Crop Immune Response Post–Salmonella Enteritidis Challenge in Eight Commercial Egg-Layer Strains and Specific-Pathogen-Free White Leghorn Chickens

SUMMARY. The crop immune response against Salmonella Enteritidis (SE) challenge in eight commercial egg-layer strains (five white-egg layer and three brown-egg layer) and specific-pathogen-free (SPF) White Leghorn (WL) hens was investigated. Preand post-SE challenge mucosal immune responses within the crops were evaluated. Commercial layers and SPF WL hens were orally challenged with 10 8 CFU/ml SE PT13a and SE nalR PT13, respectively. Crop lavage samples were collected at weekly intervals from day 0 (pre-challenge) to day 25–27 postinfection (PI), and bacteriological examination was performed to monitor progression of SE infection. Crop lavage samples were analyzed for SE-lipopolysaccharide (LPS)–specific IgA using enzyme-linked immunosorbent assay (ELISA). HE however, at day 25–27 PI SE persisted in crop lavage samples from SPF WL hens and three commercial white-egg layer strains. A marked increase in SE-LPS-specific IgA was measured in crop lavage samples between day 0 and day 11–12 PI for all hen groups. Crop SE-LPSspecific IgA response remained elevated above day 0 baseline for the duration of the experiment. Well-defined score 3 to 5 lymphoid tissue aggregates were observed in crop tissue sections harvested at day 34 PI. Comparison of crop sections determined a 1.2–4.0 times increase in ratio of lymphoid tissue in day 34 PI SE-challenged hens vs. uninfected control hens. RESUMEN. Respuesta inmune en el buche frente a un desafo ´o con Salmonella Enteritidis en ocho lo ´neas de ponedoras