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Currently, a variety of immunostimulatory molecules are used as adjuvants in combination with poor immunogenic recombinant infectious bursal disease virus (IBDV) vaccine antigen. TIR domain of Toll-like receptors (TLRs) triggers the interleukin-1 (IL-1) signaling cascade which plays a critical role in immune responses against infectious agents. For this study, the bacmid DNA pBac-VP2 of a field isolate was generated and transfected to Sf9 insect cells to produce recombinant VP2 (rVP2). In addition, based on in silico analysis, the cDNA encoding the conserved TIR domain of TLR7 (TIR-TLR7) contain the IL-1 receptor was synthesized and used as an adjuvant. We further evaluated the ability of rVP2/TIR-TLR7 vaccine candidate to induce specific immune responses in specific pathogen-free (SPF) chickens and compared the efficacy by challenging with the virulent IBDV. The results indicate that rVP2/TIR-TLR7-adjuvanted vaccine elicited humoral immune responses and protected chickens against IBDV infection. Higher levels of neutralizing IBDV antibody titers were observed in chickens intramuscularly immunized with rVP2/TIR-TLR7 than those injected with rVP2 alone. The antibody titers were higher in chickens which received booster injection. Furthermore, chickens immunized with rVP2/TIR-TLR7 in the prime and boost groups had significant protection against a virus challenge. The survival rate was 70 and 90% after the primary and booster rVP2/TIR-TLR7 vaccinations, respectively, and indicated that they were protected from virus challenge. Despite the unvaccinated control group, the immunized chickens with rVP2/TIR-TLR7 did not show any clinical signs and histopathological changes of the bursa. Our results demonstrate that TIR-TLR7 is a potential vaccine adjuvant and can induce antigen-specific immune responses induced by rVP2 for protection against IBDV infection. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]