Maternal antibody titers in white leghorn chicks against infectious bursal disease virus (IBDV) were measured by a computer-assisted, single-serum-dilution, indirect kinetic-based enzyme-linked immunosorbent assay (KELISA) and by a virus-neutralization (VN) test in order to predict the timing of initial vaccination. Day-old white leghorns were from unvaccinated pullets or from pullets vaccinated either four times or twice with IBDV commercial vaccines. The chicks were immunized once via the drinking water with a commercial "intermediate" live IBDV vaccine at 1, 15, or 28 days of age. Effective initial immunization was confirmed by an increase in antibody to IBDV (serologic conversion) that occurred when maternal antibody decreased to 8 and 9 on a log2 scale. This concentration of antibody was detected between 24 and 28 days of age. The computer-assisted IBDV-KELISA increased the sample processing speed for detecting IBDV antibody, and it was as sensitive as the VN test for predicting the timing of initial IBDV vaccination.
A computer-assisted single-serum-dilution indirect kinetic-based enzyme-linked immunosorbent assay (KELISA) was used for quantitating the natural decay rate of infectious bursal disease virus (IBDV) maternal antibody in progeny obtained from white leghorn breeders. The KELISA results were compared with those of a standard virus-neutralization (VN) test. Pullets were subjected to two IBDV immunization regimens. Group 1 was vaccinated at weeks 0, 2, and 10 with two live vaccines in drinking water and at week 20 with an oil-emulsified (SC) IBDV vaccine, group 2 received only the first and last immunizations, and group 3 served as the unvaccinated control. Pullets were artificially inseminated at 28 weeks of age. Progeny chicks from each group were bled every other day for 47 days. Both KELISA and VN test detected linear relationship in the decay of maternal antibodies. The VN test detected no significant differences (P greater than 0.05) in the IBDV maternal antibody titers at day 1 or in the rate of decay between the progeny from groups 1 and 2. The VN maternal antibody titers decreased at a rate of 0.16 log2 titer per day. In contrast, KELISA revealed higher IBDV maternal antibody titers in day-old progeny from pullets vaccinated 4 times (log2 = 14.3). However, KELISA titers of progeny from this group decreased at a faster rate than titers of progeny from pullets vaccinated twice (0.20 vs. 0.13 log2 titer per day).
The serologic relatedness of six avian reovirus isolates (CO8, S1133, 81-5, 2408, 1733, and UMI 203) were determined using a virus-neutralization (VN) test and an enzyme-linked immunosorbent assay (ELISA). Six groups of 20 specific-pathogen-free broilers each were twice infected with one of the six isolates per group. Serum was reacted against each isolate in a beta VN test in chicken embryo kidney cells and against the S1133 virus in ELISA. Relatedness (R) values, determined by cross VN, revealed that all belonged to a single serotype. However, the CO8 isolate represented a major subtype difference compared with the other isolates. R values among the five other isolates indicated minor or no subtype differences. ELISA also showed major differences between the CO8 and the other isolates.
The kinetics of the enzyme-substrate reaction served to evaluate a single-serum-dilution indirect enzyme-linked immunosorbent assay (ELISA) for quantitating antibody in white leghorn hens inoculated with infectious bursal disease virus (IBDV) vaccines. The antibody profiles of primary and secondary responses induced by two IBDV immunization regimens were compared using a kinetic-based ELISA (KELISA) and the virus-neutralization (VN) test. KELISA was standardized with an IBDV-infected VERO cell suspension. Antigen was capable of binding minute quantities of sample (5 microliter) without requiring dilutions. Conjugate consisted of immunoglobulin G fraction of goat antiserum against chicken IgG bound to horseradish peroxidase. Neither test revealed a difference in antibody profiles between the two immunized groups. The KELISA was as efficient as the VN test in detecting antibody after vaccination and one log 2 unit more sensitive. The KELISA was suitable for testing large numbers of samples (n = 60) in a microplate compared with a conventional ELISA (n = 8).
An indirect enzyme-linked immunosorbent assay (ELISA) was developed to measure humoral antibody responses of chickens against Pasteurella multocida. A standard indirect hemagglutination (IHA) test was used to compare serologic results with those of ELISA. The ELISA was also used following challenge with P. multocida to compare the efficacy of three commercial fowl cholera vaccination regimens. Although antibody titers measured by ELISA and IHA were highly correlated, ELISA was at least twice as sensitive as IHA. Antibody measured by ELISA and IHA also correlated significantly with protection against P. multocida challenge. No mortality occurred in any of the three vaccinated challenged groups. However, control unvaccinated chickens experimentally infected with P. multocida developed signs of acute pasteurellosis and died by the 10th day post-challenge. Impression smears made of hepatic tissue from all chickens were stained (Wright's stain), and typical bipolar rods characteristic of Pasteurella were identified in smears from unvaccinated challenged controls only.
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