Endogenous retroviruses transcriptomes in response to four avian pathogenic microorganisms infection in chicken

Abstract

Background: Endogenous retroviruses (ERVs) are common in the genomes of vertebrates and have been implicated in a variety of host responses such as immunity, phenotypic character and disease occurrence. However, the impact of ERVs on chicken disease is not well understood. In particular, the expression profiles of chicken ERVs (ChERVs) in the infection of pathogenic microorganisms are not clear. Results: In the present study, we systematically identified 436 full-length ChERVs from the chicken genome and analyzed their neighboring genes. Subsequently, ChERV transcriptomes were analyzed in chicken after subgroup J avian leukosis virus (ALV-J), avian influenza virus (AIV), Marek’s disease virus (MDV) and avian pathogenic escherichia coli (APEC) infection. We found that about 50%-68% of ChERVs were transcriptionally active in infected-samples and uninfected-samples, although the abundance of most ChERVs is relatively low. Moreover, compared to uninfected-samples, a few ChERVs were significantly differentially expressed in ALV-J (49 ChERVs), AIV (18 ChERVs), MDV (66 ChERVs) and APEC (17 ChERVs) infected-samples. Of these differentially expressed ChERVs, only ChERV-3 was simultaneously down-regulated in the four ERV transcriptomes analysis after ALV-J, AIV, MDV and APEC infection. Further verification experiments found that both the exogenous and endogenous expression of ChERV-3 env gene was inhibited after ALV-J infection in chicken fibroblasts. However, overexpression of ChERV-3 env could induce the expression of interferon-stimulated genes (ISGs), but did not affect the replication of ALV-J.Conclusions: ChERV transcriptome was analyzed in chicken tissues after ALV-J, AIV, MDV and APEC infection. ChERV-3 was all significantly down-regulated in 4 ChERV transcriptomes after ALV-J, AIV, MDV and APEC infection. The envelope protein of ChERV-3 can induce the expression of host ISGs, but appears to have no influence on the replication of ALV-J. To our knowledge, this study is the first systematic analysis of the expression profile of chicken endogenous retroviruses after avian pathogens infection. These findings may be of significance for understanding the role and function of ChERVs to response the pathogenic microorganism infection.