Construction of an Evaluation Model for the Protective Efficacy of Ovine Brucellosis Vaccines

This study developed a comprehensive model for evaluating sheep brucellosis vaccine efficacy by integrating bacteriological, immunological, and pathological indicators.Thirty-three healthy Xinjiang fine-wool sheep were challenged via conjunctival instillation with Brucella melitensis strain M28, and paired lymph nodes, spleen, and serum were collected post-infection. Principal Component Analysis (PCA) identified three principal components (81.935% variance), whose comprehensive score (F) strongly correlated with average bacterial load ( P  < 0.01, AUC = 0.905); key indicators included left submandibular, left prescapular, and left inguinal lymph node bacterial loads, and cELISA antibody titers. An optimized stepwise regression model retained 9 indicators (SAT, cELISA, cELISA (BS), IL-12, IL-17, left parotid lymph node bacterial loads, left submandibular lymph node bacterial loads, left parotid lymph node gross anatomical scores, right parotid lymph node gross anatomical scores). This model (R) demonstrated superior predictive accuracy (AUC = 0.974, Rho = 0.864 vs. PCA's 0.905 and 0.768) and revealed IL-17 positively and IL-12 negatively regulated bacterial load. This study presents the first comprehensive system for sheep brucellosis vaccine efficacy, offering robust technical support for eradication efforts.