Initial immunoprecipitation experiments with D29 Fab-IgG precipitated both prM and E proteins. However, upon dissociation of the prM interaction with E by the addition of SDS, only prM was precipitated by D29 Fab-IgG, pinpointing prM as the native binding target. Similarly, h3H5 only precipitated E upon addition of SDS, whereas the protein profile precipitated by h4G2 was not affected possibly due to its epitope at the fusion loop of E being occluded by the presence of prM [29, 30] , and only 'free' E proteins were pulled down in both the presence and absence of SDS.