Submitted by Jorge Silva (jorgelmsilva@ufrrj.br) on 2017-06-06T18:14:40Z No. of bitstreams: 1 2015 - Vin?cius Menezes Tunholi Alves.pdf: 1609397 bytes, checksum: 1c31fd547893728f1c9c9165ee10137c (MD5) / Made available in DSpace on 2017-06-06T18:14:40Z (GMT). No. of bitstreams: 1 2015 - Vin?cius Menezes Tunholi Alves.pdf: 1609397 bytes, checksum: 1c31fd547893728f1c9c9165ee10137c (MD5) Previous issue date: 2015-07-01 / FAPERJ / Angiostrongylus cantonensis Chen, 1935 was first described as a parasite of the pulmonary artery of Rattus norvegicus and Rattus rattus in Canton, China. This helminth is an etiological agent of eosinophilic meningoencephalitis, a zoonotic disease endemic to certain Asian countries, which has recently dispersed to Africa, North and South America, and Caribbean islands. Currently Brazil is considered an area of high risk for the establishment of human angiostrongyliasis, due mainly to the occurrence of naturally infected snails and rodents, acting respectively as definitive and intermediate hosts of this parasite, directly favoring the transmission dynamics of neural angiostrongyliasis. In its life cycle, snails act as intermediate hosts, allowing the development of infective larval forms in the definitive host. In recent years, the metabolic characteristics of experimentally infected snails have been studied in an effort to develop measures to control the pathologies transmitted by these organisms. However, there is little information on the relationship between A. cantonensis and the freshwater snail Biomphalaria glabrata, which is cause for concern, not only because of the importance of this parasite, but also due to the widespread distribution of this snail in Brazil. In this study, the metabolic alterations of B. glabrata resulting from experimental infection by A. cantonensis were evaluated. For this purpose, snails of the pigmented strain were used, reared in the laboratory since oviposition. Two overall groups were formed: control (C1, C2 and C3), with uninfected animals, and treated (I1, I2 and I3), with infected snails. Each subgroup was composed of 10 snails. The entire experiment was performed in duplicate, utilizing a total of 120 snails. After one, two and three weeks of infection, 20 snails from each group were dissected to collect the hemolymph and tissues. The spectrophotometric readings were performed with Doles commercial reagent kits. The biochemical measurement demonstrated that infection by A. cantonensis induced a significant reduction in the hemolymph concentrations of calcium after one week of infection, followed by an increase in the concentrations of this ion in the second week of infection. This situation was accompanied by intense mobilization of CaCO3 in the shell of the infected snails, possibly as an attempt to reestablish the acid-base equilibrium after its alteration during the parasites? development. The histopathology results also demonstrated morphological changes in the digestive gland of infected snails, mainly in the form of granulomatous reactions and areas of metastatic calcification. Variations in the reserves of neutral lipids stored in the digestive gland-gonad complex were also observed. Infection resulted in a significant decrease in the concentrations of cholesterol and an increase in the levels of fatty acid and triacylglycerol after the first two weeks of infection. The increase in the concentration of fatty acid was associated with an increase in lipase activity, indicating that A. cantonensis induces activation of a lipolytic process during development in its intermediate host. Finally, infection by A. cantonensis resulted in changes in the oxidative metabolism of B. glabrata. Besides depletion of the polysaccharide reserves stored in the digestive gland and cephalopodal mass, parasitism by A. cantonensis induced activation of the host?s anaerobic metabolism, resulting not only in an increase in activity of lactate dehydrogenase in the hemolymph, but also reduction of the levels of pyruvic acid and accumulation of lactate. This is an interesting adaptive response of the host to infection, enabling the host, through anaerobic metabolism, to generate energy while still maintaining its redox balance. Additionally, the reduction in the concentrations of oxalic acid in the final parasite development periods suggests its diversion to gluconeogenesis, indicating the involvement of this molecule as a precursor in the synthesis of glucose-6-phosphate. This metabolic condition was accompanied by a deletion in oxidative phosphorylation infected snails (1 and 2 weeks) after infection, suggesting a decrease in the number of mitochondria in the examined tissue, or suppression of enzymatic centers related to oxidative reactions. / O nemat?ide Angiostrongylus cantonensis foi primeiramente descrito como parasito de art?ria pulmonar de Rattus norvegicus e Rattus rattus em Canton, China. Este helminto tem sido mencionado como principal agente etiol?gico da meningoencefalite eosinof?lica humana, uma metazoonose end?mica no continente asi?tico e que recentemente, tem-se disseminado para ?frica, Norte e Sul da Am?rica e Ilhas do Caribe. Atualmente, o Brasil ? considerado ?rea de alto risco ao estabelecimento da angiostrongil?ase humana, justificado n?o somente pela presen?a de moluscos, mas tamb?m roedores naturalmente infectados, que atuam respectivamente como hospedeiros intermedi?rios e definitivos desse parasito, fatores que favorecem diretamente a din?mica de transmiss?o da angiostrongil?ase neural. Em seu ciclo de vida moluscos atuam como hospedeiros intermedi?rios, possibilitando a partir se sua infec??o, o desenvolvimento de formas larvais infectantes ao hospedeiro definitivo. Nos ?ltimos anos, a caracteriza??o de padr?es metab?licos de moluscos infectados experimentalmente, tem sido estudada como base para o desenvolvimento de medidas focadas principalmente no controle de patologias transmitidas por estes organismos. Por?m, quando nos referimos a modelos experimentais utilizando A. cantonensis e Biomphalaria glabrata, os dados ainda s?o escassos, o que preocupa, n?o apenas pela import?ncia do parasito, mas tamb?m pela ampla distribui??o da esp?cie B. glabrata no Brasil. Neste estudo, foram observadas altera??es no metabolismo mineral, lip?dico e oxidativo de B. glabrata, decorrentes da infec??o experimental por A. cantonensis. Para isso, foram utilizados moluscos da linhagem pigmentada criados desde a oviposi??o e mantidos em condi??es laborat?riais. Foram formados dois grupos: controle (C1, C2, C3) com animais n?o infectados e infectados (I1, I2 e I3). Os grupos eram compostos por 10 moluscos. Todo experimento foi feito em duplicata, utilizando um total de 120 moluscos. Ap?s 1, 2 e 3 semanas de infec??o, 20 moluscos de cada grupo eram dissecados para a coleta da hemolinfa e tecidos. As leituras espectrofotom?tricas foram realizadas a partir de kits comercias da marca Doles. As dosagens bioqu?micas demonstraram que a infec??o por A. cantonensis induziu uma diminui??o significativa nos conte?dos hemolinf?ticos de c?lcio ap?s primeira semana de infec??o, seguido por um aumento nas concentra??es desse ?on na segunda semana de estudo. Este cen?rio foi acompanhado por uma intensa mobiliza??o de CaCO3 na concha de moluscos infectados, possivelmente como tentativa em restabelecer o equil?brio ?cido-base alterado durante o desenvolvimento do parasito. Resultados histopatol?gicos demonstraram ainda altera??es morfol?gicas na gl?ndula digestiva de moluscos infectados, caracterizadas principalmente na forma de rea??es granulomatosas e ?reas de calcifica??o metast?tica. Varia??es nas reservas de lip?dios neutros estocados no complexo gl?ndula digestiva-g?noda foram tamb?m demonstradas. A infec??o resultou em um decr?scimo significativo nos conte?dos de colesterol e no aumento dos n?veis de ?cido graxo e triacilglicerol ap?s as duas primeiras semanas de infec??o. O aumento nos conte?dos de ?cido graxo foi associado ao aumento da atividade lip?sica, indicando que A. cantonensis induz de fato a ativa??o de um processo lipol?tico durante etapa de desenvolvimento em seu hospedeiro intermedi?rio. Por fim, a infec??o de A. cantonensis resultou em mudan?as no metabolismo oxidativo de B. glabrata. Al?m da deple??o de reservas polissacar?dicas estocadas na gl?ndula digestiva e massa cefalopodal, o parasitismo por A. cantonensis induziu a ativa??o do metabolismo anaer?bio de seu hospedeiro, resultando n?o apenas no aumento da atividade da lactato desidrogenase hemolinf?tica, mas tamb?m na redu??o dos n?veis de ?cido pir?vico e ac?mulo de lactato. Isso representa uma interessante resposta adaptativa do hospedeiro frente ? infec??o, possibilitando o hospedeiro a partir do metabolismo anaer?bio, gerar energia e ao mesmo tempo mant?m seu balan?o redox. Adicionalmente, a redu??o nas concentra??es de ?cido ox?lico observado nos per?odos finais do desenvolvimento parasit?rio, sugere o seu desvio para a gliconeog?nese, destacando o envolvimento dessa mol?cula como precursora na s?ntese de glicose-6-fosfato. Este cen?rio metab?lico foi acompanhado por uma supress?o na fosforila??o oxidativa de moluscos infectados (1 e 2 semanas) de infec??o, sugerindo uma diminui??o na quantidade de mitoc?ndrias no tecido analisado, ou ainda, na inibi??o de centros enzim?ticos relacionados ?s rea??es oxidativas.

L'étude des interactions hôtes/parasites est actuellement un thème de recherche incontournable des sciences de l'évolution. Une des questions majeures soulevée par ces études est de comprendre pourquoi certains parasites provoquent des maladies mortelles, alors que d'autres restent relativement bénins pour leurs hôtes. Dans ce défi que tentent de relever les biologistes de l’évolution mais également les sciences médicales, nous avons choisi de nous intéresser à la malaria aviaire, et plus précisément à son représentant le plus commun dans les populations naturelles d’oiseaux : Plasmodium relictum. En procédant à des infections expérimentales de canaris domestiques (Serinus canaria), nous avons voulu comprendre quels facteurs liés aux caractéristiques du parasite et de l’oiseau (au niveau de l’individu ou de la population) pouvaient influencer la virulence de Plasmodium relictum. Nous avons ainsi pu mettre en évidence que des facteurs, tels que le passé infectieux de l’hôte, la dose de parasites reçue, la prévalence de ces derniers dans la population d’oiseaux ou bien encore les interactions sociales entre individus, pouvaient moduler les coûts d’une telle infection. La virulence est un trait composite qui dépend, certes, de l’exploitation de l’hôte par les parasites mais également de la réponse immunitaire de ce dernier contre l’infection. Nous avons pu le vérifier dans notre système expérimental en utilisant une approche immuno-écologique. Nous nous sommes enfin intéressée aux conditions favorisant l’évolution de la virulence : ce qui est essentiel pour comprendre l’émergence ou la réémergence de maladies infectieuses et pour développer des stratégies de contrôle de ces maladies. / Host-parasite interaction became one of the main topics of evolutionary sciences researches. One of the major issues raised by these studies is to understand why some parasites cause fatal diseases while others remain relatively mild to their hosts. In this challenge attempting to take up the evolutionary biologist and the medical sciences, we focused on avian malaria, and more specifically on its most common parasite: Plasmodium relictum. In performing experimental infections in domestic canaries (Serinus canaria), we wanted to understand what factors related to parasite and birds characteristics, could influence Plasmodium relictum virulence. We highlighted that factors such as infectious past, parasites dose, prevalence in bird’s population and social interactions between individuals could modulate costs of such infection. Virulence is a composite trait that depends on the host’s exploitation by parasites but also the host’s immune response against the infection. We were able to show that in our experimental system using an approach of immunological ecology. Finally we focused on the conditions favouring the virulence evolution: an essential point to understand emergence or re-emergence of infectious diseases and to develop strategies to control these diseases.