Isolation and propagation of infectious bursal disease virus using the ovine kidney continuous cell line

Twenty-six samples known to contain infectious bursal disease virus (IBDV) were examined by virus-isolation attempts on ovine kidney (OK) cell line, Vero cell line, and chicken embryo fibroblast (CEF) cultures. Virus was isolated from two of 26 samples, three of 26 samples, and three of 25 samples on OK, Vero, and CEF cultures, respectively. However, in contrast to IBDV replication in Vero and CEF cultures, isolated virus was unable to induce serially sustained cytopathic effects (CPE) during successive passages in the OK cell line, unless cell lysates were treated with chloroform between every other passage. The cytopathogenicity of the untreated virus passaged in OK cells was revived and maintained upon passage in Vero cells. An initial single passage of laboratory or field material in OK cells followed by further passages in Vero cells resulted in virus isolation from six of 26 samples, which was better virus recovery than when either cell line was used alone or when CEF cultures were used. Twenty of the 26 test samples were originally positive when examined by nucleic acid hybridization with radiolabeled IBDV cDNA, indicating that some of the samples that were negative upon virus isolation using OK and Vero cells may have contained inactivated virus.