Temporal regulation of HTLV-2 expression in infected cell lines and patients: evidence for distinct expression kinetics with nuclear accumulation of APH-2 mRNA.

BACKGROUND: Human T-cell leukemia virus types 1 and 2 (HTLV-1 and HTLV-2) are delta retroviruses with similar genetic organization. Although both viruses immortalize T-cells in vitro, they exhibit distinct pathogenic potential in vivo. To search for possible differences in its expression strategy with respect to HTLV-1, we investigated the pattern of HTLV-2 expression in infected cell lines and peripheral blood mononuclear cells (PBMCs) from infected patients using splice site-specific quantitative RT-PCR. FINDINGS: A novel alternative splice acceptor site for exon 2 was identified; its usage in env transcripts was found to be subtype-specific. Time-course analysis revealed a two-phase expression kinetics in an infected cell line and in PBMCs of two of the three patients examined; this pattern was reminiscent of HTLV-1. In addition, the minus-strand APH2 transcript was mainly detected in the nucleus, a feature that was similar to its HTLV-1 orthologue HBZ. In contrast to HTLV-1, expression of the mRNA encoding the main regulatory proteins Tax and Rex and that of the mRNAs encoding the p28 and truncated Rex inhibitors is skewed towards p28/truncated Rex inhibitors in HTLV-2. CONCLUSION: Our data suggest a general converging pattern of expression of HTLV-2 and HTLV-1 and highlight peculiar differences in the expression of regulatory proteins that might influence the pathobiology of these viruses.

PTX3 predicts severe disease in febrile patients at the emergency department.

OBJECTIVES: The long pentraxin PTX3 is a promising marker of disease severity in severely ill patients. In order to identify patients warranting critical care as quickly as possible, we investigated the value of PTX3 as a biomarker for disease severity in patients presenting with fever at the emergency department. METHODS: Levels of PTX3 were measured in 211 febrile patients at the emergency and the levels were linked to markers of disease severity including admittance to a special care unit, bloodstream infection and congestive heart failure. RESULTS: In comparison to median baseline levels of 2.30 ng/ml (interquartile range 1.66-3.67 ng/ml), levels of PTX3 were significantly elevated in patients admitted to the intensive-/medium care unit (median value 44.4 ng/ml, interquartile range 13.6-105.9 ng/ml) and in patients referred to the ward (median value 14.2 ng/ml, interquartile range 7.01-25.1 ng/ml). In addition, PTX3 was associated with duration of hospital stay and acute congestive heart failure. The levels were predictive for bloodstream infection (AUC=0.71; 95% CI 0.62-0.81). CONCLUSIONS: PTX3 may be a useful marker for differentiation of patients with severe disease in patients presenting with fever to the emergency department.

The soluble pattern recognition receptor pentraxin-3 in innate immunity, inflammation and fertility.

The innate immune system consists of a cellular and a humoral arm. Components of humoral immunity include diverse molecular families, which represent functional ancestors of antibodies. They play key roles as effectors and modulators of innate resistance and inflammation. The long pentraxin PTX3 represents a prototype humoral effector molecule. Gene targeting of this evolutionarily conserved long pentraxin has unequivocally defined its role at the crossroads of innate immunity, inflammation, matrix deposition and female fertility. Here, we will review the studies on PTX3, which emphasize its role as a multifunctional soluble pattern recognition receptor acting as a non-redundant component of the humoral arm of innate immunity involved in fine-tuning inflammation, matrix deposition, angiogenesis and, in particular, in female fertility.

Coregulation in human leukocytes of the long pentraxin PTX3 and TSG-6.

The prototypic long PTX3 is a multifunctional protein involved in innate resistance to pathogens and in controlling inflammation. TSG-6 is a hyaluronan-binding protein that is involved in ECM remodeling and has anti-inflammatory and chondroprotective functions. PTX3 and TSG-6 are coregulated by growth differentiation factor-9 in granulosa cells, where they are produced during the periovulatory period and play essential roles in the incorporation of hyaluronan into the ECM during cumulus expansion. The present study was designed to assess whether PTX3 and TSG-6 are coregulated in leukocytes, in particular, in phagocytes and DC. Monocytes, macrophages, and myeloid DC were found to produce high levels of TSG-6 and PTX3 in response to proinflammatory mediators (LPS or cytokines). Unstimulated neutrophil polymorphonuclear granulocytes expressed high levels of TSG-6 mRNA, but not PTX3 transcript, and stored both proteins in granules. In contrast, endothelial cells expressed substantial amounts of PTX3 mRNA and low levels of TSG-6 transcript under the conditions tested. Anti-inflammatory cytokines, such as IL-4, dampened LPS-induced TSG-6 and PTX3 expression. Divergent effects were observed with IL-10, which synergizes with TLR-mediated PTX3 induction but inhibits LPS-induced TSG-6 transcription. Immunohistochemical analysis confirms the colocalization of the two proteins in inflammatory infiltrates and in endothelial cells of inflamed tissues. Thus, here we show that myelomonocytic cells and MoDC are a major source of TSG-6 and that PTX3 and TSG-6 are coregulated under most of the conditions tested. The coordinated expression of PTX3 and TSG-6 may play a role in ECM remodeling at sites of inflammation.

The long pentraxin PTX3 as a prototypic humoral pattern recognition receptor: interplay with cellular innate immunity.

The innate immune system consists of a cellular arm and a humoral arm. Components of humoral immunity include diverse molecular families, which represent functional ancestors of antibodies. They play a key role as effectors and modulators of innate resistance in animals and humans, interacting with cellular innate immunity. The prototypic long pentraxin, pentraxin 3 (PTX3), represents a case in point of this interplay. Gene targeting of this evolutionarily conserved long pentraxin has unequivocally defined its role at the crossroads of innate immunity, inflammation, matrix deposition, and female fertility. Phagocytes represent a key source of this fluid-phase pattern recognition receptor, which, in turn, facilitates microbial recognition by phagocytes acting as an opsonin. Moreover, PTX3 has modulatory functions on innate immunity and inflammation. Here, we review the studies on PTX3 which emphasize the complexity and complementarity of the crosstalk between the cellular and humoral arms of innate immunity.

Complement dependent amplification of the innate response to a cognate microbial ligand by the long pentraxin PTX3.

The long pentraxin PTX3 is a fluid-phase pattern recognition receptor, which plays a nonredundant role in resistance against selected pathogens. PTX3 has properties similar to Abs; its production is induced by pathogen recognition, it recognizes microbial moieties, activates complement, and facilitates cellular recognition by phagocytes. The mechanisms responsible for the effector function of PTX3 in vivo have not been elucidated. OmpA, a major outer membrane protein of Gram-negative Enterobacteriaceae, is a microbial moiety recognized by PTX3. In the air pouch model, KpOmpA induces an inflammatory response, which is amplified by coadministration of PTX3 in terms of leukocyte recruitment and proinflammatory cytokine production. PTX3 did not affect the inflammatory response to LPS, a microbial moiety not recognized by PTX3. As PTX3 binds to C1q and modulates the activation of the complement cascade, we assessed the involvement of complement in the amplification of the response elicited by KpOmpA and PTX3. Experiments performed using cobra venom factor, C1-esterase inhibitor, and soluble complement receptor 1 indicate that PTX3 amplifies the inflammatory response to KpOmpA through complement activation. The results reported here demonstrate that PTX3 activates a complement-dependent humoral amplification loop of the innate response to a microbial ligand.

Expression of the class A macrophage scavenger receptor on specific subpopulations of murine dendritic cells limits their endotoxin response.

Dendritic cells (DC) function at the interface of innate and acquired immunity and are uniquely sensitive to specific stimuli. Pattern recognition receptors (PRR) on these cells are critically important because of their ability to recognise and initiate responses to conserved microbial-associated molecular signatures. With the exception of Toll-like receptors (TLR), we know relatively little about the specific distribution of other PRR amongst populations of DC. Here, we describe the expression of the murine class A macrophage scavenger receptor (SR-A) and show that it is restricted to specific subpopulations of bone marrow-derived and splenic DC. Importantly, we demonstrate that the receptor significantly alters the response of DC to endotoxin. In contrast to the activities of other PRR that have so far been examined, uniquely SR-A limits the maturation response; SR-A-/- cells display enhanced CD40 expression and TNF-alpha production. We discuss the potential contributions of SR-A to DC biology in the context of the known multiple activities of this receptor.

The long pentraxin PTX3 as a link among innate immunity, inflammation, and female fertility.

The long pentraxin 3 (PTX3) is member of a complex superfamily of multifunctional proteins characterized by a cyclic multimeric structure. PTX3 is highly conserved in evolution and is produced by innate-immunity cells in response to proinflammatory signals and Toll-like receptor engagement. PTX3 plays complex, nonredundant functions in vivo, acting as a predecessor of antibodies, recognizing microbes, activating complement, facilitating pathogen recognition by phagocytes, and hence, playing a nonredundant role in resistance against selected pathogens. In addition, PTX3 is essential in female fertility by acting as a nodal point for the assembly of the cumulus oophorus hyaluronan-rich extracellular matrix. Thus, the prototypic long pentraxin PTX3 is a multifunctional, soluble pattern recognition receptor acting as a nonredundant component of the humoral arm of innate immunity and involved in matrix deposition and female fertility.

Pentraxins in innate immunity and inflammation.

C-reactive protein, the first innate immunity receptor identified, and serum amyloid P component are classic short pentraxins produced in the liver. Long pentraxins, the prototype of which is PTX3, are expressed in a variety of tissues. PTX3 is produced by a variety of cells and tissues, most notably dendritic cells and macrophages, in response to TLR engagement and inflammatory cytokines. PTX3 acts as a functional ancestor of antibodies, recognizing microbes, activating complement, facilitating pathogen recognition by phagocytes, hence playing a non-redundant role in resistance against selected pathogens, in particular in the lung. Thus, the prototypic long pentraxin PTX3 is a multifunctional soluble pattern recognition receptor at the crossroads between innate immunity, inflammation, matrix deposition and female fertility.

The class A macrophage scavenger receptor attenuates CXC chemokine production and the early infiltration of neutrophils in sterile peritonitis.

The macrophage scavenger receptor (SR-A) is a multifunctional receptor that is associated with several important pathological conditions, including atherosclerosis. In this study, we show, using a sterile peritonitis model, that it can regulate the inflammatory response. SR-A null mice display an increased initial granulocytic infiltration because of overproduction of the CXC chemokines, MIP-2 and keratinocyte-derived cytokine. This differential response is dependent upon particle internalization and can be mimicked by advanced glycation end product-BSA-conjugated latex beads. Thus SR-A is a nonactivating receptor, which is the first example of a pattern recognition receptor that serves to counter the activities of proinflammatory receptors and attenuates the production of specific chemokines to ensure an inflammatory response of the appropriate magnitude.