The Analysis Of The Effect Of Three Factors On Chicken Immunization

Vaccination is a very important measure for the prevention and control of avian diseases. In this study, we analyse three factors influencing effect of vaccination in order to supply the theoretical basis for the enhance of poutry vaccination effect.1. The vaccine was contaminated. There are the phenomena that FPV vaccine was contaminated by REV. In order to isolate reticuloendotheliosis virus (REV) from suspected live vaccines with other viral contamination, 7-day-old SPF chickens were inoculated with fowl pox live vaccines from different manufactures. Five days later, plasma samples were collected and inoculated into chicken embryo fibroblast (CEF) monolayer. CEF cultures were trypsinized a week later and cell suspensions were re-plated into fresh dishes and incubated for another week. After two passages, CEF monolayers were stained in indirect fluorescence antibody test with REV-specific monoclonal antibody and REV infection was demonstrated in one CEF culture. The REV isolate was designated as JS0809. Genomic DNA was extracted from the infected CEF and used as template for amplification of its env gene. Sequence analysis indicated that its env ORF contained 1761 bp same as the most published strains and had very high sequence identity of 96%-99.8% with all compared strains. Relatively, it had lower homology of 96%-97.3 with early isolated reference strains but higher identity of 99.5%-99.8% with the recent isolates. It had 97.% of identity with REV integrated into a fowl pox vaccine virus reported in Australia but 99.8% of identity with REV integrated into a fowl pox virus (FPV) field strain reported in US. The study demonstrated the REV contamination in fowl pox live vaccine made in China and env sequence of the contaminated REV was very close to FPV field strains isolated recently. This is the first report to isolate REV from fowl pox live vaccine in China.2. Disease which can suppress immune function. ALV-J (Subgroup J of Avian Leukosis Virus) may lead to B cell maturation arrest, and inhibition of T lymphocyte development block, then leading to immune suppression.In this experiment, four groups of 1 day old Highland brown egg chickens with and without maternal antibodies are infected with ALV-J by intraperitoneal inoculation and contacts with the cage, three biological indicators which refers to viremia, cloacal detoxification and antibodies were monitored. The results showed that: the group with maternal antibodies & inoculated virus, produced a lower level of viremia at 4 weeks of age, 84% of the chickens occur a transient phenomenon of detoxification, there is a chicken resistant to ALV-J infection ( 8%); the group without maternal antibody group & inoculated virus, exist higher levels of viremia in 2 weeks, and has remained, 88% of the chickens showed the phenomenon of continuous detoxification; two contact group, with or without maternal antibodies, each has a chicken showed a V-P27+A-state. This study indicates that early infection of ALV-J maybe causes the chicken's immune tolerance, and has the spread ability. Maternal antibodies has an important effect for delaying the early infection and the level of detoxification. In the study, through early ALV-J infection in chickens, we found that maternal antibodies can slow down the occurce of viremia in the chicken inoculated ALV-J early, so we hope it can provide a theoretical basis for enhancing immune effect, and ultimately achieving a good immune effects.3. Maternal antibody interference. In recent years, the phenomenon that broiler immune IBDV (Infectious bursal disease) vaccine failures have reported usually. Without determining the best immune time according to the level of maternal antibody the first free day is a mian reason that caused immunological failure. The study tested IBD maternal antibody level in different age periods, the data show that IBD maternal antibodies has a half-life of 3.2 to 4.15 days; At the same time, three kinds of medium virulence of IBD vaccine were inoculated at the 7,10,13,16,20,23 day old, then the relationship between antibody level and different immunization days were compared under different levels of maternal antibodies. The results showed that at 2 day old in the maternal antibody levels 2⁹¹⁴ (ELISA measured value) , most of the chickens at 7,10 old day do not produce antibody response. when the average maternal antibody ELISA titer at 2 days old was 2^12.56, IBDV-MB produced by Israeli ABIC produce antibody response rate which was 0/24, 13/25, 22/23 at 13,16,20 old day immunity; when the 2 day average maternal antibody ELISA titer was 2^10.77, the group which use Schering-Plough vaccines are respectively 12/14, 14/15, 13/14; when 2 days old maternal antibody ELISA average titer was 2^11.52, the group which use Merial vaccine immunization are respectively, 9/13, 14/15, 14/14 antibody response at 16,20,23 days. The experiment studies the effect of maternal antibodies on antibody respose , the results supply theoretical basis for the IBD vaccine effect.