Fig. 2
Brucella LPS epitopes and antibody response in RB51 vaccinated cattle. A Schematic representation of S- and R-LPSs and SDS-PAGE of silver-stained protein-free S-LPS [70] from B. abortus 2308 revealing by densitometry the proportion range of R- and S-LPSs (adapted from [69]). B Western-blot performed with protein-free S-LPS and sera from cattle of brucellosis-free herds. (1) Unvaccinated heifer (negative control); (2) positive reaction with the serum of a RB51 vaccinated heifer that aborted after vaccination and from which RB51 was isolated (this serum was taken 12 months after vaccination); (3) strong positive control with the serum of a rabbit hyperimmunized with acetone-killed RB51 cells. C Serological responses of RB51 vaccinated cattle in iELISA (INGEZIM Brucella Bovina 2.0 -Gold Standard Diagnostics-, left) and cELISA (Svanovir Brucella-Ab C-ELISA -Svanova-, right) commercial tests for the diagnosis of bovine brucellosis performed following the manufacturing instructions. The cut-off (line in blue) resulting in maximal diagnostic sensitivity and 100% Diagnostic Specificity was established in both tests with a representative collection of gold standard sera taken from B. abortus culture positive and brucellosis free cows. Sera from RB51 vaccinated RBT-negative cows (green squares) were obtained from 5 to 8-month-old brucellosis-free heifers vaccinated with the full dose (1–3.4 × 1010 CFU) of RB51 (CZ Vaccines. Porriño. Spain), bled between 9 and 18 months after vaccination and maintained in a brucellosis-free environment