DENV NS1 directly induces platelet activation in a dose- and time-dependent manner.

(A) Platelets were treated with BSA or DENV NS1 recombinant proteins (10 μg/ml) for the indicated time (n = 3). (B) Platelets were treated with different concentrations of DENV NS1 recombinant proteins for 1 h (n = 3). (C) Platelets were treated with BSA or DENV NS1 (10 μg/ml) (cotreated with or without 25 μg/ml anti-NS1 specific antibodies F(ab’)2 fragment, 33D2 F(ab’)2, or the isotype-matched mouse antibodies F(ab’)2 and cmIgG F(ab’)2) for 1 h (n = 3). (D) Platelets were treated with BSA or DENV1-4 NS1 (10 μg/ml) for 1 h (n = 3). The percent fluorescence of P-selectin surface expression on platelets was analyzed by FACSCalibur flow cytometry. ***P<0.001; unpaired t-test (panels A and B), Kruskal-Wallis ANOVA (panels C and D).