public health policies against different routes of infection and prevent potential damage that toxoplasmosis can cause when animals are infected. Chapter II - The domestic chicken (Gallus gallus domesticus) are considered epidemiological sentinels, still representing a major source of recombinant strains when predated by cats, it is common to find them with multiple infections. We evaluate the diagnostic potential of six synthetic peptides (SAG2Y, MIC1, M2AP, GRA10, ROP2 and ROP7) predicted in silico from tachyzoites immunodominant markers of T. gondii in samples from naturally infected chickens, comparing synthetic peptides with antigen total soluble (STAg). In general, our results demonstrated that reactivity rates and positivity for these peptides are similar to the STAg, and the ROP7 peptide and the combination of peptides MIC1+ROP2 have significant sensitivity, confirming them as potential diagnostic tools for the diagnosis of toxoplasmosis in chickens. Chapter III - Sheep (Ovis aries) are commonly infected with Toxoplasma gondii due to his eating habits. Infection in pregnant sheep can have serious consequences such as embryonic death, fetal resorption, mummification, and neonatal death. One concern regarding the infection in these animals is that the meat can be a source of contamination to humans and other carnivores. Therefore perform accurate diagnosis in these animals is of fundamental importance. In the present study we evaluated the potential of new synthetic peptides as a diagnostic tool. Synthetic peptides (SAG2Y, SRS52A, MIC14, GRA4, GRA10 and GRA15) were predicted in silico from immunodominant proteins of T. gondii. We determine the levels of IgG antibodies using sera obtained from two farms in the city of Uberlândia. Analyzing the results together, the peptide combination GRA10+GRA15 (Accuracy = 0,82) showed better characteristics compared with the other mixtures. This preparation could be better analyzed with an antigenic mixture potential use in the diagnosis of toxoplasmosis in sheep and other species.

Manipulação gênica do protozoário Neospora caninum como ferramenta para o estudo das interações parasito-hospedeiro

Neospora caninum is an obligate intracellular parasite classified in the phylum Apicomplexa, characterized by the presence of the apical complex composed by micronemes proteins, rhoptries and dense granules, used by parasite during the adhesion and invasion process of the host cell. This is the mean event in infection pathogenesis generated by N. caninum and other parasites from the phylum Apicomplexa, promoting influence in the parasite biology and the interface between the parasite and its host. Therefore, molecular tools have been developed in order to identify and characterize these possible virulence factors. Thus, the present study sought to establish a specific system of genetic manipulation of N. caninum, searching for the improvement of the genetics manipulation of this parasite. So, we developed genetically depleted N. caninum to Rop9 rhoptry using the pU6-Universal CRISPR-Cas9 plasmid of T. gondii modified by the insertion of Ku80. The Rop9 depleted parasite showed important during initial phase of invasion and replication of the parasite, however it was not characterized as a potential virulence fator for N. caninum. Furthermore, T. gondii proteins were expressed in N. caninum by the use of specific vectors for this parasite, showing an heterologous system for the study of Toxoplasma proteins, due to the fact that Gra15 or Gra24 of type II T. gondii and Rop16 of type I T. gondii were expressed in N. caninum tachyzoites in a stable way and keept its biological phenotype, as already presented the former parasite, that naturaly expresses these proteins. In addition, it was observed that N. caninum induced an inflammasome activation through NLRP3, ASC and Caspase-1. IL-1R/MyD88 demonstrated an indirect pathway in the control of parasite replication. Furthermore, it was observed that this activation is dependent of the potassium efflux and that different strains of N. caninum keep this activation profile. However, T. gondii strains block this activation, making necessary a prior signal in order to active the inflamosome pathway. Type I T. gondii Rop16 was identified as responsible for blocking this activation, in a dependent way to the STAT3 activation. Therefore, the development of molecular tools and their application in N. caninum may prove to be useful to identify and characterize virulent factors involved in the pathogenesis by these two protozoans.