Alboserpin, the Main Salivary Anticoagulant from the Disease Vector Aedes albopictus, Displays Anti-FXa-PAR Signaling In Vitro and In Vivo.

Blood-feeding arthropods secrete potent salivary molecules, which include platelet aggregation inhibitors, vasodilators, and anticoagulants. Among these molecules, Alboserpin, the major salivary anticoagulant from the mosquito vector Aedes albopictus, is a specific inhibitor of the human coagulation factor Xa (FXa). In this study, we investigated the anti-inflammatory properties of Alboserpin, in vitro and in vivo. In vitro, Alboserpin inhibited FXa-induced protease-activated receptor (PAR)-1, PAR-2, PAR-3, VCAM, ICAM, and NF-κB gene expression in primary dermal microvascular endothelial cells. Alboserpin also prevented FXa-stimulated ERK1/2 gene expression and subsequent inflammatory cytokine release (MCP-1, TNF-α, IL-6, IL-8, IL-1ß, IL-18). In vivo, Alboserpin reduced paw edema induced by FXa and subsequent release of inflammatory cytokines (CCL2, MCP-1, IL-1α, IL-6, IL-1ß). Alboserpin also reduced FXa-induced endothelial permeability in vitro and in vivo. These findings show that Alboserpin is a potent anti-inflammatory molecule, in vivo and in vitro, and may play a significant role in blood feeding.

Identification of a substrate-like cleavage-resistant thrombin inhibitor from the saliva of the flea Xenopsylla cheopis.

The salivary glands of the flea Xenopsylla cheopis, a vector of the plague bacterium, Yersinia pestis, express proteins and peptides thought to target the hemostatic and inflammatory systems of its mammalian hosts. Past transcriptomic analyses of salivary gland tissue revealed the presence of two similar peptides (XC-42 and XC-43) having no extensive similarities to any other deposited sequences. Here we show that these peptides specifically inhibit coagulation of plasma and the amidolytic activity of α-thrombin. XC-43, the smaller of the two peptides, is a fast, tight-binding inhibitor of thrombin with a dissociation constant of less than 10 pM. XC-42 exhibits similar selectivity as well as kinetic and binding properties. The crystal structure of XC-43 in complex with thrombin shows that despite its substrate-like binding mode, XC-43 is not detectably cleaved by thrombin and that it interacts with the thrombin surface from the enzyme catalytic site through the fibrinogen-binding exosite I. The low rate of hydrolysis was verified in solution experiments with XC-43, which show the substrate to be largely intact after 2 h of incubation with thrombin at 37 °C. The low rate of XC-43 cleavage by thrombin may be attributable to specific changes in the catalytic triad observable in the crystal structure of the complex or to extensive interactions in the prime sites that may stabilize the binding of cleavage products. Based on the increased arterial occlusion time, tail bleeding time, and blood coagulation parameters in rat models of thrombosis XC-43 could be valuable as an anticoagulant.

Cryptococcosis in patients living with hepatitis C and B viruses.

Cryptococcosis, a systemic fungal infection, has become a significant, global public health problem. Patients with liver disease have an increased predisposition to infections, such as Cryptococcosis. To report the underlying disease, the variety of etiologic agents involved and the outcomes of the Cryptococcosis in patients living with HBV and/or HCV, we reviewed 34 medical records of patients who were diagnosed with Cryptococcosis by the Mycology Laboratory of Santa Casa Hospital, Porto Alegre, Brazil. Males corresponded to 79% of the patients, and the average patient age was 46.9 years. The cultures of 26/34 patients were positive: 25 patients were infected with Cryptococcus neoformans and one with C. gattii. A total of 14 deaths (41%) occurred. As a criterion of our study, all patients had viral hepatitis infection: 27 (80%) were infected with HCV, five (15%) were infected with HBV, and two patients were infected with both viruses. Because HBV and/or HCV are transmitted among drug users through infected blood, and the end-stage cirrhotic liver must be transplanted, these two population types were well represented in this study and were analyzed in detail. Cryptococcosis patients living with HCV and/or HBV appear to have the same symptoms, mean age and gender distribution as the general Cryptococcosis population. Once Cryptococcosis affects the brain, a high mortality rate ensues; therefore, physicians must be aware of the possible occurrence of this disease in patients living with HCV and HBV.