Severe acute respiratory syndrome (SARS) is a recently discovered viral disease, characterized by fever, cough, acute fibrinous pneumonia and high infectivity. Specific pathogen-free (SPF) chickens were immunized with inactivated SARS coronavirus and their eggs were harvested at regular intervals. Yolk immunoglobulin (IgY) was extracted using the water dilution method, followed by further purification on a Sephadex G-75 column. SDS-polyacrylamide gel electrophoresis (SDS-PAGE), Western blot and neutralization test results showed that the IgY obtained was of a high purity and had a strong reactive activity with a neutralization titer of 1:640. Lyophilization and stability tests showed that lyophilized anti-SARS coronavirus IgY had promising physical properties, with no significant reduction in reactive activity and good thermal stability. All these data suggest that the anti-SARS coronavirus IgY could be a new useful biological product for specific antiviral therapy against SARS.
Very virulent (vv) infectious bursal disease virus (IBDV) Gx strain with high pathogenicity was attenuated through replication in specific-pathogen-free (SPF) chicken embryos and in chicken embryo fibroblast (CEF) cell cultures. The changes in VP2 nucleotide and the deduced amino acid sequences were obtained during attenuation of vvIBDV in CEF culture. Sequence analysis of selected passages from numbers 0 to 20 in CEFs (designated here Gx to CEF-20) showed that no changes were detectable in the VP2 gene before CEF-7. There were a few changes in the nucleotide sequence of the VP2 gene but no amino acid substitutions at CEF-8. The virus of CEF-9 was an intermediate with some amino acid changes that possibly were related to virulence. CEF-10 virus had become similar to CU-1 strain. The VP2 gene sequence remained the same from CEF-10 to CEF-20. The results of pathogenicity tests showed that the mortalities of Gx, CEF-5, CEF-8, and CEF-9 in 4-wk-old SPF chickens were 64%, 60%, 60%, and 32%, respectively; whereas CEF-10, CEF-15, and CEF-20 were nonpathogenic. Virus neutralization tests with Gx strain showed that the antigenicities are similar from Gx to CEF-20.
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