thromboplastin and Herpes-Simplex

Essentials The coagulation initiator, tissue factor (TF), is on the herpes simplex virus 1 (HSV1) surface. HSV1 surface TF was examined in mice as an antiviral target since it enhances infection in vitro. HSV1 surface TF facilitated infection of all organs evaluated and anticoagulants were antiviral. Protease activated receptor 2 inhibited infection in vivo and its pre-activation was antiviral. SUMMARY: Background Tissue factor (TF) is the essential cell surface initiator of coagulation, and mediates cell signaling through protease-activated receptor (PAR) 2. Having a diverse cellular distribution, TF is involved in many biological pathways and pathologies. Our earlier work identified host cell-derived TF on the envelope covering several viruses, and showed its involvement in enhanced cell infection in vitro. Objective In the current study, we evaluated the in vivo effects of virus surface TF on infection and on the related modulator of infection PAR2. Methods With the use of herpes simplex virus type 1 (HSV1) as a model enveloped virus, purified HSV1 was generated with or without envelope TF through propagation in a TF-inducible cell line. Infection was studied after intravenous inoculation of BALB/c, C57BL/6J or C57BL/6J PAR2 knockout mice with 5 × 10

Topics: Animals; Anticoagulants; Antiviral Agents; Disease Models, Animal; Female; Herpes Simplex; Herpesvirus 1, Human; Host-Pathogen Interactions; Injections, Intravenous; Mice, Inbred BALB C; Mice, Inbred C57BL; Mice, Knockout; Receptor, PAR-2; Th1 Cells; Thromboplastin; Viral Envelope Proteins

The coagulation system provides physiologic host defense, but it can also be exploited by pathogens for infection. On the HSV1 surface, host-cell-derived tissue factor (TF) and virus-encoded glycoprotein C (gC) can stimulate protease activated receptor 1 (PAR1)-enhanced infection by triggering thrombin production. Using novel engineered HSV1 variants deficient in either TF and/or gC, in the present study, we show that activated coagulation factors X (FXa) or VII (FVIIa) directly affect HSV1 infection of human umbilical vein endothelial cells in a manner that is dependent on viral TF and gC. The combination of FXa and FVIIa maximally enhanced infection for TF(+)/gC(+) HSV1 and receptor desensitization and Ab inhibition demonstrated that both proteases act on PAR2. Inhibitory TF Abs showed that the required TF source was viral. Individually, TF or gC partly enhanced the effect of FXa, but not FVIIa, revealing gC as a novel PAR2 cofactor for FVIIa. In sharp contrast, thrombin enhanced infection via PAR1 independently of viral TF and gC. Thrombin combined with FXa/FVIIa enhanced infection, suggesting that PAR1 and PAR2 are independently involved in virus propagation. These results show that HSV1 surface cofactors promote cellular PAR2-mediated infection, indicating a novel mode by which pathogens exploit the initiation phase of the host hemostatic system.

Topics: Antigens, Surface; Antigens, Viral; Blood Coagulation Factors; Cells, Cultured; Coenzymes; Disease Progression; Herpes Simplex; Host-Pathogen Interactions; Human Umbilical Vein Endothelial Cells; Humans; Receptor, PAR-2; Signal Transduction; Thromboplastin; Viral Envelope Proteins

Herpes simplex virus (HSV)-infected endothelium is a model for vascular injury and possibly the development of atherosclerosis. In vitro infection of human umbilical vein endothelial cells (HUVEC) by HSV-1 results in a number of changes including the expression of a procoagulant activity (PCA) compatible with that due to tissue factor (TF) synthesis. In this study, we have further characterized this PCA using more stringent assays for TF, and examined whether virus rendered incapable of replication retains the ability to stimulate TF synthesis in HUVEC.. Confluent monolayers of HUVEC were exposed to intact or ultraviolet/heat-inactivated HSV-1. At appropriate time intervals, TF PCA was assessed by clotting assays, and TF antigen by an enzyme-linked immunosorbent assay specific for TF. The appearance of mRNA specific for TF was performed by Northern blotting.. TF activity was demonstrated by both 1-stage and 2-stage clotting assays; the dependence of the latter on factor VIIa, and the inhibition by specific blocking antibodies to human TF support the notion that the PCA is indeed due to TF. Furthermore, cellular TF antigen levels were found to parallel TF activity, and there was a transient de novo expression of TF mRNA. Tissue factor PCA in HSV-infected HUVEC remained "encrypted"; that is, full clotting activity was not expressed in the absence of cellular disruption in a situation analogous to that seen in all normal cells thus far examined that express TF PCA. However, this response did not appear to be dependent upon replicative infection of HSV-1 within the endothelial cell since a similar (although lesser) induction of TF PCA was present in cells that had been exposed to virus previously rendered incapable of replication.. HSV-1 induces PCA in HUVEC which is clearly TF-dependent; this response does not require viral replication. These data indicate increased complexity in HSV interactions with vascular endothelium and imply induction of some procoagulant functions by nonproductive infection.

Topics: Blood Coagulation Factors; Cells, Cultured; Endothelium, Vascular; Herpes Simplex; Humans; Simplexvirus; Thromboplastin; Umbilical Veins; Virus Replication

Atherosclerotic lesions have been reported to contain herpes simplex virus 1 (HSV-1) genomic material. This, and other previous evidence, suggests that latent viral infection may be an atherogenic trigger. Moreover, active HSV-1 lesions manifest marked fibrin deposition in microvessels. In this report we show that very early infection of human endothelial cells with HSV-1 appears to alter surface conformation as detected by merocyanine 540 staining. Concomitantly, the efficiency of prothrombinase complex assembly increases, resulting in a 2- to 3-fold accelerated rate of thrombin generation on the cell surface. Increased thrombin generation is probably doubly procoagulant, since we also demonstrate that thrombin-induced platelet accumulation on HSV-infected endothelium (50.7 +/- 9.3%) is increased compared to uninfected endothelium (9.5 +/- 2.1%; P less than 0.002). Associated with HSV infection, prostacyclin secretion in response to thrombin is diminished by a factor of 20, probably explaining the enhanced platelet attachment. We conclude that HSV infection shifts endothelial cell properties from anticoagulant to procoagulant, both by promoting prothrombinase complex formation and function and by increasing platelet binding, well before cell disruption takes place. Virus-induced changes in the endothelial plasma membrane and diminished prostacyclin secretion are suggested as the pathways for this pathophysiologic mechanism, which may be germane to atherosclerotic thrombosis as well as HSV-mediated tissue necrosis.

Topics: Arteriosclerosis; Blood Platelets; Cell Adhesion; Cell Aggregation; Endothelium; Herpes Simplex; Humans; Indomethacin; Pyrimidinones; Simplexvirus; Thrombin; Thromboplastin