∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙∙ 35 J. Biol. Today's World. 2016 Feb; 5 (2): 35-39 J o u r n a l o f B i o l o g y a n d T o d a y ' s W o r l d ISSN 2322-3308 J o u r n a l h o m e p a g e : h t t p : / / j o u r n a l s . l e x i s p u b l i s h e r . c o m / j b t w Received: 20 January 2016  Accepted: 27 February 2016 Short. C doi:10.15412/J.JBTW.01050202 Interaction of embryonic chicken lung cell with different strains of infectious laryngotracheitis virus infections Mohammad Bagher Ghadiri 1 , Shahla Shahsavandi 1* , Gholam Ali Moradli 2 , Zahra Jamshidi-Navroud 1 1 Razi Vaccine & Serum Research Institute, Karaj, Iran 2 Saveh Azad University, Dr Beheshti Blv., Saveh, Iran *Correspondence should be addressed to Shahla Shahsavandi, Razi Vaccine & Serum Research Institute, Karaj, Iran; Tell: +982634570038; Fax: +982634552194; Email: s.shahsavandi@rvsri.ac.ir. ABSTRACT 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. Key words: Infectious laryngotracheitis virus, embryonic chicken lung cell, cyclophilin A, factor X Copyright © 2016 Mohammad Bagher Ghadiri et al. This is an open access paper distributed under the Creative Commons Attribution License. 1. INTRODUCTION nfectious laryngotracheitis virus (ILTV) is an economically significant avian pathogen prevented by attenuated live vaccines. ILTV belongs to the genus Iltovirus of Herpesviridae has a linear double stranded DNA genome consist of a unique long region and a unique short region which flanked by two inverted repeats (1). Entry of the virus into respiratory cells and mucosa depends upon host cell surface receptors and viral surface glycoproteins. The viral nucleocapsid is released into the cytoplasm and migrated into the nucleus following fusion of the viral envelope to the cell membrane (2, 3). ILTV genome replication and transcription seems to be similar to other alpha-herpesvirus. Three classes of genes include immediate early, early, and late genes are expressed during transcription of ILTV DNA. The immediate-early gene, infected cell polypeptide 4 (ICP4), has regulatory functions and involve in the cascade transactivation of other genes (4, 5). After assembly of viral particles, the enveloped virions are released by cell lysis. ILTV strains are propagated efficiently in embryonated chicken egg and primary cell culture derived from the embryo tissues (1, 6). The viruses can further diagnose using serological test including fluorescent antibody technique, indirect immunofluorescence, serum neutralization, and agar gel immunodiffusion which are less sensitive and laborious. Molecular techniques are preferred for rapid for detection and quantitation of ILTV DNA in clinical samples especially when the virus established lifelong latency state in trigeminal ganglia (7-10). Reversion of virulence after reactivation of the latent virus and evident of possible I