Mohammad Bagher Ghadiri, Shahla Shahsavandi, Gholam Ali Moradli, Zahra Jamshidi-Navroud
"The economic losses of infectious laryngotracheitis virus (ILTV) are prevented using attenuated live vaccines. Differential diagnosis of ILTV strains is still a critical problem in controlling programs. In this study, the embryonated chicken liver cell (ECL) serves as a host model to study virulence characteristics of ILTV strains. The permissivity of ECL cells to ILTV infection was investigated by assessing susceptibility of the cells to vaccine strain and virulent strain infections, analyzing the impact of viral infection on cell viability, and determining the host cellular factor X (FX) and cyclophilin A (CypA) at three passages. To evaluate the lytic replication dynamics of ILTV in infected cells the collected suspension of last passage of each strain was inoculated onto the dropped chorio-allantoic membrane of specific pathogen free eggs then checked for observing characteristic lesions. The results indicated that ECL cells are highly susceptible to attenuated vaccine strain ILTV infection. Upon infection, the strain showed faster replication kinetics in cell culture and marked cytopathic effects. Virulent strain was able to enter ECL cells but no infectious virus was produced at 3rd passage. The establishment of latency state was not confirmed by reactivation assay. In contrast to vaccine strain, cellular FX was also traced following virulent strain infection. The difference expression pattern of FX in ILTV strains-infected cells is most closely with the presence of cytopathic effects in culture. The embryonated chicken lung cell system may potentiate the relevant tool for differential diagnosis of ILTV strains."