O papel do receptor do tipo Toll 6 na resposta imune contra a infecção pela bactéria Mycobacterium avium

Exportado OPUSMade available in DSpace on 2019-08-13T03:56:44Z (GMT). No. of bitstreams: 1 tese_f_bio_marinho_2013.pdf: 3293155 bytes, checksum: c5ee90c77b5079e94c8a88249ef4be29 (MD5) Previous issue date: 19A resposta imune inata corresponde à primeira linha de defesa contra as infecções, onde os receptores do tipo Toll (TLRs) são importantes no reconhecimento de patógenos. A ativação de TLRs leva à produção de citocinas e outros mecanismos necessários ao controle eficiente de infecções. O Mycobacterium avium é um importante patógeno oportunista que infecta principalmente indivíduos imunocomprometidos. No presente trabalho foi avaliada a participação do receptor TLR6 no reconhecimento e controle da infecção pelo M. avium. O ensaio de luciferase e transfecção de TLRs em células HEK 293 mostrou o TLR6 age sinergicamente com o TLR2 no reconhecimento do M. avium e na ativação de NF-_B. Corroborando com esse dado, a infecção por M. avium leva ao aumento da expressão de TLR6 e TLR2 em macrófagos (BMMs) e células dendríticas (BMDCs) murinos derivados da medula óssea. Além disso, a deficiência em TLR6 reduz a produção de TNF-_, IL-12 e IL-6 em BMDCs e aumenta a susceptibilidade de BMMs à infecção pelo patógeno. A investigação das vias de sinalização intracelular revelou que a fosforilação de JNK, ERK1/2 e p38 é dependente deste receptor em ambos os tipos celulares estimuladas com M. avium. É interessante ressaltar que neste sistema MyD88, TLR6 e TLR2 influenciam significativamente a ativação de NF-_B em células dendríticas, apesar de serem apenas parcialmente relevantes em macrófagos. As análises in vivo demonstraram que camundongos deficientes para TLR6 infectados pelo patógeno apresentam maior carga bacteriana no baço, fígado e pulmões do que os animais selvagens, indicando que este receptor é necessário ao controle eficiente desta infecção. No entanto, o TLR6 não está envolvido na produção de IFN-_ ou TNF-_ por esplenócitos. De fato, o nível dessas citocinas estava alterado apenas em camundongos MyD88 KO. Além disso, a análise por citometria de fluxo revelou que apenas a deficiência em MyD88 reduziu a porcentagem de linfócitos T CD4+ ou CD8+ produtores de IFN-_ no baço. O nível dessa citocina medido diretamente no tecido pulmonar estava significativamente reduzido em animais TLR6 ou TLR2 KO comparados aos camundongos selvagens. Por outro lado, a área dos granulomas observados no fígado estava reduzida somente em camundongos MyD88 KO. Ademais, o bloqueio de TLR6 em células da linhagem monocítica humana THP-1 estimuladas por M. avium reduziu a produção de TNF-_ e a ativação de MAPKs, indicando que os dados observados em camundongos podem ser extrapolados para seres humanos.The innate immune response corresponds to the first line defense against infections, with the Toll-like receptors (TLRs) being important to pathogen recognition. The activation of TLRs leads to the production of cytokines and other immune mechanisms necessary to the efficient control of infections. The Mycobacterium avium is an important opportunistic pathogen that infects principally immunocompromised individuals. In the present study we evaluated the participation of TLR6 in the recognition and control of M. avium infection. The luciferase assay in HEK 293 cells showed that TLR6 acts synergistically with TLR2 and they are important for M. avium recognition. Supporting this result, M. avium infection leads to a higher expression of TLR6 and TLR2 in mice bone marrow derived macrophages (BMMs) and dendritic cells (BMDCs). Moreover, TLR6-deficiency reduces the production of TNF-_, IL-12 and IL-6 in BMDCs and increases the susceptibility of BMMs to infection. Analysis of the intracellular signaling pathways revealed that phosphorilation of JNK, ERK1/2 and p38 is dependent on TLR6 in both cell types stimulated with M. avium. Additionally, MyD88, TLR6 and TLR2 influence the activation of NF-_B in dendritic cells, although these receptors are only partially relevant in macrophages. The in vivo analysis demonstrated that TLR6-defficient mice infected with M. avium showed a higher bacterial burden in spleen, liver and lungs compared to wild type animals, indicating that this receptor is necessary for the efficient control of this infection. However, TLR6 is not involved in the production of IFN-_ or TNF-_ by splenocytes. The level of these cytokines was altered only in MyD88 KO mice. In parallel with this finding, the flow cytometry analysis demonstrated that only in MyD88-defficient mice the percentage of CD4+ or CD8+ T lymphocytes producing IFN-_ in spleen was reduced. In contrast, IFN- _ level was significantly lower in TLR6 or TLR2 KO mouse lungs, when compared to 9 wild type animals. Nevertheless, the liver granuloma area was found to be reduced only in MyD88 KO mice. Finally, blocking of TLR6 in THP-1 human monocytic cell line infected with M. avium reduced the production of TNF-_ and activation of MAPKs, indicating that the mouse findings observed here be extrapolated to humans

Peptides containing T cell epitopes, derived from Sm14, but not from paramyosin, induce a Th1 type of immune response, reduction in liver pathology and partial protection against Schistosoma mansoni infection in mice

Sm14 and paramyosin are two major Schistosoma mansoni vaccine candidate antigens. Recently, we have identified Sm14 and paramyosin epitopes that are recognized by T cells of resistant individuals living in endemic areas for schistosomiasis. Herein, mice were immunized with these peptides separately or in association in order to evaluate their vaccine potential. Immunization of mice with Sm14 peptides alone or mixed with paramyosin peptides was able to induce 26%-36.7% or 28%-29.2% of worm burden reduction, 67% or 46% of intestinal eggs reduction and also 54%-61% or 43%-52% of liver pathology reduction, respectively. Protection was associated with a Th1 type of immune response induced by Sm14 peptide immunization. In contrast, paramyosin peptide vaccination did not engender protective immunity or liver pathology reduction and immunization was associated with a Th2 type of immune response. (C) 2008 Elsevier B.V. All rights reserved