Inhibitory effect of transfer factor on infection with the novel variant strain of infectious bursal disease virus in chickens.

The novel variant strain of infectious bursal disease virus (nVarIBDV) has emerged as one of the immunosuppressive viruses severely threatening the poultry industry. Even with the presence of certain levels of maternal antibodies in some flocks, infection with nVarIBDV cannot be prevented. Non-specific immunostimulants are wildely used in clinical practice to enhance the prevention and control of this disease. To explore the potential of chicken transfer factor (TF) in suppressing nVarIBDV infection,a total of 210 SPF chicks were randomly divided into 7 groups in this study. The nVarIBDV infection was administered at two different ages (7 and 14 days post-hatch), and the TF treatment was applied at two dosage levels: low dose (0.25 mL per chick) and high dose (0.5 mL per chick). Viral load of nVarIBDV was detected via qRT-PCR at various time points, and the intervention effect of TF on nVarIBDV infection was evaluated through dynamic monitoring of body weight and analysis of bursal organ development index. The results showed that SPF chicks were infected with nVarIBDV at different ages (7 days and 14 days) significantly suppressed body weight gain and induced bursal atrophy. The application of TF could effectively alleviate the nVarIBDV-induced growth retardation and bursal atrophy, while also markedly inhibiting viral replication in the bursa of Fabricius. Moreover, the inhibitory effect was positively correlated with the dosage of TF used. This study provides a new technical supplement for improving the prevention and control of nVarIBDV, while also offering valuable insights for research on antiviral immune regulation in poultry.