2.5 Identification of PRV isolate
Physicochemical
properties of
NY
isolate as a representative PRV strain were assayed as described
previously (Binn et al., 1970). Briefly, the NY isolate was added into
eight eppendorf tubes. Tubes 1-2 were treated by water bath at 56℃ for
60 min and chloroform at 4℃ for 30 min, respectively. Tubes 3-4 were
treated by adjusting the culture medium pH to 3.0 and 11.0 with 0.1 M
HCl/NaOH solutions, and after incubation at 37℃ for 1 h, and the pH
values were then adjusted back to 7.0. Tube 5 was digested with trypsin
at 37℃ water bath for 1.5 h, and then added 4 mL of the inactivated
fetal bovine serum to terminate the reaction. Tube 6 was incubated with
formaldehyde at 37℃ for 2 d. Tube 7 was treated under ultraviolet ray
for 30 min. Tube 8 was used as a negative control. Viruses of the eight
tubes were inoculated on ST monolayers respectively and
TCID50 were determined. In addition, the
7th passage of NY isolate
was stained with uranyl acetate and
examined using a Hitachi TEM transmission electron microscope (Hitachi,
Japan).