In Vitro and Embryonic Evaluation of Recombinant Larus ridibundus IFN-α and Mx Proteins Against Newcastle Disease Virus

Newcastle disease virus (NDV) is an important avian pathogen that can circulate in migratory birds, including Larus ridibundus. This study examined the transcriptional responses and anti-NDV activities associated with recombinant IFN-α and Mx proteins from L. ridibundus. The IFN-α and Mx open reading frames were cloned (GenBank: OP263971 and OP263970), expressed using a pET32a(+)/E. coli system, and assessed using chicken embryos, DF-1 cells, and primary gull lymphocytes. qRT-PCR analysis showed that NDV infection increased IFN-α and Mx transcript abundance in gull lymphocytes, with peak levels at 48 h post-infection (p < 0.01). In chicken embryos, recombinant IFN-α was associated with higher embryo survival and lower NDV NP transcript abundance than recombinant Mx under the tested conditions. In DF-1 cells and primary gull lymphocytes, 0.25 mg/mL recombinant IFN-α was associated with reduced NDV NP transcript abundance, and morphological inspection suggested less severe cytopathic effects in DF-1 cells. IFN-α treatment was also accompanied by lower transcription of TLR7, MyD88, IRF7, and Mx compared with the NDV group at 48 h. These data support a role for gull IFN-α in limiting NDV-associated transcriptional responses in vitro, while further protein-level and infectious-virus assays are required to define the underlying mechanism.