Immunization of the laying hen: Production and application of egg yolk antibodies

The laying hen deposits antibody into egg yolk to confer passive immunity to the newly hatched chick. Apart from its natural function, the egg yolk can be considered a discrete package of antibodies useful for a variety of diagnostic, therapeutic, and prophylactic applications. New antibody applications that require large quantities of antibodies are limited only by egg cost. The overall objective was to find strategies to increase egg yolk antibody yield.;Initial experiments were conducted to demonstrate utility of hens for polyclonal antibody production. An improved immunization protocol for the production of antibody specific to botulinum-neurotoxin was developed. Egg yolk antibodies were demonstrated to be useful for the detection and neutralization of botulinum-neurotoxin. Hen age and induced molt had minimal effects on egg yolk antibody to soluble protein antigen (SPA); hence, polyclonal egg antibody production may be an alternative commercial use for spent hens. Egg size and laying frequency had no apparent effect on egg antibody levels; therefore, egg cost could be limited by utilizing hens that produce the largest eggs at the highest laying frequency. It was concluded that utilization of egg antibody platform could be a potentially rapid and scalable method to produce Kg quantities of egg antibody.;Recent discoveries of the mechanisms by which microbial products act as adjuvants led us to hypothesize that additions of killed, whole-cell bacteria (bacterins) to Freund Complete Adjuvant (FCA) at the primary immunization could improve hen antibody responses to SPA. Addition of Gram-negative bacterins (e.g. E. coli) or Gram-positive bacterins (e.g. S. aureus) to FCA either decreased (50%) or increased (1.7-fold) antibody production to SPA, respectively.;Acute exogenous corticosterone has been shown to increase antibody response in mammals; hence, experiments were conducted to determine the effect of exogenous, dietary corticosterone on hen antibody response to SPA. Corticosterone administered during primary immunization increased egg yolk antibody 3-fold; however, the application of this strategy for commercial production of egg antibody could be limited due to decreased egg production of corticosterone-fed hens. Developing successful strategies for increasing egg antibody yields has remained a challenge for the continued growth in commercial egg antibody applications.