Saturable Dengue virus-platelet binding. Purified DENV2 was incubated with a constant number of platelets (5 × 10⁵/mL) for 1 hour and then washed 3 times with PBS. Platelet-associated virus was quantified by qRT-PCR. Surface-bound virus (open squares) was determined by subtracting the virus remaining bound after trypsinization from the total virus associated with platelets before trypsin treatment (filled squares). The binding curves were iteratively fit to a simple rectangular hyperbolic model, which represents a single global class of binding (n = 3, ± standard deviation [SD], smaller than the size of symbols). Inset: Antigenic confirmation of DENV2-platelet binding. Purified DENV2 (5 × 10⁵ particles/mL) was added to purified platelets (5 × 10⁵/mL) and incubated at (A) 4°C, (B) 25°C, or (C) 37°C. Platelets were washed in PBS 3 times. The pellet was solubilized, subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis (5% to 20% polyacrylamide), and analyzed for viral E protein antigen. The ∼61 kDa monomeric band was quantified by densitometry post- (filled squares) and preinoculation (open squares). The fit of data is arbitrary. A representative western blot is provided.