EVALUATION OF RECOMBINANT DENGUE VIRAL ENVELOPE-B DOMAIN PROTEIN ANTIGENS FOR THE DETECTION OF DENGUE COMPLEX-SPECIFIC ANTIBODIES

To increase the specificity of dengue (DEN) diagnosis based on antibod y detection, we have evaluated recombinant proteins as antigens that i ncorporate most of the B domain of the DEN virus envelope protein fuse d to the trpE protein of Escherichia coli (trpE-DEN). A pooled antigen consisting of trpE-DEN proteins representing all four serotypes of DE N virus was used in an indirect ELISA for the detection of IgG or IgM antibody. This assay was compared with a standard IgG indirect ELISA a nd an IgM-capture ELISA using DEN virus-infected cell culture pooled a ntigens. The results indicated that the trpE-DEN antigens and the cell culture antigens were equally sensitive for detecting IgM and IgG ant ibodies in convalescent sera from Peru and Indonesia representing viru s isolation-confirmed primary and secondary DEN infections, respective ly. Fourteen day postinfection IgG antibody-positive sera obtained fro m individuals infected with DEN-1 virus who had been vaccinated with o ther flaviviruses were more strongly reactive with the cell culture an tigen than with the recombinant antigen, but by day 21 postinfection, a strong antibody response to the trpE-DEN antigens was present. These results suggested that the early antibody response was directed predo minantly towards shared flavivirus group antigens that were not detect ed with the trpE-DEN antigens. Comparison of the trpE-DEN-1 recombinan t antigen with a DEN-1 virus-infected cell lysate antigen for the dete ction of IgG antibody in sera from a cohort of 55 individuals from Per u who seroconverted over a one-year period indicated greater specifici ty for the recombinant antigens. Also, sera from individuals with no k nown DEN infections that had been sequentially vaccinated with yellow fever and Japanese encephalitis reacted with the DEN virus cell cultur e antigen in the IgG ELISA, but did not react with the trpE-DEN pooled antigens. Similarly, YF IgM antibody positive samples that showed cro ss-reactivity with the DEN virus cell. culture antigens, did not react with the trpE-DEN pooled antigens. These results indicated that the t rpE-DEN pooled antigen provided a more specific diagnosis of dengue in fections than DEN virus-infected cell culture antigen and avoided the biohazards associated with handling live virus during the preparation of diagnostic reagents. The trpE-DEN pooled antigen should permit a be tter approach to distinguish between past DEN and other flavivirus inf ections in epidemiologic surveys, and also increase the specificity of serologic diagnosis of acute DEN infections.