Growth and Cytopathogenicity of a Field Isolate of Fowl Poxvirus in Chicken Embryo Fibroblast Cell Culture

The use of developing chicken embryo still remains to be a most important tool for initial virus isolation, and primary chicken embryo fibroblast (CEF) cells have been extensively used to propagate and study the virus in the laboratory. Therefore, the present study was designed to study cytopathogenic characters of a local field isolate of fowl pox virus (FPV) grown in CEF cell culture. The field isolate was inoculated in CEF cell culture, and cytopathic effects (CPEs) were examined in both unstained and May-Grunwald–Giemsa stained cells. The CPE included cellular rounding and clumping from the very first passage and cellular vacuolation and intra-cytoplasmic inclusions were detected from third passage onwards. On fluorescent antibody staining, the yellow-green fluorescence was seen in the perinuclear areas, whereas inclusion bodies were evident in cytoplasm in the form of intense areas of fluorescence. The viral antigen in infected CEF supernatant was confirmed by AGPT and CIE. The infectivity titres of virus in CEF cells increased gradually from 10^2.28 50% tissue culture infective dose (TCID₅₀)/0.1 ml at second passage to 10^5.11 TCID₅₀/0.1 ml at fifth passage indicating gradual adaptation of the virus in the CEF cells.