RhinoVax® is an Efficient Adjuvant in Oral Immunisation of Young Chickens and Cholera Toxin B is an Effective Oral Primer in Subcutaneous Immunisation with Freund's Incomplete Adjuvant

Abstract

Forty-five approximately 50% in-bred 14-day-old White Leghorn female chickens (Gallus domesticus) originating from 11 hens were distributed into 5 treatment groups containing one sister in each treatment group. Phase 1 involved oral administration of an antigen, Bovine Serum Albumin (BSA), in combination with various adjuvant preparations, either Cholera Toxin B-subunit (CTB) and/or RhinoVax^® (RV). A positive control group received BSA emulsified in Freund's Incomplete Adjuvant (FIA) by subcutaneous injection. All chickens responded with immunospecific IgA, IgM and IgG antibodies in their circulation. Classical parenteral immunisation with FIA was generally the most potent mode of antigen administration. The highest immunospecific IgG concentrations recorded in the orally-immunised chickens were in the group immunised with 20% RV as the adjuvant. The concentration in this group was approximately 5 times lower than that recorded in the FIA group. For practical egg yolk polyclonal antibody production purposes, the oral regime using 20% RV as adjuvant seems an attractive alternative to the more invasive technique of injecting the antigen in FIA emulsions. In Phase 2 all chickens were subjected to traditional subcutaneous immunisation with a new antigen, human IgG emulsified in FIA. The two groups of chickens that had received CTB orally during Phase 1 responded with significantly higher immunospecific antibody concentrations than did the other chickens, indicating that oral administration of CTB prior to traditional parenteral immunisation may have a priming effect on the humoral immune system. The immunospecific antibody response varied between the 11 families of chickens. There was no correlation between familial responsiveness to oral and subcutaneous immunisations. Families that were high responders to oral immunisation were not high responders to parenteral immunisation and vice versa.