Elevated levels of full-length and thrombin-cleaved osteopontin during acute dengue virus infection are associated with coagulation abnormalities

Abstract

Introduction: Dengue virus (DENV) is transmitted by the mosquito vector, and causes a wide range of symptoms that lead to dengue fever (DF) or life-threatening dengue hemorrhagic fever (DHF). The host and viral correlates that contribute to DF and DHF are complex and poorly understood, but appear to be linked to inflammation and impaired coagulation. Full-length osteopontin (FL-OPN), a glycoprotein, and its activated thrombin-cleaved product, trOPN, integrate multiple immunological signals through the induction of pro-inflammatory cytokines.

Materials and method: To understand the role of OPN in DENV-infection, we assessed circulating levels of FL-OPN, trOPN, and several coagulation markers (D-dimer, thrombin-antithrombin complex [TAT], thrombomodulin [TM], and ferritin in blood obtained from 65 DENV infected patients in the critical and recovery phases of DF and DHF during a dengue virus epidemic in the Philippines in 2010.

Results: Levels of FL-OPN, trOPN, D-dimer, TAT, and TM were significantly elevated in the critical phase in both the DF and DHF groups, as compared with healthy controls. During the recovery phase, FL-OPN levels declined while trOPN levels increased dramatically in both the DF and DHF groups. FL-OPN levels were directly correlated with D-dimer and ferritin levels, while the generation of trOPN was associated with TAT levels, platelet counts, and viral RNA load.

Conclusion: Our study demonstrated the marked elevation of plasma levels of FL-OPN and thrombin-cleaved OPN product, trOPN, in DENV-infection for the first time. Further studies on the biological functions of these matricellular proteins in DENV-infection would clarify its pathogenesis.

Keywords: Coagulation; Dengue virus; Full-length osteopontin; Inflammation; Thrombin; Thrombin-cleaved osteopontin.

Figure 1. Elevated plasma full-length osteopontin (FL-OPN) and thrombin-cleaved OPN (trOPN) levels in patients infected with dengue virus

(A & B) The levels of FL-OPN (measured by the IBL ELISA kit) and trOPN differed significantly between patients with dengue fever, patients with dengue hemorrhagic fever, and healthy controls during the critical phase of dengue virus infection. The levels of FL-OPN declined in the recovery phase, while those of trOPN increased. (C) A significant inverse correlation was observed between the recovery phase OPN (measured by the IBL ELISA kit) and trOPN levels.

Figure 2. Coagulation marker levels

Plasma levels of thrombin-antithrombin complexes (TAT), and D-dimer, as well as serum levels of thrombomodulin (TM) are shown for healthy controls (HCs) and dengue virus (DENV)-infected patients during the critical (cri) and recovery (rec) phases. Ferritin levels from HCs were not measured because of a sample shortage; the reference range was 25–283 ng/ml in healthy individuals.