Fig. 3.

Biological characteristics of rL-BEFV-G in poultry. (A) Kinetics of rL-BEFV-G replication in embryonated eggs. Ten-day-old embryonated eggs were infected with rLa or rL-BEFV-G at 10⁵ TCID₅₀. Allantoic fluid of six eggs from each group was harvested at 24, 48, 72 and 96 h postinoculation, and virus titers were determined in EID₅₀ units in 10-day-old embryonated eggs. (B) Kinetics of rL-BEFV-G replication in MDBK cells. Monolayers of MDBK cells were infected with either egg-propagated rLaSota or rL-BEFV-G at an MOI of 0.01. After five washes 1 h postinfection, the cells were incubated with 100-fold-diluted mouse serum against NDV for 30 min to neutralize the residual viruses in the supernatants. After replacement of the medium with fresh medium, the infected cells were incubated at 37 °C in the absence (B) or presence (C) of TPCK trypsin (1 μg/ml). The culture supernatants were collected at different times, and their virus was titrated in MDBK cells with 1 μg of TPCK trypsin per ml. Significant differences between rLa and rL-BEFV-G were observed using Student’s t-test. *, P <0.05; **, P < 0.01. (D) Pathogenicity assay in SPF eggs and chickens. MDT, ICPI and IVPI were determined according to the recommended OIE method