Resposta imunológica induzida pelas vacinas de Brucella abortus B19 e RB51 em bezerras: efeitos da idade a vacinação

Abstract

Brucellosis is one of the main zoonoses in public and animal health and in economic significance in the world. Cattle are the preferred hosts of Brucella abortus and, in sexually mature animals, the infection is established in the reproductive system, typically producing placentitis followed by abortion in pregnant females during the last trimester of pregnancy and epididymitis and orchitis in males. The main mechanism for controlling the disease is through the compulsory vaccination of cattle and buffaloes. The most used vaccines to control brucellosis are S19 and RB51. The animals are vaccinated, mainly with S19, between 3 and 8 months of age, but there is no consensus on the best age, within this range, to stimulate the immune response and the generation of memory cells in heifers. Thus, the aim of this study is to evaluate the best age for vaccination against bovine brucellosis in calves from 3 to 8 months of age. For this, 105 animals were used and subdivided into 9 groups, 3 vaccinated with B19, 3 with RB51 and 3 controls, with ages ranging from 3-4, 5-6 and 7-8 months in each group. After vaccination on day 0, assays to assess the immunological response induced by vaccination were performed on the 28th and 56th day after vaccination, which were: culture supernatant ELISA to assess IFN-γ production; Standard agglutination test by tube and 2-mercaptoethanol, to verify the seroconversion of animals vaccinated with S19; I-ELISA for IgG measurement. In direct ELISA, differences in IFN γ production were observed on days 28 and 56, when treatments were compared (S19, RB51 and control) for the same age. The results of 2ME and STAT also showed that all animals vaccinated with S19 were seroconverted on day 28, while the rest remained negative. In the I-ELISA test, the mean optical density (OD) in vaccinated animals is higher. The study results indicate that calves vaccinated with S19 or RB51 older than 5 months (5-8 months) have earlier IFN-γ production, suggesting that this is the best age to vaccinate animals.