Caracterização de respostas imunes locais associadas ao fenótipo de resistência parasitária em cordeiros da raça Morada Nova
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Data
2019-04-12
Autores
Toscano, João Henrique Barbosa
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
Tendo em vista o impacto da infecção por Haemonchus contortus na ovinocultura, é crescente o número de estudos acerca da resistência a esse parasita, sendo essencial a compreensão dos mecanismos imunes diretamente relacionados. A resposta a infecções por helmintos é predominantemente de perfil Th2, embora o conjunto de mecanismos imunes que conferem resistência aos ovinos não sejam completamente elucidado. O presente estudo objetivou avaliar as respostas imunes locais (abomaso) associados à resistência à infecção por H. contortus em cordeiros Morada Nova, raça considerada resistente. Um rebanho composto por 287 ovinos foi fenotipado, por meio de contagens de ovos nas fezes, volume globular e peso corporal, após dois desafios parasitários com 4000 L3. Os 20 extremos de infecção (10 mais resistentes e 10 mais susceptíveis) foram submetidos a um terceiro desafio e abatidos sete dias após. Foram quantificados, por RT-qPCR, os níveis de expressão de 22 genes associados às respostas imunes, em abomaso e linfonodos abomasais. Além disso, eosinófilos e mastócitos foram quantificados, e os níveis de IgG e IgA no muco abomasal mensurados. Genes relacionados à resposta inata (TLR2 e CFI) foram superiormente expressos na região pilórica dos animais resistentes. Esses animais também apresentaram, na região fúndica, IL33 (promotor da polarização Th2) e MS4A2 (receptor de IgE) em níveis superiores aos verificados nos susceptíveis. Marcadores pró-inflamatórios (TNFα e IL1β) foram superiormente expressos na região fúndica do abomaso dos animais susceptíveis. IL4 (resposta Th2) foi superiormente expressa nos linfonodos abomasais dos animais susceptíveis. Os cordeiros resistentes apresentaram maior quantidade de eosinófilos na região fúndica do abomaso e níveis superiores de IgA local. Como esperado, animais susceptíveis apresentaram resposta inflamatória exacerbada, enquanto que os resistentes apresentaram resposta mediada por eosinófilos e IgE. Além disso, os resultados evidenciaram importância da resposta inata na resistência desses cordeiros à infecção por H. contortus, mediada por TLR2 e sistema complemento. Não obstante, esse é o primeiro estudo a associar, diretamente, o fenótipo de resistência parasitária em animais de produção com altos níveis de IL33.
Considering the impact of Haemonchus contortus infection on sheep breeding, there is an increasing number of studies addressing host resistance against to this parasite, and the understanding of directly related immune mechanisms is essential. The response to helminth infections is predominantly Th2- polarized, although the immune mechanisms that confer resistance to sheep are not fully elucidated. The present study aimed to evaluate the local immune responses (abomasum) associated with resistance to H. contortus infection in Morada Nova lambs, a breed considered resistant. A 287 sheep flock was phenotyped, by means of fecal egg counts, packed cell volume and body weight, after two parasitic challenges with 4000 L3. The 20 extremes of infection (10 most resistant and 10 most susceptible) were submitted to a third challenge and slaughtered seven days later. 22 immune-related genes were quantified (RT-qPCR) in abomasum and abomasal lymph nodes. In addition, abomasal eosinophils and mast cells were quantified, and IgG and IgA levels were measured (ELISA) in abomasal mucus. Genes related to innate response (TLR2 and CFI) were superiorly expressed in the pyloric region of the resistant animals. IL33 (Th2 polarization promoter) and MS4A2 (IgE receptor) were also at higher levels in this group. Proinflammatory cytokines (TNFα and IL1β) were superiorly expressed in the fundic region of the susceptible group, which also had IL4 (Th2 response) superiorly expressed in their abomasal lymph nodes. Resistant lambs had higher eosinophils counts in abomasal fundic region, and higher levels of local IgA. As expected, susceptible animals had an exacerbated inflammatory response, whereas the resistant ones had a response mediated by eosinophils and IgE. In addition, the results evidenced importance of the innate response in sheep resistance against H. contortus infection, mediated by TLR2 and complement system. Nevertheless, this is the first study to directly associate the parasite resistance phenotype in production animals with higher levels of IL33.
Considering the impact of Haemonchus contortus infection on sheep breeding, there is an increasing number of studies addressing host resistance against to this parasite, and the understanding of directly related immune mechanisms is essential. The response to helminth infections is predominantly Th2- polarized, although the immune mechanisms that confer resistance to sheep are not fully elucidated. The present study aimed to evaluate the local immune responses (abomasum) associated with resistance to H. contortus infection in Morada Nova lambs, a breed considered resistant. A 287 sheep flock was phenotyped, by means of fecal egg counts, packed cell volume and body weight, after two parasitic challenges with 4000 L3. The 20 extremes of infection (10 most resistant and 10 most susceptible) were submitted to a third challenge and slaughtered seven days later. 22 immune-related genes were quantified (RT-qPCR) in abomasum and abomasal lymph nodes. In addition, abomasal eosinophils and mast cells were quantified, and IgG and IgA levels were measured (ELISA) in abomasal mucus. Genes related to innate response (TLR2 and CFI) were superiorly expressed in the pyloric region of the resistant animals. IL33 (Th2 polarization promoter) and MS4A2 (IgE receptor) were also at higher levels in this group. Proinflammatory cytokines (TNFα and IL1β) were superiorly expressed in the fundic region of the susceptible group, which also had IL4 (Th2 response) superiorly expressed in their abomasal lymph nodes. Resistant lambs had higher eosinophils counts in abomasal fundic region, and higher levels of local IgA. As expected, susceptible animals had an exacerbated inflammatory response, whereas the resistant ones had a response mediated by eosinophils and IgE. In addition, the results evidenced importance of the innate response in sheep resistance against H. contortus infection, mediated by TLR2 and complement system. Nevertheless, this is the first study to directly associate the parasite resistance phenotype in production animals with higher levels of IL33.
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Palavras-chave
Haemonchus contortus, Raça Morada Nova, Resistência do hospedeiro, Resposta imune local