Isotype-Specific Antibody Responses of Cattle to Salmonella Dublin Lipopolysaccharide and Porin Following Salmonella Dublin Vaccination and Acute and Chronic Infection
2001
Stimulation of different T-cell subsets during antigen presentation influences the antibody isotype response to an antigen. Salmonella infection and Salmonella bacterin vaccination are likely to stimulate different T-cell subtypes. The objective of this study was to determine whether there are differences in the isotype response of cattle to Salmonella antigens following Salmonella infection and Salmonella bacterin vaccination. Sera from Salmonella bacterin–vaccinated, experimentally infected, and chronically infected (carrier) adult cattle collected during previous studies was used to evaluate the IgG₁, IgG₂, and IgM isotype responses of cows to Salmonella serotype Dublin lipopolysaccharide (LPS) and porin. Following vaccination and experimental oral infection, IgG₁ titers to LPS and porin rose more quickly and persisted longer than did IgG₂ titers. In contrast to Salmonella infection, bacterin vaccination stimulated a weak response to Salmonella porin. Salmonella infection also induced a higher IgG₂:IgG₁ titer ratio to LPS than did bacterin vaccination. Chronic Salmonella infection induced the highest LPS and porin IgG₂:IgG₁ titer ratios and the highest correlation between LPS and porin titers. Response operating characteristic curves for each isotype-specific enzyme-linked immunosorbent assay (ELISA) were determined to evaluate the effect of isotype on the sensitivity and specificity of Salmonella ELISA serology for distinguishing sera of Salmonella carriers from those of vaccinated and acutely infected cows. IgG₂ titers to LPS and porin provide a more specific indicator of chronic Salmonella infection status than do IgG₁ titers to the same antigens with little to no loss in sensitivity.
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