Figure 1. Binding of DENV immune serum to Zika virus virions. Zika virus and 4 DENV serotypes were captured by using plate-bound mouse monoclonal antibody 4G2 and incubated with serum from donors who had had a primary DENV, secondary DENV, or primary Zika virus infection. In 2 separate experiments (A, B), serum binding was detected by using a horseradish peroxidase–conjugated human IgG. C, D) Differential global binding of each virus was accounted for by subtracting background from native human serum and normalizing to a high binding serum common to both plates (DT144). DENV, dengue virus; NHS, naive human serum; OD, optical density.