Antiviral genes in the Asian swamp eel Monopterus albus: comparison of tissue expression and inducible expression of six interferon regulatory factors

Interferon regulatory factors (IRFs) play a vital role in the innate and adaptive immune system. The Asian swamp eel (Monopterus albus) is one of the most economically important freshwater fishes in China. Immunological data on the species are scare. In the present study, the expression pattern of six types of interferon regulatory factor (IRF) was studied in the Asian swamp eel. Six IRFs except IRF4 were shown to be constitutively expressed in all tissues examined. Their transcription was significantly higher in lymphoid tissues, such as intestine, skin and spleen. Furthermore, IRF1 and IRF5 was also respectively expressed at a high level in the heart and brain. However, the transcript level of IRF4 was low even undetected in most tissues. After polyinosinic- polycytidylic acid (poly I:C) treatment, the transcript levels of IRF1 and IRF4 increased, while those of IRF5 and IRF7 decreased at some time points. However, IRF2 and IRF10 did not respond to the poly I:C challenge. In addition, infection with bacterial pathogen Aermonas hydrophila and an acanthocephalan could upregulate the IRFs' expression. The results suggested that IRFs are related to the immune response to viral, bacterial and parasitic infection in Asian swamp eel, which will help to clarify the biological function of IRFs in the immune system.