Identification and characterization of infectious bursal disease virus subviral particles by capillary zone electrophoresis: potential application for vaccine production and quality control.

The infectious bursal disease (IBD) causes immunosuppression in chicken of all ages and high mortality in young chicken, posing serious threat to poultry industry worldwide. One promising strategy for preventing this highly contagious disease is using recombinant subunit vaccine, employing VP2 subviral particles (SVP) as epitomic antigen. Analytical techniques of viral-like particles such as SDS-PAGE, western blot, or high-performance size-exclusion chromatography have been widely applied, but mostly unsatisfactory. In the present study, a simple, fast and cost-effective capillary zone electrophoresis (CZE) method with UV-detection was developed to analyze purified IBDV-SVP (expressed by Escherichia coli system) using commercial monoclonal antibody (mAb) against VP2. To find satisfying CZE conditions, injection mode, separation voltage, and separation buffer were explored. Through the modified CZE, mAb and SVP could be well separated and shown distinct peaks in the electropherogram. Furthermore, to determine the stoichiometry, the area of the mAb peak versus SVP/mAb binding ratio was plotted and indicated that 2 or 3 receptor molecules were bound per SVP. The purity and integrity of SVP and the interactions between SVP and mAb could be analyzed by the developed simple CZE-UV method in less than half hour. This CZE-UV method proved to be a valuable and useful tool in detection, characterization, and quantification of IBDV-SVP and the mAb, offering potential applications of in-process quality control of vaccine production, surveillance of serum antibody produced against IBDV infection, or vaccine immunization.

Pharmacokinetics and tissue depletion of doxycycline administered at high dosage to broiler chickens via the drinking water.

The recommended use of doxycycline (DC) to broiler chicken is 100 mg/L via the drinking water and a 7-day withdrawal time (WDT). However, study of a higher dosage is desirable because of the possible increase of antimicrobial resistance and disease spectrum. Tissue DC residues exceeding the current maximum residue levels (MRL) was our major concern. Therefore, serum concentration and tissue depletion of DC hyclate after administration of 200 mg/L of DC in the drinking water for five consecutive days were studied. The steady-state DC concentration (8.3 ± 0.9 µg/mL) was reached on the third day of medication. The elimination constant (0.05 ± 0.01 1/h), half-life (14.9 ± 1.4 h), area under concentration versus time curve (81.0 ± 9.9 h·µg/mL) and mean residence time (22.7 ± 2.5 h) were obtained using a non-compartmental pharmacokinetic model. It was determined that the current 7-day WDT regulation was still legitimate for the kidney and liver as well as for the breast and leg muscles, which were estimated by linear regression analysis of the 99% upper distribution limit. The unregulated heart and gizzard were considered safe even when the lowest MRL of muscle (100 ng/g) was applied. While at the present time the extra-label use of drugs is only allowed under specific conditions, in the future it may become necessary to increase the general dosage of DC, and the current results suggest a safe range of DC hyclate in chicken; however, skin/fat tissue residues warrant further studies.