Uptake and processing of biofilm and free-cell vaccines of Aeromonas hydrophila in Indian major carps and common carp following oral vaccination — antigen localization by a monoclonal antibody

Abstract

Uptake and processing of biofilm (BF) and free-cell (FC) vaccines of Aeromonas hydrophila were studied in the Indian major carps catla Catla catla, and rohu Labeo rohita and in the common carp Cyprinus carpio following a single dose oral vaccination of 1011 CFU g–1 fish. Fish were sampled at 0.5, 1, 3, 6, 12, 24 h and at 2, 3, 5 and 10 d following vaccination and antigen localization was studied in the gut, kidney and spleen employing monoclonal antibody based immunofluorescence and immunoperoxidase. The general pattern of antigen localization was similar in catla, rohu and common carp. Initially, both the BF and FC antigens were localized in the gut lumen, followed by their uptake by intraepithelial vacuoles and macrophages. Antigen administered orally was also seen in the spleen and kidney. Both BF and FC antigens were detected in the gut lumen of carp within 30 min following oral delivery. However, BF antigen remained in the lumen of the hindgut for 48 h compared to 6 h in the case of FC antigen. In the early stages, BF antigen was localized in the gut epithelial vacuoles while FC antigen was associated with the small macrophages of the hindgut. Antigen localization in spleen and kidney was observed at 3 h and persisted even up to 10 d following oral delivery. In general, there was a distinct difference between BF and FC vaccines in the duration of retention and quantity of uptake in the gut, kidney and spleen.