Comparative analysis of signature genes in PRRSV-infected porcine monocyte-derived cells at differential activation statuses

Authors: Miller, Laura; FLEMING, DAMARIUS - Oak Ridge Institute For Science And Education (ORISE); LI, XIANGDONG - Collaborator; Bayles, Darrell; BLECHA, FRANK - Kansas State University; SANG, YONGMING - Kansas State University

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/6/2017
Publication Date: 7/20/2017
Citation: Miller, L.C., Fleming, D.S., Li, X., Bayles, D.O., Blecha, F., Sang, Y. 2017. Comparative analysis of signature genes in PRRSV-infected porcine monocyte-derived cells to different stimuli. PLoS One. 12(7):e0181256. https://doi.org/10.1371/journal.pone.0181256.
DOI: https://doi.org/10.1371/journal.pone.0181256

Interpretive Summary: Infectious diseases cause significant economic loss to US pork producers. Although treating sick animals can help reduce this loss, prevention of disease is the first choice. The best method to prevent transmission of a livestock disease is to induce a protective immune response in susceptible animals through vaccination. For some diseases, current technology is adequate for producing safe and efficacious vaccines. However, for other diseases, vaccines produced from current technology are not adequate. In these cases, understanding the complex nature of the protective immune response may be critical to improving vaccines which requires basic research into how the immune system functions. One important part of the immune response is the activation of different types of cells within the animal's immune system. Monocytic cells are one of these cell types that are intricately involved in the animal's response to disease. They have a role in the innate responses as well as in development and maintenance of adaptive immunity against invading pathogens. Following infection, the monocytic cell becomes activated which can occur by direct contact with an infectious agent, or indirectly through stimulation of the cell by specific proteins produced by other cells in the body. Activated monocytic cells become polarized meaning the cell has developed a certain response against a virus or bacteria. Here, through examination of porcine reproductive and respiratory syndrome virus (PRRSV) infection, targeting on monocytic cells, we elaborate the direct involvement of polarization during infection. Comprehensive understanding of the immunological impact may become increasingly important to understand host-virus interactions of existing and emerging pathogens, with application to the development of novel therapies and vaccine strategies.

Technical Abstract: Activation statuses of monocytic cells are critically important for antiviral immunity. Devastating viruses like porcine reproductive and respiratory syndrome virus (PRRSV) are capable of directly infecting these cells, subverting host immunity. Monocyte-derived DCs (mDCs) are major target cells in PRRSV pathogenesis; however, the plasticity of mDCs in response to activation stimuli and PRRSV infection remains unstudied. In this study, we polarized mDCs, and applied genome-wide transcriptomic analysis and protein-protein network interaction predictions to compare signature genes involved in mDCs activation and response to PRRSV infection. Our long-term goal is to integrate activation status with antiviral responses in these cells and functionally modulate them for a prototypic cellular adjuvant/vaccine, ideal for potentiating antiviral immunity. Porcine mDCs were polarized with mediators for 30 hours, then mock-infected, infected with PRRSV strain VR2332, or a highly pathogenic PRRSV strain (rJXwn06), for 5 h. Total RNA was extracted and used to construct sequencing libraries for RNA-Seq. Comparisons were made between each polarized and unpolarized group (i.e. mediator vs. PBS), and between PRRSV-infected and uninfected cells stimulated with the same mediator. Differentially expressed genes (DEG) from the comparisons were used for prediction of interaction networks affected by the viruses and mediators. The results showed that PRRSV infection inhibited M1 immune activity and downregulated genes and predicted network interactions related to cellular integrity and inflammatory signaling. Additionally, the magnitude of DEG profiles and predicted network interactions detected in HP-PRRSV infected mDCs compared to VR-2332 infected mDCs was consistent with increased pathogenicity of the HP-PRRSV in vivo.