Df-1 Cell Adaptation and Immune Responses of Lc-75 Vaccinal Strain ofInfectious Bursal Disease Virusin Chicken

Abstract

The currentInfectious bursal disease virus(IBDV) vaccine strain of LC-75 in Ethiopia is being produced through chicken embryo fibro blast cell which has short lifespan and limited need of specific pathogen free eggs. Ideally, vaccine should have better longevity and being effective in cost and time. Experimental research was conducted to adopt DF-1 cell and to validate the immune responses, immunosuppressive effect and immunogenicity tests, of LC-75 vaccinal strain ofInfections bursal diseases virusA total of 76 chickens were used for these experiments. The seroconversion rate of the vaccine were measured using haemaglutination inhibition (HI) test in the vaccinated two experiment groups, adapted IBDV and Newcastle vaccines at two weeks interval for the first group and only Newcastle vaccine for the second experiment groups. To perform the immunogenicity test, two groups having 20 chickens per group were used and samples of serum were taken on 0-, 7-, 14- and 28-days post vaccinations and subjected to indirect ELISA test. The group that received both vaccine types produced haemagglutination inhibition titer (HIT) of 97.33±22.49 whereas the other group that received only Newcastle vaccine produced 124±24.92. The control group always showed no detectable antibody while the vaccinated group was able to produce average antibody S/P values of 0.00 ± 0.01 at day 0, 0.02± 0.01 at day 7, 1.05±0.10 at day 14 and 0.83±0.05 at day 28. RT-PCR using a 400 bp IBDV viral protein 2(VP2) specific primer resulted from positive bands in all samples. In conclusion, the vaccinal strain was able to replicate and adapt on the DF-1 cells and it was found to be immunogenic as well as less immunosuppressive.