| Summary: | In the present study, Vero cell line was tested for its ability to support the replication of indigenous very virulent infectious bursal disease virus (vvIBDV). The frozen cells were resuscitated to prepare monolayer, which was further sub-cultured to prepare semi-confluent monolayers using M199 growth medium supplemented with 5% foetal calf serum. The semi confluent monolayers were then infected with 0.25 ml of indigenous vvIBDV. The passage 1 virus was harvested and used for the next passage. In this way virus was given three serial passages on Vero cell line, where characteristic cytopathic effects (CPEs) were observed. During the first passage, no CPEs were found. The Vero cell monolayers remained normal in first passage upto 144 hours post-infection. During second passage, rounding of cells was observed after 72 hours of infection. However, clear and consistent CPEs were not observed in 2nd passage. Typical aggregation, rounding and granulation of Vero cells was noticed in passage 3 (P3) from 72 hours upto 144 hours post-infection. The positive results of agar gel precipitation test (AGPT) confirmed that the adapted (P3) virus was IBDV. The infectivity titer of adapted vvIBDV was found to be log10 7.60 TCID50/ ml at 72 hours post-infection. The indigenous vvIBDV was well adapted to Vero cell line after three successive passages.
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