Systemic and Mucosal Intestinal Antibody-Response of Sheep Immunized with Aromatic-Dependent Live or Killed Salmonella-Typhimurium

Following the development of a suitable formulation capable of inhibiting intestinal proteolytic activity, the total anti-lipopolysaccharide (LPS) and anti-flagellin (Fla) antibody response and isotype in the sera and intestinal washings of sheep, immunized with live aromatic-dependent (aro-) Salmonella typhimurium strain CS332 by the intramuscular (live i.m.) or oral (live oral) route or acetone-killed virulent S. typhimurium by the intramuscular route (killed i.m.), were determined at various intervals post-immunization. The serum or intestinal anti-lipopolysaccharide (LPS) or anti-flagellin (Fla) antibody titres of immunized sheep, regardless of the route of immunization, were significantly greater (P < 0.01) than those of non-immune control sheep. Although significant differences between the serum anti-LPS or anti-Fla antibody titres of sheep in various immunization regimes were observed, they were not consistent for different periods post-immunization. The predominant isotype contributing to serum anti-LPS antibody activity was IgM whereas the serum antiflagellar antibody activity was confined to IgM, IgG1 and IgG2. In either case, the contribution of the IgA antibody isotype was minimal