Evaluation of DF-1 cell culture based vaccine development for infectious bursal disease virus in Ethiopia

Infectious Bursal Disease is a highly contagious, immunosuppressive viral disease of young chicks caused by the Infectious Bursal Disease Virus (IBDV). The study was carried out at the National Veterinary Institute (NVI) of Ethiopia to evaluate the competence of the DF-1 cell culture adapted vaccine strain of IBDV as a vaccine candidate. DF-1 cells at passage 27 confluent monolayer was infected with 1 ml of LC-75 vaccine strain virus by adsorption method and recorded as passage 1 (P₁). This procedure has been repeated up to seven serial passages with the same methods of virus infection onto DF-1 cells. Minor CPEs were observed in the second passage, but vivid cytopathic effects (CPE) were observed starting from passage 3 (P₃). The infectivity titer of DF-1 cell adapted virus was determined, and the results showed a linear increase in titer with each passage number. Transcriptase polymerase chain reaction (RT-PCR) targeting the VP2 gene revealed positive 400-base pair amplification. The vaccinated experimental chicks from passages 5 and 7 and the CFC based vaccine showed no clinical signs and/or death. Efficacy test revealed that DF-1 adapted vaccinal strain protected the chicks from the challenged virus strain at passage 5 and 7. The control group, on the other hand, had 100 % morbidity and 91 % mortality. As a result, the DF-1 cell could be used as a model to study IBDV kinetic growth, and the DF-1 cell adapted virus could be a candidate for IBD vaccine development. Thus, IBD vaccine production using DF-1 cells is recommended.