Described here is a method to produce a chimeric protein having portions of yellow fever virus and dengue virus. A small portion of the yellow fever virus 17D vaccine strain envelope protein (or other related flavivirus) can be replaced by the corresponding portion from the dengue virus envelope protein. In some embodiments the chimeric protein may be used to create a treatment composition for DENV infection. In others, the chimeric protein may be used to create a vaccine that will induce broadly protective antibodies against dengue virus and reduce the induction of non-neutralizing antibodies that will cause enhancement.