Growth and replication of infectious bursal disease virus in the fish cell line as an experimental vaccine

Recently, several attempts have been made to replace egg-based with cell-based vaccines to prevent and control Infectious Bursal Disease Virus (IBDV). This study aimed to evaluate a new fish cell line (M99) for culturing and replicating IBDV. After observing complete cytopathic effects (CPE) on the M99 cell line, virus titers were determined using the TCID50 test, and the presence of the virus was confirmed using an RT-PCR test. Subsequently, 135 broiler chickens (14 days old) were randomly divided into three equal groups for immune response measurements: G1: immunized with a commercial vaccine, G2: immunized with an experimental vaccine, and G3: control. Antibody responses, bursal index, and histopathological evaluations were examined on different days after immunization. Based on the results, CPE of the virus was noticeable from the first passage, becoming complete by the third passage. The infectious titer of the virus was log10^6.9. Antibody titer measured 21 days after immunization in both vaccinated groups were significantly differed from the control group (p < 0.05). The results obtained from examining the bursal index and histopathological evaluations showed no significant difference between the studied groups at different times. Overall, this research is the first report on the successful cultivation of infectious bursal virus on a permanent cell line of fish origin, with the advantages of tolerance to a wide temperature range (26-40 degrees Celsius). Therefore, this cell line has potential for use to attenuate, cultivate, and adapt other pathogens to cold temperatures in future studies.