Effects of Porcine Reproductive and Respiratory Syndrome Virus-Infected Antigen-Presenting Cells on T Cell Activation and Antiviral Cytokine Production

Abstract

The ability of porcine reproductive and respiratory syndrome virus (PRRSV) to suppress T cell expression of CD25 (alpha chain of interleukin [IL]-2 receptor), interferon-gamma (IFN-gamma), and tumor necrosis factor-alpha (TNF-alpha) was determined by flow cytometry in naive porcine T cells in response to mitogen (concanavalin A) and cytokine inducers (phorbol 12-myristate 13-acetate plus ionomycin [PMA/I]). Four PRRSV isolates of varying clinical virulence and three different types of porcine myeloid antigen-presenting cells (APCs) were used. T cells cultured with monocytes infected with virulent PRRSV (VR-2385, SDSU-73, and VR-2332), but not with a vaccine strain (Ingelvac PRRS MLV; Boehringer Ingelheim Vetmedica, St. Joseph, MO), demonstrated significantly reduced CD25 expression (%CD25(+)) and IFN-gamma expression (%IFN-gamma (+)) compared with T cells incubated with uninoculated monocyte cultures. T cells cultured with monocytes infected with all four PRRSV isolates demonstrated significantly reduced %TNF-alpha (+). The significant reduction of %CD25(+), %IFN-gamma (+), and %TNF-alpha (+) was not detected in T cells cultured with monocyte-derived macrophages (MDMs) and immature monocyte-derived dendritic cells (MDCs) infected with any PRRSV isolates. Heat-inactivated PRRSV did not induce significantly reduced T cell responses in any APC cultures. The reduction of T cell response in monocyte cultures was not due to PRRSV-induced T cell death. Gene expression of IL-10 detected by semiquantitative reverse transcriptase-polymerase chain reaction was significantly increased in virulent PRRSV-infected monocyte cultures after PMA/I, but not concanavalin A, stimulation compared with IL-10 gene expression from uninoculated monocyte cultures. Increased IL-10 gene expression contributed to significantly reduced %IFN-gamma (+) and %TNF-alpha (+), but not %CD25(+), as determined by IL-10 neutralization assay. This study reports that PRRSV has the ability to suppress T cell responses. The suppressive ability of PRRSV is associated with viral virulence and is mediated by virus-infected monocytes, but not by virus-infected MDMs and immature MDCs.

The N-N non-covalent domain of the nucleocapsid protein of type 2 porcine reproductive and respiratory syndrome virus enhances induction of IL-10 expression

“…IL-10 is expressed by dendritic cells (DCs) IL-10 is thought to play an important role in the immunopathogenesis of PRRSV infection (Mateu & Diaz, 2008). PRRSV infection can upregulate IL-10 expression (Charerntantanakul et al, 2006;, which causes an imbalance between proinflammatory cytokines, such as TNF-a, and impairment of the immune response in the lungs (Gó mez-Laguna et al, 2013). Transcriptional analysis of PRRSV-infected pulmonary alveolar macrophages (PAMs) revealed IL-10 upregulation at 12 h postinfection (p.i.)…”

Comparison of humoral and cellular immune responses to inactivated swine influenza virus vaccine in weaned pigs

“…The objectives of this study were to evaluate and compare the humoral and cellular responses to homologous and heterologous viruses following inactivated SIV vaccination, using standard HI assays and multi-parameter flow cytometry (MP-FCM). The MP-FCM has been well established in our laboratory to measure specific CMI responses to viral and bacterial antigens in bovine, porcine, and equine systems using 4-6 color combinations (Charerntantanakul et al, 2006a(Charerntantanakul et al, , 2006bPlatt et al, 2008Platt et al, , 2009Platt et al, , 2010aPlatt et al, , 2010b. This study reports our current porcine 6-color MP-FCM.…”

Antiviral Regulation in Porcine Monocytic Cells at Different Activation States

“…PRRSV is an enveloped positive-strand RNA virus that directly infects subsets of Ms and DCs and subverts immune responses in monocytic cells, making it ideal for deciphering how monocytic cell activation status interacts with antiviral immunity (21,(24)(25)(26)(27)(28). Monocytic cells are critical for providing early immune surveillance and bridging adaptive antiviral immunity (1-5, 7, 11).…”

“…Direct infection of monocytic subsets of Ms and DCs by PRRSV inevitably leads to immune deviation and likely alters activation statuses (21). Few studies have focused on the activation status of porcine monocytic cells or how cell activation status modulates antiviral immunity (27,28). Notably, in this study we focused on examining Gene Ontology (GO) analysis based on comparative transcriptomes revealed in macrophages at different activation statuses upon viral infection, rather than a transcriptomic comparison between infected and noninfected tissues/cells, which has been well documented in previous studies (29,30).…”