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-ß. 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-ß. 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-ß 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-ß. 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.
Subject(s)
Avian Leukosis Virus/physiology , Chickens , Interferon-Induced Helicase, IFIH1/metabolism , Transcription Factors/metabolism , Tripartite Motif Proteins/metabolism , Ubiquitin-Protein Ligases/metabolism , Animals , Avian Leukosis Virus/classification , Cell Line , Gene Expression Regulation/immunology , Gene Knockdown Techniques , Interferon-Induced Helicase, IFIH1/genetics , Interferon-beta/genetics , Interferon-beta/metabolism , RNA, Messenger/genetics , RNA, Messenger/metabolism , Transcription Factors/genetics , Tripartite Motif Proteins/genetics , Ubiquitin-Protein Ligases/genetics , Up-Regulation , Virus ReplicationABSTRACT
To identify if any exogenous avian leukosis virus (ALV) exists in a live vaccine of poultry according to the directives of the Ministry of Agriculture of the People's Republic of China, a live vaccine strain of the Newcastle disease virus (NDV) was neutralized using an anti-NDV antibody, and was subsequently used to inoculate DF-1 cells to investigate the presence of exogenous ALV. The DF-1 cells were cultured for 21 d and subsequently screened using an ELISA for the p27 antigen of the ALV. An exogenous ALV, designated ALV-NDVP4, was identified. The nucleotide sequence of the gp85 gene of the ALV-NDVP4 was compared with those of the various subgroups of the ALV. The amino acid sequence identities for the predicted gp85 of the ALV-NDVP4 and those of the ALV reference strains ranged from 88.2 to 99.5% for the 12 of the subgroup A strains of ALV (ALV-A) and from 82.7 to 87.4% for the B, C, D, and E subgroup strains. The amino acid sequence identities for the gp85 of the ALV-NDVP4 and those of the subgroup J reference strains ranged from 48.7 to 49.9%. The ALV-NDVP4 shared the highest level of homology with the SDAU09C3 strain of ALV-A, which was isolated in China, suggesting a common origin. This is the first report of ALV-A contamination in a live vaccine for poultry in China. Our findings highlight the need for improved monitoring methods for poultry vaccine production.