Studies on vaccine strain of Fowlpoxvirus with special reference to its adaptation in primary cell cultures and its characterization
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Date
2006-08
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G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand)
Abstract
Fowlpox is an economically important and widespread disease of poultry that causes heavy morbidity and mortality in the affected birds resulting in heavy losses in the form of low egg and meat production. It affects the birds of all age, sex and breeds. The disease is caused by Avipoxvirus of the family Poxviridae. The disease is manifested in three different clinical forms–cutaneous, diphtheritic and oculo nasal forms. The mucosal lesions involving the mouth, esophagus and trachea can be confused with other respiratory diseases like infectious laryngotrachaetis, coryza etc. Keeping in view the economic impact of disease on poultry industry, the present study was undertaken to adapt the vaccine strain of FPV in chorioallantoic membrane, chicken embryo fibroblast cell culture as well as in chicken kidney cell culture and evaluate the various serological tests for rapid diagnosis of FPV infection.
Fowlpoxvirus was successfully adapted to CAM, CEF and CK cells. Characteristic pock lesions on CAM and CPE in unstained and stained preparations confirmed the presence of virus. In MGG staining, the cytopathic changes were characterized by rounding of cells 12 hrs PI and the cytoplasmic vacuolation and syncytia formation by 18 hrs PI. In few cells, the nucleus occupied eccentric position and degenerative changes in the nucleus were characterized by fragmentation of nuclear membrane in the infected CEF cells, while the cytopathic changes in infected CK cells were characterized by rounding of cells 36 hrs PI and the cytoplasmic vacuolation and syncytia formation by 48 hrs PI. The infectivity titre was calculated to be log107.14 EID50/ml on CAM and log10 9.25TCID50/ml in CEF cell culture.
The agar gel immunodiffusion test revealed the precipitation band, which confirms the presence of antigen and antibody. The serum neutralization test using the beta (constant virus serum dilution) procedure, revealed an antibody titre of 1:160.
CIE showed a precipitation line within one hr of electrophoretic run. The indirect fluorescent antibody technique (IFAT) demonstrated the presence of virus in infected cell culture. The infected embryonic chicken kidney cells as well as the infected chicken embryo fibroblast cells revealed small particulate fluorescence in the cytoplasm of the infected cells.
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