Abstract
This study focuses on the immunoregulatory effects of chicken TRIM25 on the replication of subgroup A of avian leukosis virus (ALV-A) and the MDA5-mediated type I interferon response. The ALV-A-SDAU09C1 strain was inoculated into DF1 cells and 1-day-old SPF chickens, and the expression of TRIM25 was detected at different time points after inoculation. A recombinant overexpression plasmid containing the chicken TRIM25 gene (TRIM25-GFP) was constructed and transfected into DF1 cells to analyse the effects of the overexpression of chicken TRIM25 on the replication of ALV-A and the expression of MDA5, MAVS and IFN-β. A small interfering RNA targeting chicken TRIM25 (TRIM25-siRNA) was prepared and transfected into DF1 cells to assess the effects of the knockdown of chicken TRIM25 on the replication of ALV-A and the expression of MDA5, MAVS and IFN-β. The results showed that chicken TRIM25 was significantly upregulated at all time points both in ALV-A-infected cells and in ALV-A-infected chickens. Overexpression of chicken TRIM25 in DF1 cells dramatically decreased the antigenic titres of ALV-A in the cell supernatant and upregulated the relative expression of MDA5, MAVS and IFN-β induced by ALV-A or by poly(I:C); in contrast, knockdown of chicken TRIM25 significantly increased the antigenic titres of ALV-A and downregulated the relative expression of MDA5, MAVS and IFN-β. It can be concluded that chicken TRIM25 can inhibit the replication of ALV-A and upregulate the MDA5 receptor-mediated type I interferon response in chickens. This study can help improve the understanding of the antiviral activities of chicken TRIM25 and enrich the knowledge of antiviral responses in chickens.
Highlights
Tripartite motif 25 (TRIM25) is a tripartite motif (TRIM) protein family member and is characterized by a conserved structural domain at the N terminus, including a TRIM25 was first reported in 1993 as an oestrogenresponsive finger protein (EFP) that regulates the oestrogen response [5]
These results suggest that chicken TRIM25 might be involved in the cell responses to ALV-A infection
TRIM25 expression in chickens is significantly upregulated by ALV‐A infection To further confirm the expression of TRIM25 after ALV-A infection in vivo, 1-day-old SPF chickens were infected with the ALV-A strain, and the mRNA expression of TRIM25 in five organs, the spleen, liver, bursa, lung and kidney, was detected at 7 dpi, 14 dpi, 21 dpi and
Summary
Tripartite motif 25 (TRIM25) is a tripartite motif (TRIM) protein family member and is characterized by a conserved structural domain at the N terminus, including a TRIM25 was first reported in 1993 as an oestrogenresponsive finger protein (EFP) that regulates the oestrogen response [5]. Many animal TRIM25 genes have been cloned, and their molecular structures and antiviral effects have been reported [12, 13]. The chicken TRIM25 gene was cloned in 2015, and it was confirmed that its protein was widely expressed in chickens, especially in immune organs [14, 15]. Due to the absence of RIG-I in chickens [16, 17], little is known about the immunoregulatory effects of chicken TRIM25 on the replication of RNA viruses and type I IFN responses. In 2015, it was reported that stimulator of IFN genes (STING), as an important regulator of chicken innate immune signalling, might be involved in the MDA5 signalling pathway in chicken cells [18]. It was found that chicken TRIM25 can inhibit the replication of subgroup A avian leukosis virus (ALV-A) and upregulate the MDA5-mediated IFN-β response in chicken cells
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