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| Author(s): |
Luiz Felipe Domingues Passero
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | São Paulo. |
| Institution: | Universidade de São Paulo (USP). Faculdade de Medicina (FM/SBD) |
| Defense date: | 2011-06-09 |
| Examining board members: |
Marcia Dalastra Laurenti;
Francisco Javier Hernandez Blazquez;
Sandra do Lago Moraes;
Daniela Santoro Rosa;
Fernando Tobias Silveira
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| Advisor: | Marcia Dalastra Laurenti |
| Abstract | |
Leishmania (Viannia) shawi specie was recently characterized by Lainson group. Currently, studies indicate important medical and epidemiological role of this parasite in Brazil. Therefore, the aims of this study were to characterize the experimental murine model of this infection, purify proteic antigens and evaluate their protection degrees after challenge. To characterize the murine model of infection, BALB/c and C57BL/6 mice were infected in the footpad with promastigote forms, and the histopathological and immunological findings were evaluated during the evolution of infection. For the immunization studies, 10 different antigens were used, as follow: three released/excreted by promastigote forms of L. (V.) shawi; two intracellular soluble antigens from amastigote (AgAma) and promastigote forms (AgPro), and 5 proteic fractions purified from soluble intracellular antigens from promastigote forms. These antigens have been used to immunize BALB/c mice twice, subcutaneously in the rump. After 1 week of last immunization, the animals were challenged. The lesion developments in animals were followed during either six or eight weeks post-challenge (PC), when the animals were sacrificed to evaluate the parasite load and aspects of cellular and humoral immune responses. BALB/c mice were the most susceptible to L. (V.) shawi infection, since the histopathological and humoral changes were higher in BALB/c than C57BL/6 mice. Secreted/excreted antigens of low molecular mass induced high protection rate compared to non-immunized mice, already mice immunized with secreted/released antigens of medium molecular mass showed mild protection, possibly caused by high expression of IFN-g and IL-4 by CD8+ T lymphocytes. AgAma and AgPro showed antagonic response in animals, since AgAma suppressed the IFN-g and IL-12 production, however high level of TGF-b has been detected, allowing the increasing of parasitism in the skin and lymph nodes. In spite of the detection of TGF-b in AgPro-immunized mice, there was a balance in the cytokines production, with the participation of IFN-g and IL-12, leading to parasite control in skin. Through the purification of AgPro, it was observed a protective effect of F1 and F5 antigens in the skin after challenge; in addition, F1 also protected the lymph nodes of BALB/c mice. Both F3 and F4 antigens exacerbated the skin infection. The identification, by mass spectrometry, revealed that F1 was composed by 67 components, and the majority has not been identified till now. Moreover, F1 induced long-lasting immunity in BALB/c mice, associated to generation of memory CD8+ T lymphocytes, however low parasitism could be the reflect of high production of IL-10. These data indicate which F1 antigen could be an important vaccine candidate against American Tegumentar Leishmaniasis (AU) | |