Triagem in silico de candidatos vacinais contra Toxoplasma gondii
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2018-03-06
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Universidade Federal de Goiás
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Toxoplasma gondii is the causative agent of congenital toxoplasmosis, which manifests as mild chorioretinitis, miscarriage, mental retardation, microcephaly, hydrocephalus, and seizures. Treatment of this disease is limited and a new vaccine represents the best strategy for prevention of the infection. In the present study, the reverse vaccinology combined with immunomics was applied for the development of a vaccine against T. gondii. Using an in silico approach, we identified T. gondii’s proteins that contain signal peptide and transmembrane domain using the ToxoDB® database. We evaluated the homology of these proteins with the human proteome and predicted their epitopes using Blastp, NetMHCpan 3.0 and NetMHCIIpan 3.1 tools. Class I and II HLA alleles with frequency greater than 1% in the population of South America, North America and Europe were obtained using the dbMHC database. Processing of the MHC class I epitopes were evaluated by MHC I Processing on the IEDB® database and the B lymphocyte epitopes were obtained through the Bcpred and BCTOPE servers. Finally, the antigenicity of the potential targets was analyzed by the VAxiJen server. A total of 1228 proteins were obtained, from which 349 showed no homology with human proteins. For the South American population, among the proteins identified with promiscuous epitopes, we observed proteins that are part of the virulence arsenal of the pathogen such as ROP8, ROP7, ROM4, Cathepsin C / B, rhoptry neck protein and LMBR1 family region protein. In the North American and European populations, we identified common proteins to both populations, such as MIC15, ROP7, HECT-domain (ubiquitin-transferase) domain-containing protein and rhoptry neck protein. ROP31 and subtilisin SUB2 are exclusive to the North American population. These proteins are involved in the invasion process and were shown to be positive in all the parameters adopted in this study. Regarding B lymphocyte epitopes, proteins such as ROP7, ROP8, ROM4, MIC15, HECT were identified. These proteins also presented promiscuous epitopes to class I and II HLAs from the analyzed populations. In addition, MIC2, ROM5, ROP9, MIC8, and MIC9 also showed B lymphocyte epitopes, but MIC9 was noteworthy with the highest score, high expression in the bradyzoite stage, and lack of vaccine test. ROP7, ROP8, ROM4, MIC8 and MIC9 were selected for in vivo and in vitro testing. Thus, our results demonstrate that immunochemical reverse vaccination has been shown not only to identify potential vaccine candidates against pathogens with complex life cycles.
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INACIO, M. M. Triagem in silico de candidatos vacinais contra Toxoplasma gondii. 2018. 96 f. Dissertação (Mestrado em Genética e Biologia Molecular) - Universidade Federal de Goiás, Goiânia, 2018.