Novo antígeno recombinante para diagnóstico sorológico da tripanossomose bovina

• Ano de defesa: 2018
• Autor(a) principal: Guilherme Rafael Gomide Pinheiro
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Minas Gerais; UFMG
• Palavras-chave em Português: sorodiagnóstico; Tripanossomose bovina; Gênero Trypanosoma; antígeno recombinante; Ciência animal
• Link de acesso: http://hdl.handle.net/1843/SMOC-AXAPK2

Trypanosomes are parasitic infections of humans and animals, caused by protozoa of the genus Trypanosoma. Bovine trypanosomiasis (BT) is caused by the protozoa T. vivax, T. congolense and T. brucei. BT acute infections are characterized initially by hyperthermia, followed by moderate to severe anemia, subcutaneous edema, lethargy, reduced milk production, progressive weight loss, enlarged lymph nodes and reproductive disorders. The chronic phase occurs in those animals that survive the acute phase and begin to recover of infection becoming asymptomatic. Direct parasitological examination (Woo technique or blood smears) is the diagnostic method used routinely by veterinarians as it is a quick and inexpensive method. However, the low sensitivity of this technique limits its use in epidemiological studies, since chronically infected animals present low parasitemia and are considered the main reservoirs of these protozoa. Serological techniques using crude antigen have often been used in epidemiological studies of BT, and based on the immunological status of the animals it is possible to determine the epidemiological situation in different regions in which such parasitoses take place. The objective of this study was to develop more specific and sensitive serological diagnostic tools for the diagnosis of bovine trypanosomiasis. For this, a gene conserved among trypanosomatids (MyxoTLm) was expressed in a heterologous system by using pET28a-TEV plasmid as vector and Escherichia coli BL21 Star strain as expression system. The expressed protein was purified by affinity chromatography and used as antigen in an ELISA test. Indirect anti-IgM and anti-IgG ELISAs assembled with the recombinant antigen showed high discriminatory power when sera from healthy (negative control) and diseased (BT) animals were tested as they reached 91.30% and 95.65% specificity, and 82.35% and 88.23% sensitivity, respectively. In addition, recombinant protein demonstrated a good performance to detect IgM, with the area under the ROC curve of 0.8568, and excellent performance to detect IgG, with area under the ROC curve of 0.9565. The crude antigen used in the indirect anti-IgM ELISA reached 70.58% sensitivity and 78.26% specificity, and presented low test performance, with area under the ROC curve of 0.7363. When applied to the anti-IgG indirect ELISA, the crude antigen reached 82.35% sensitivity and 69.56% specificity, also presenting a low performance with area under the ROC curve of 0.7570. Therefore, the recombinant protein used in this study is promissory to be applied in the immunodiagnosis and demonstrated great potential to be utilized in BT serological diagnosis.