C1q binds to full recombinant Envelope proteins of all Dengue Virus (DENV1-4) serotypes (A–D, respectively) but not to Bovine Serum Albumin (BSA; negative control). Within each serotype, binding of C1q occurs preferentially to the portion of ENV containing DI/II (A, B and D), except for serotype 3 (C). ELISA plates were coated with DENV ENV full length, ENV DI/II and ENV DIII (aa 1–413, aa 1–296 and aa 297–413, respectively; Table S1) fragments and BSA, and incubated with C1q concentrations ranging from 1 up to 40 µg/ml. Results obtained are representative of 5 independent experiments. Statistical analysis was done using GraphPad program and Student’s paired, 2 tails t-test. Values were considered significant when p<0.05.