Analysis of the humoral response induced by Dengue and Zika virus infection using recombinant proteins from the envelope of these viruses.

The Flaviviridae are a family of RNA viruses transmitted mainly by arthropods that may infect humans. Members of this family are responsible for a great number of infections, and present considerable morbidity and mortality all around the globe. In Brazil, we have the circulation of the dengue virus (DENV), which has circulated in the country for decades and is responsible for many recurrent epidemics, and also other Flaviviruses, such as the Yellow Fever virus (YFV), and more recently, the zika virus (ZIKV). The four serotypes of DENV (DENV1-4) are 65% to 70% similar in their aminoacid sequence, which may have important consequences for pathogenesis, with the amplification of secondary infections caused by a heterologous serotype through immunocomplexes of the virus and sub-neutralizing antibodies, or in protection, with the induction of cross-reactive neutralizing antibodies. Therefore, it is essential to use recombinant proteins that represent well the native virus proteins in studies analyzing the humoral immune response induced in DENV infections. Among the alternatives of protein expression systems, the insect cell system is effective because it generates proteins more similar to the native ones when compared to the bacterial expression system. For this reason, in our work we generated recombinant envelope (E) proteins of DENV and also its domains: domain I and II (EDI/II) and domain III (EDIII) in Drosophila S2 cells. With these, we evaluated the cross-reactivity of sera from previously DENV infected patients against the DENV2 and DENV3 E protein. Furthermore, with these sera, we also measured the humoral immune response against each domain (EDI/II and EDIII) of the DENV2 E protein, and evaluated the seras neutralization capacity against DENV2. Lastly, we compared the DENV2 E recombinant proteins produced in S2 cells or in bacteria. The proteins produced in the eukaryotic system showed a conformation closer to the native one, and better specificity and sensitivity than the ones produced in the prokaryotic system, and therefore theyre better alternatives for the study of the humoral immune response generated against DENV. (AU)