Identifying the immunocompetence markers at weaning to predict long-term vaccine response and persistence in pigs

Vaccination is a key strategy for controlling infectious disease in pigs, but the magnitude and persistence of vaccine-induced immunity vary among individuals. We investigated whether immune and physiological traits measured at weaning could predict long-term antibody (Ab) status and Ab persistence following vaccination against Mycoplasma hyopneumoniae (MH) and Influenza A virus (IAV), and whether predictive markers were shared between vaccines. Two vaccination trials were conducted in a cohort of 381 Large White pigs (MH, n=189; IAV, n=192). Animals were vaccinated at weaning (28 days of age) and received a booster 21 days later. Long-term Ab status was defined at 118 days post-vaccination (dpv) using assay-specific thresholds, while Ab persistence was defined as the decline from the individual peak response at 28 or 35 dpv to 118 dpv. A broad panel of immune and physiological traits measured at weaning was evaluated as candidate predictors. Sparse Partial Least Squares Discriminant Analysis (sPLS-DA) was used for variable selection, followed by PLS-DA classification models. Cross-validated accuracies ranged from 64.7% to 67.7%, indicating moderate predictive performance. Across vaccines, eight predictors were shared for long-term Ab status and twelve for Ab persistence. Hematocrit, IgG, platelet count, and plateletcrit (PCT) were associated with positive long-term Ab status for both vaccines, whereas mean corpuscular hemoglobin concentration (MCHC) and neutrophil percentage were associated with negative status. For persistence, higher vitamin D, -1 globulin concentration, platelet count, and PCT were consistently associated with persistent responses across vaccines, while MCHC and spectral absorbance traits were associated with non-persistence. These findings indicate that early-life immune and physiological traits measured at weaning are associated with immunocompetence traits that contribute to variation in subsequent long-term vaccine antibody outcomes and responsiveness. The identification of both shared and vaccine- or phenotype-specific predictors suggests that vaccine responsiveness reflects both general features of baseline immunocompetence and context-specific determinants.