Examining responses of chicken embryonic neural stem cell to infectious laryngotracheitis virus infections

Infectious laryngotracheitis virus (ILTV) infection causes economic losses in the poultry industry. Outbreaks of the infection in commercial poultry are controlled by using attenuated live vaccines. The genomic and antigenic characteristics between virulent and vaccine strains of ILTV are very similar, thus the differential diagnosis of ILTV strains is targeted in controlling programs. Here, the chicken embryonic neural stem (cENS) cell serves as a host model to study virulence characteristics of ILTVs. The susceptibility of cENS cells to different ILTV strains infection was investigated by analyzing the impact of infection on cell death, virus latency, and determining the host cell responses. We found that cENS cells are highly susceptible to vaccine strain ILTV infection. Upon infection, the strain showed faster replication kinetics in cell culture and marked cytopathic effects with affecting the expression of cellular neuropeptide Y (NPY). Virulent strain was able to enter cENS cells, but no infectious virus was produced at third passage. The establishment of latency state was confirmed by molecular detection of viral ICP4 gene and virus reactivation assay. In contrast to vaccine strain, transcription level of cellular NPY was also upregulated significantly following virulent strain infection. The difference expression pattern of NPY in ILTV strains-infected cells is most closely with the presence of CPE in culture. The neural stem cell system may provide the most relevant tool for differential diagnosis of ILTV strains.