Passive protection of neonatal calves against bovine coronavirus-induced diarrhea by administration of egg yolk or colostrum antibody powder.

The protective effect of egg yolk and colostrum powders prepared from hens and cows vaccinated with inactivated bovine coronavirus (BCV) antigen was evaluated in a challenge model with a virulent BCV strain. Twenty three calves from BCV-free herds were randomly divided into control and several treatment groups. All calves were orally challenged with 1 x 10(9) TCID50 of the virulent Kakegawa strain of BCV at 24 to 36 h after birth. Calves in treatment groups received either egg yolk powder or cow colostrum containing BCV specific antibodies. Daily treatment with these antibody preparations started 6 h until 7 days post-challenge. Control calves which received no antibody had severe diarrhea and all died within 6 days after infection. In contrast, calves fed milk containing egg yolk or colostrum with neutralization titers of 1:2560 or 1:10,240 respectively all survived and had positive weight gain unlike the other treatment groups. These results indicate that the orally administered egg yolk and colostrum powders protected against BCV-induced diarrhea in neonatal calves and that the egg yolk used provided a higher degree of protection compared to colostrum powder on a titer basis. Treatment with whole egg yolk from immunized hens therefore provides a more efficacious alternative to the existing methods of specific passive protection against BCV.

Passage of chicken egg yolk antibody treated with hydroxypropyl methylcellulose phthalate in the gastrointestinal tract of calves.

Two types of chicken egg yolk antibody samples for oral passage trials in calves were prepared: (1) hydroxypropyl methylcellulose phthalate (HPMCP) antibody powder (HAP)--a powder produced by spray-drying a supernatant obtained after precipitation of lipids from egg yolk with HPMCP and (2) control antibody power (CAP)--a powder produced from an antibody solution with HPMCP. Antibody activity and pattern of distribution of both antibody preparations in the gastrointestinal tract of calves were compared by enzyme-linked immunosorbent assay. At 2 hr post administration, anti-K99 fimbrial antibodies from both the CAP and the HAP were detected in the abomasum of calves with titers of 1:128 and 1:256, respectively. However, at 4 hr, anti-K99 fimbrial titers of the CAP and the HAP were reduced to 1:2 and 1:64, respectively, due to digestion in the abomasum. These results indicated that the egg yolk antibody powder with HPMCP was more resistant against gastric juice in the stomach, thereby, ensuring a transfer of functional antibodies to the small intestine of calves after oral administration.

Research note: avidity of chicken yolk antibodies to enterotoxigenic Escherichia coli fimbriae.

The yolk antibodies from chickens and the serum and colostrum antibodies from cows were obtained after immunization of these animals with inactivated bacterin or purified K99 fimbriae from enterotoxigenic Escherichia coli (ETEC). The avidity of anti-K99 fimbriae antibodies produced from either chickens or cows was measured by competitive binding assay of ELISA. The yolk antibodies competed strongly with the serum and colostrum antibodies from immunized cows and inhibited 40 to 80% of the binding of these antibodies. Results demonstrate that the avidity of antibodies obtained from immunized chickens compares with that obtained from immunized cows. Thus, the yolk antibody from immunized chickens, aside from its use for prophylaxis against some infectious diseases, may also serve as effective ligand for purification of biologically active substances such as fimbrial antigens by affinity chromatographic procedures.