Robson Bahia

Evaluation of the humoral and cellular immune response to different antigens of Corynebacterium pseudotuberculosis in Caninde´ goats and their potential protection against caseous lymphadenitis

Corynebacterium pseudotuberculosis is the etiologic agent of caseous lymphadenitis, a disease that affects goats and sheep, and can cause severe economic losses. In this study, four different antigenic extracts were obtained from the attenuated strain T1, which was isolated in the state of Bahia (Brazil). Forty-four Canindé breed goats were divided in five groups, each receiving a different antigen solution and saline buffer as a control. The humoral response was monitored through the identification of specific IgG by indirect ELISA and Western Blotting, and the production of IFN-gamma was followed in order to observe the activation of cellular response. After twelve weeks of antigen inoculation, the animals were challenged with 2 x 10(5)CFU of a wild strain, also isolated in Bahia, and necropsy was performed on all animals twelve weeks afterwards. It was observed that the attenuated bacteria gave a protection of 33.3%, in addition to the weak humoral response elicited. Animals inoculated with secreted antigen associated with Freunds incomplete adjuvant and oligodeoxynucleotide containing unmethylated CpG dinucleotides (CpG ODN) showed a strong humoral response, but this inoculation could not prevent the spread of challenge bacteria in the majority of animals. These results demonstrate the immunogenic potential of the attenuated T1 strain in the development of a vaccine against caseous lymphadenitis in goats.

Análise por SDS-PAGE e Western blot de antígenos somáticos e extracelulares de Corynebacterium pseudotuberculosis

Different techniques to isolate secreted, cell-surface located and somatic fractions of Corynebacterium pseudotuberculosis have been studied by SDS-PAGE and immunoblotting, by using a pool of sera from naturally infected goats. The secreted antigens were obtained from culture supernatant of the bacteria grown in a chemically defined medium or in Brain Heart Infusion medium. The surface fraction was obtained by NaCl 1 M treatment and the somatic ones were obtained by using distinct procedures (detergents and ultrasounds). By Coomassie blue staining, we observed 20 bands in the secreted fraction, 35 bands in the surface extract and 40 to 50 bands in the somatic fraction, depending on the extraction procedure. Sixteen immunoreactive proteins were detected among the studied fractions. Bands with molecular weights of 125, 108, 75, 68, 41, 40, 31 and 24 kDa were recognized with higher intensity and all of them were found in the secreted fraction. The use of the chemically defined medium allowed us to evidence the presence of proteins with high molecular masses in the secreted fraction of C. pseudotuberculosis, which had not been previously described.