Oral immunoadjuvant activity ofLactobacillus caseisubsp.caseiin dextran-fed layer chickens

Abstract

We recently reported that synbioticLactobacillus caseisubsp.caseitogether with specific substrate dextran elicited an enhancement in humoral immune response against bovine serum albumin (BSA) as a model antigen in BALB/c mice. The present study was designed to evaluate the oral immunoadjuvant effects of the synbiotic in layer chickens. Using a PCR assay,L. caseisubsp.caseiwas detected specifically in the intestinal chyme of chickens (10d of age, Julia strain) fedad libitumon a diet supplemented with 75mg dextran/kg (dextran-supplemented diet, DSD) and administered orally with 107colony-forming units (CFU)L. caseisubsp.caseiin 0·1ml PBS with the aid of an intubation needle at 1, 2 and 3d of age. Furthermore, oral administration of 107CFUL. caseisubsp.caseiat 1–3d of age significantly enhanced the production of anti-BSA antibody in DSD-fed chickens (60d of age) administered orally with 1mg BSA at 32 and 33d of age and subcutaneously with 5μg BSA at 33d of age. In addition, among bacterial numbers tested, 106CFUL. caseisubsp.caseitogether with dextran induced an effective increase in humoral immune response to mixed inactivated vaccines against Newcastle disease and avian infectious bronchitis, and the treatment may be advantageous in protecting against these infectious diseases in chickens in actual application. These results suggest that dietary supplementation ofL. caseisubsp.caseiwith dextran leads to immunomodulation of humoral immune responses.