DENV type 4 Envelope protein (50 kDa)

Zika virus (ZIKV), an emerging mosquito-borne flavivirus, has quickly spread in many regions around the world where dengue virus (DENV) is endemic. This represents a major health concern, given the high homology between these two viruses, which can result in cross-reactivity. The aim of this study was to determine the cross-reacting antibody response of the IgM and IgG classes against the recombinant envelope protein of ZIKV (rE-ZIKV) in sera from patients with acute-phase infection of different clinical forms of dengue, i.e., dengue fever (DF) and dengue hemorrhagic fever (DHF) (before the arrival of ZIKV in Mexico 2010), as well as acute-phase sera of ZIKV patients, together with the implications in neutralization and antibody-dependent enhancement. Differences in IgM responses were observed in a number of DF and DHF patients whose sera cross-reacted with the rE-ZIK antigen, with 42% recognition between acute-phase DHF and ZIKV but 27% recognition between DF and ZIKV. Regarding IgG antibodies, 71.5% from the DF group showed cross-reactivity to rE-ZIKV in contrast with 50% and only 25% of DHF and ZIKV serum samples, respectively, which specifically recognized the homologous antigen. The DHF group showed more enhancement of ZIKV infection of FCR gamma-expressing cells compared to the DF group. Furthermore, the DHF group also showed a higher cross-neutralizing ability than that of DF. This is the first report where DF and DHF serum samples were evaluated for cross-reactivity against Zika protein and ZIKV. Furthermore, DENV serum samples cross-protect against ZIKV through neutralizing antibodies but at the same time mediate antibody-dependent enhancement in the sequential ZIKV infection.

Dengue virus causes about 100 million cases of dengue disease per year in the world. Laboratory diagnosis is done mainly by serological techniques, which in many cases use crude virus extracts that may cause cross-reactions to other flaviviruses. These undesirable cross-reactions can be reduced or eliminated by using recombinant proteins based on restricted epitopes. Aiming to decrease flaviviral cross-reactions and non-specific interactions in dengue serological assays, a plant expression system was chosen for recombinant antigen production as a reliable and inexpensive dengue diagnostic tool. In the present report, the lettuce plastid transformation system was applied to achieve efficient and stable tetra-epitope peptide antigen production, and its reactivity was evaluated. For this purpose, one putative epitope at positions 34 to 57 of E protein within the junction site of domains I and II of dengue virus (DENV) 1 to 4 serotypes linked by glycine linkers was expressed in lettuce chloroplasts. The potential immunoreactivity for the four DENV serotypes was evaluated using sera from patients of positive and negative dengue cases. Results indicated an overall sensitivity of 71.7 % and specificity of 100 %. No cross-reactions with the sera of yellow fever-positive or healthy individuals vaccinated against yellow fever were observed. This novel approach may provide an alternative system for the large-scale production of dengue recombinant antigens useful for serodiagnosis.