Effect of nanochitosan on immunogenicity of Aeromonas hydrophila oral vaccine in Cyprinus carpio

    Although oral vaccination has numerous advantages over other routes, degradation of the vaccine antigens in the gut and low uptake in the gut associated lymphoid tissue of the gastrointestinal tract still complicate the development of oral vaccines in fish. Chitosan nano- particles have recently been shown to possess significant potential as oral drug delivery systems. In this study chitosan  nanoparticles were prepared and characterized with respect to size and morphology then used as oral adjuvant with Aeromonas hydrophila vaccine (AHB) in Cyprinus carpio. Three hundred and sixty juvenile C. carpio (46.5±4.67 g) were randomly divided in four groups in triplicates. Groups 1 and 2 received orally AHB and AHB + nanochitosan respectively. Fish in groups 3 received nanochitosan in food, whereas group four received just basal diet free AHB or nanochitosan. Experimental diet of each group administrates at days 1-5 and 20-25 of study. Blood samples were taken from all groups at days 25, 40 and 55 of study. Immunological parameters including: serum lysozyme, bactericidal and complement activity, leukocyte NBT activity as well as serum IgM and anti A. hydrophila antibody titer were compared among the groups. Then, fishes of each groups challenged with live Aeromonas hydrophila and mortality rate recorded for 10 days. Results showed that some none specific immunological parameters improved significantly. Serum lysozyme, bactericidal and NBT activity increased in group 2 (vaccine + nanochitosan) in all sampling periods (P<0.05). Slight increase in immunological parameters were seen in groups 1 and 3. Complement activity showed no significant change among the groups. although anti A hydrophila antibody titer were increased significantly in groups 1 and 2 at 25 and 40 days of study (P<0.05), no change were seen among the groups in anti A. hydrophila antibody titer at 55 days of study (P>0.05). Mortality after challenge with A hydrophila didn’t affected by oral vaccination with AHB or AHB+nanochitosan. There were no significant change in mortality rate among the groups (P>0.05). Conclusively, although immunization with  AHB and nanochitosan in oral route improve some none specific immune response of C. carpio, no significant change in anti A hydrophila antibody titer and challenge mortality rate were seen in treated fish.