Resumo

Dengue virus (DENV) belongs to the Flaviviridae family and comprises four serotypes, named DENV1-4. Dengue infection is associated to a spectrum of clinical manifestations, ranging from mild symptoms to the severe forms of dengue, which seems to be associated to an exacerbated inflammatory response and antibody-dependent enhancement. Antibody-mediated response is essential to virus neutralization and infection control, but is also attributed to exacerbated infection and severe dengue. It has been recently demonstrated that DENV-infected patients present an increased activation of B cells, and we have previously demonstrated that culture of primary human B lymphocytes with different DENV serotypes induces increased immunoglobulin response. However, the role of direct virus infection and the receptors involved in this activation were not addressed yet. CD81 is part of the B cell co-receptor complex and plays an important role in Hepatitis C virus (HCV) infection, another member of the family. The aim of this study was to investigate whether human B cells are productively infected by DENV and to evaluate the influence of CD81 in activation, adsorption and subsequent DENV replication. Purified human B lymphocytes were cultured with CD81 neutralizing antibody and infected with DENV-2 at a multiplicity of infection (MOI) of 1. The activation of B cells was analyzed by measuring IgM secretion by ELISA and qRT-PCR was used by viral quantification in the adsorption and replication assays. We observed that DENV induced and increased secretion of IgM after 10 to 15 days of culture, which was abolished in cells treated with anti-CD81 antibody. qRT-PCR of the B cells cultured with DENV demonstrated that the virus is internalized and secreted, but the amount of virus detected in B cells of all donors after 24, 48 and 72 h post-infection was not altered, indicating that DENV was unable to productively replicate in these cells. In addition, anti-CD81 treatment did not influence on virus adsorption and internalization. These results suggest DENV interaction with CD81 in the surface of B cell is essential to induce cell activation, but it is not associated to virus adsorption and internalization. The interaction of CD81 and viral proteins may be associated to polyclonal activation of B cells and their knowledge might provide a better understanding of the pathophysiology of dengue.