Diagnóstico imunológico da cisticercose bovina utilizando antígenos de taenia crassiceps: avaliação de protocolos laboratoriais

• Autor(a) principal: Silva, Letícia Ferreira da
• Data de Publicação: 2013
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/5138
• topic: Cisticercose bovina; Padronização; Diagnóstico imunológico; Bovine cysticercosis; Standardization; Immunological diagnosis; CNPQ::CIENCIAS AGRARIAS::MEDICINA VETERINARIA::INSPECAO DE PRODUTOS DE ORIGEM ANIMAL

The bovine cysticercosis, caused by the larval form of Taenia saginata, is a current problem in Brazilian beef cattle, determining economic losses to the meat industry due to the carcass condemnation, also represents risks to public health. The main control measure of this zoonosis is applied after post-mortem examination at meat inspection; however, this method fails in detecting cysticerci in cases of low infections, reinforcing the need for additional research to develop alternatives for diagnosis, such as serological tests. The objectives of this study were: to evaluate different laboratory protocols of ELISA for the diagnosis of bovine cysticercosis using Taenia crassiceps (Tcra) larvae antigens to assess their performance against different categories of control sera from slaughtered cattle and, through immunoblotting, to identify peptides with significant diagnostic potential for bovine cysticercosis. Serum samples of cattle experimentally infected with eggs of T. saginata and negative for cysticercosis were also used in the evaluation of different laboratory protocols of ELISA, which involved six antigens of Tcra: total (T), total sonicated (Ts), total dialysate (Td), membrane (M), vesicular fluid (VF) and sonicated vesicular fluid (sVF). From previously defined protocols, we evaluated the performance of ELISA in a final step with the antigens T, Ts and M against sera of positive bovines (experimental and natural) and negative for cysticercosis, and of bovine with other pathologies. The immunoblotting assays were conducted with the T antigen, using four groups of control sera and then reactive peptides were identified and their frequencies and performance ratios were set. With previous evaluation of the protocols we have defined antigen concentrations of 10 μg/ml for VF and sVF antigens and 40 μg/ml for T, Ts, Td and M antigens; the established conjugate dilutions were 1:1.250 ( T, Ts and M) and 1:2,500 (Td, VF and sVF); the best serum dilution tested was 1:100 and the best blocking substance was 5% skimmed milk powder; and the antigens that best differed positive and negative animals were M and T antigens, followed by Ts and Td. The sensitivity rates obtained by ELISA were, respectively, with 2 and 3 standard deviations, 85 and 81.25% for T antigen, 82.5 and 78.75% for Ts antigen, and 80 and 80% for M antigen; specificity rates, with 2 and 3 standard deviations, were, respectively: 47.5 and 58.75% for T antigen, 65 and 73.75% for Ts antigen, and 58.75 and 62.5% for M antigen. In the immunoblotting, the most important diagnostical peptides, in descending order of accuracy were: 6-8 kDa (90.8%), 129-143 kDa (74.2%), 99-105 kDa (71.7%) and 14-19 kDa (71.1%). The suitable combination of various tested parameters contributed to increase the reliability of the ELISA test, once it facilitates the distinction between positive and negative animals. These protocols provided high sensitivity rates, which enables the practical applicability of the test, because it complements the post-mortem examination that shows high specificity, but low sensitivity in detecting carcasses with discrete infections. The results obtained by immunoblotting showed that the T antigen has peptides with a high diagnostic potential; hence, another serological test is useful in the diagnosis of bovine cysticercosis.