Functional characterization of the IFN-γ protein in mediating antiviral defence against Newcastle disease Virus in Larus ridibundus

Introduction Newcastle disease virus (NDV) can spread across regions via migratory wild birds, posing potential threats to livestock breeding and public health security. Systematic information on the genetic characteristics, immunoregulatory functions, and antiviral activity of IFN-γ in the migratory wild bird Larus ridibundus remains limited. Methods In this study, the complete coding sequence of L. ridibundus IFN-γ was cloned and analyzed bioinformatically. A prokaryotic expression system was used to produce purified recombinant IFN-γ, and specific polyclonal antibodies were prepared for protein identification. Peripheral blood lymphocytes were exposed to graded NDV doses, serial concentrations of recombinant IFN-γ, or combined IFN-γ and NDV treatment. Quantitative real-time PCR was used to measure NDV NP transcripts and the transcription of TLR7, MyD88, IRF7, IFN-α, IFN-γ, and Mx. Results NDV infection was associated with increased transcription of TLR7 pathway-related genes. Among the tested IFN-γ concentrations, 200 ng/mL produced the strongest TLR7 transcriptional response. IFN-γ intervention significantly reduced intracellular NDV NP transcript abundance, and this reduction coincided with lower transcription of TLR7 pathway-related genes under combined treatment. Discussion These findings indicate that L. ridibundus IFN-γ has in vitro anti-NDV activity and that this activity is associated with transcriptional modulation of the TLR7-MyD88-IRF7 pathway. Direct pathway dependence remains to be established by pathway-inhibition experiments.