Caracterização morfológica, genética, parasitológica e imunopatológica de um isolado de Schistosoma mansoni obtido do roedor silvestre Holochilus sciureus

• Ano de defesa: 2022
• Autor(a) principal: Guilherme Silva Miranda
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Minas Gerais; Brasil; ICB - DEPARTAMENTO DE PARASITOLOGIA; Programa de Pós-Graduação em Parasitologia; UFMG
• Palavras-chave em Português: Esquistossomose; Holochilus sciureus; Morbidade; Resposta imune; Caracterização genética; Reservatório silvestre; Biomphalaria glabrata; Parasitologia; Roedores; Perfil Genético; Biomphalaria
• Link de acesso: http://hdl.handle.net/1843/51279; https://orcid.org/ 0000-0003-3763-2776

Schistosoma mansoni is the etiologic agent of schistosomiasis, a parasitic disease associated with high rates of mortality and morbidity in humans. In addition to humans, some species of wild rodents are also susceptible to this parasite and successive infections in these animals may favor the selection of new strains of S. mansoni, whose impact on morbidity, transmission, and control of schistosomiasis is still unknown. Thus, this work aimed to describe the isolation process of S. mansoni obtained from naturally infected Holochilus sciureus rodents (HS strain), captured in Maranhão, Brazil. Subsequently, the present study comparatively evaluated morphological and genetic aspects of the isolated parasite, in addition to the parasitic kinetics and immunopathological response induced by the HS and the LE strain (originally isolated from humans) during experimental infections in BALB/c mice and Biomphalaria glabrata snails. To isolate the parasite, miracidia obtained from livers of H. sciureus were used to infect sympatric (SB) and allopatric (BH) strains of B. glabrata, and the cercariae produced were used to infect hamsters and/or BALB/c mice experimentally. After isolation, the parasitological profile of the HS strain infection in these hosts was evaluated and the 16S and cox 1 genetic regions of worms obtained from these experimental models were amplified and sequenced. Subsequently, new infections were performed in mice and B. glabrata, using the HS and the LE strain of S. mansoni for the comparative evaluation of morphometric aspects of eggs eliminated in feces, miracidia, cercariae, and adult worms. To assess the parasitological and immunopathological profile of S. mansoni HS strain infection in vertebrate hosts, groups of BALB/c mice were infected with 50 cercariae of HS or LE strain, and these animals were comparatively evaluated during acute and chronic experimental schistosomiasis. Finally, to investigate the interaction between B. glabrata and the HS strain of S. mansoni, groups of snails infected with 15 miracidia of the HS or LE strains were comparatively evaluated during 91 dpi. Our isolation attempts demonstrated that only miracidia obtained from infected mice, but not from hamsters, were able to infect B. glabrata, allowing the maintenance of the parasite in the laboratory. The sequences showed 100% similarity with S. mansoni, and the phylogenetic analysis demonstrated that the HS strain of the parasite forms a group with isolates from Brazil, Puerto Rico, Guadeloupe, and Kenya. Despite this genetic similarity with other S. mansoni isolates, the HS strain had biological peculiarities: experimental infection of B. glabrata SB with S. mansoni HS resulted in two peaks of cercariae shedding, at 45 and after 70 days post-infection (dpi), and the worm recovery rate in mice was very low, about of 13%. In addition, our comparative morphological evaluations showed that HS miracidia had smaller body dimensions; however, HS cercariae were larger than those of the LE strain. Additionally, adult male worms of the HS strain have a greater number of tegumental tubercles and the female worms have a smaller area of the spermatheca and a higher frequency of eggs in the ootype, compared to the LE strain. In BALB/c mice, we showed that the infection by the HS strain had a lower parasite burden; however, the HS females showed higher fecundity when compared to the LE strain. Moreover, mice infected with the HS strain showed reduced concentrations of IL-5, IL-10, and IL-13, and lower EPO activity in liver homogenate; but higher concentrations of TNF-α, IFN-γ, IL-12, and IL-17 in the small intestine homogenate, compared to the LE strain. S. mansoni HS strain infection also resulted in higher concentrations of NO end-products in tissues and induced an increase in plasma transaminase levels, formation of larger granulomas, and a higher mortality rate. In B. glabrata snails, we demonstrated that the infection by the HS strain had a higher rate of infection and a delay in secondary sporocyst migration (30–40 dpi) and cercariae shedding (77 dpi.), compared to the LE strain. In addition, B. glabrata infected with the HS strain did not significantly change the number of circulating hemocytes compared to uninfected snails, resulting in a smaller number of cells compared to snails infected with the LE strain, at 15 dpi. Infection by the HS strain also resulted in a reduction in the concentration of proteins homologous to humans in the hemolymph, such as TNF-α and IL-17, and an increase in H2O2, myeloperoxidase, and arginase in the tissue. Thus, our data demonstrate that BALB/c mice and B. glabrata snails support the maintenance of S. mansoni isolated from H. sciureus under laboratory conditions. Based on this knowledge, it was possible to characterize the genetic profile of the HS strain and demonstrate that this parasite strain has distinct morphological characteristics and differentiated parasitological and immunopathological patterns in vertebrate and invertebrate hosts, which may favor its transmission and induce greater severity of schistosomiasis.