Publicação
Determining the mechanism of inhibition of TLR3 by I329L ASFV protein
| Resumo: | The African Swine Fever Virus (ASFV) is a cytoplasmically replicating DNA virus transmitted by ticks, which causes a highly contagious and frequently fatal disease in domestic pigs. ASFV pathogenesis is typified by extensive haemorrhage and lymphoid apoptosis, with an associated tropism for macrophages. Viral spread is inhibited through the impact of interferon secreted from the early infected cells, which stimulates the expression of interferon stimulated genes (ISGs) that confer the development of an anti-viral state to resist viral replication in both infected and nearby non-infected cells. In order to survive in macrophages, the ASFV must have evolved multiple genes for evasion and manipulation of interferon. Toll-like Receptors (TLRs) are particularly important in the induction of the innate immune response. This, and the fact that the virus is adapted to survive in both vertebrate and invertebrate hosts, with only innate immunity being common to both, stimulated us to search for and identify a TLR antagonist in the ASFV genome, I329L. The ASFV I329L ORF was interestingly predicted to be a type I transmembrane protein containing two leucine-rich repeats (LRRs) in its extracellular domain and a barely detectable homology with the TLR3 intracellular TIR domain, raising the possibility that I329L might inhibit activation of IFN-β through an inhibitory interaction with the TIR motif of the TLRs and the corresponding downstream signaling adaptor proteins. This structural homology correlated with luciferase reporter assays which clearly demonstrated that I329L inhibits TLR3-mediated activation of NF-kB and IRF3, therefore inhibiting production of IFN-β. Thus, this work attempted to clarify the mechanisms by which I329L is able to inhibit the TLR3 signalling pathways. We have determined that I329L has evolved two distinct strategies for inhibition of TLR3: the extracellular domain interferes with dimerization of TLR3 and other TLRs, perhaps through the formation of non-signaling heterodimers, while the intracellular domain directly interacts with TRIF (a signaling protein downstream of TLR3), inhibiting signal transmission. |
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| Autores principais: | Moura, Pedro Luís Vaz Belo, 1992- |
| Assunto: | Peste suína africana Vírus - peste suína africana Interferão Teses de mestrado - 2015 |
| Ano: | 2015 |
| País: | Portugal |
| Tipo de documento: | dissertação de mestrado |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade de Lisboa |
| Idioma: | inglês |
| Origem: | Repositório da Universidade de Lisboa |
| Resumo: | The African Swine Fever Virus (ASFV) is a cytoplasmically replicating DNA virus transmitted by ticks, which causes a highly contagious and frequently fatal disease in domestic pigs. ASFV pathogenesis is typified by extensive haemorrhage and lymphoid apoptosis, with an associated tropism for macrophages. Viral spread is inhibited through the impact of interferon secreted from the early infected cells, which stimulates the expression of interferon stimulated genes (ISGs) that confer the development of an anti-viral state to resist viral replication in both infected and nearby non-infected cells. In order to survive in macrophages, the ASFV must have evolved multiple genes for evasion and manipulation of interferon. Toll-like Receptors (TLRs) are particularly important in the induction of the innate immune response. This, and the fact that the virus is adapted to survive in both vertebrate and invertebrate hosts, with only innate immunity being common to both, stimulated us to search for and identify a TLR antagonist in the ASFV genome, I329L. The ASFV I329L ORF was interestingly predicted to be a type I transmembrane protein containing two leucine-rich repeats (LRRs) in its extracellular domain and a barely detectable homology with the TLR3 intracellular TIR domain, raising the possibility that I329L might inhibit activation of IFN-β through an inhibitory interaction with the TIR motif of the TLRs and the corresponding downstream signaling adaptor proteins. This structural homology correlated with luciferase reporter assays which clearly demonstrated that I329L inhibits TLR3-mediated activation of NF-kB and IRF3, therefore inhibiting production of IFN-β. Thus, this work attempted to clarify the mechanisms by which I329L is able to inhibit the TLR3 signalling pathways. We have determined that I329L has evolved two distinct strategies for inhibition of TLR3: the extracellular domain interferes with dimerization of TLR3 and other TLRs, perhaps through the formation of non-signaling heterodimers, while the intracellular domain directly interacts with TRIF (a signaling protein downstream of TLR3), inhibiting signal transmission. |
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