Suppression of Salmonella enterica serovar Enteritidis excretion by intraocular vaccination with fimbriae proteins incorporated in liposomes

Abstract

Liposome-associated fimbriae antigens (SEF14 and SEF21) were prepared for intraocular immunization to seek protective efficacy for intestinal infection with Salmonella enterica serovar Enteritidis. Chickens were immunized intraocularly with the antigens at 8 and 10 weeks of age. Evidence of an IgA and IgG responses were found in the intestinal tract and in sera of these chickens. Antibody-secreting lymphocytes were detected in the Harderian gland of immunized chickens as determined by enzyme-linked immunospot assay. Two weeks after the booster immunization, the chickens were challenged orally with 1x10(7) live Salmonella Enteritidis, and fecal samples were examined for bacterial excretion from the intestinal tract. Significantly less fecal excretion of bacteria was observed in immunized chickens for 15 days after challenge. The numbers of bacteria in the intestinal contents (caecum and rectum) were also significantly lower in immunized chickens than in unimmunized controls. Detection of S. Enteritidis-specific DNA by the polymerase chain reaction was consistent with the bacterial observations. Intraocular immunization with liposome-associated SEF14 and SEF21 therefore elicits both systemic and mucosal antibody responses, so that bacterial colonization in the intestinal tract and excretion of S. Enteritidis in the feces are suppressed by immunization.