Avaliação da resposta imune de células T em infecção humana pelo vírus dengue com ênfase em células T reguladoras

Abstract

Dengue is a viral acute disease caused by four different serotypes (DENV1, DENV2, DENV3 or DENV4) and very present on tropical and subtropical countries. The disease can be classified as dengue without warning sings (DWS-), dengue with warning signs (DWS+) and severe dengue (SD), which can be fatal. It is speculated that exacerbated inflammatory process underlies SD, however little is known about the mechanisms that regulates inflammatory process in dengue infection. Regulatory T cells (Tregs) are major regulators of inflammatory responses through secretion of anti-inflammatory cytokines, like IL-10, or by direct inhibition of effector cells through receptors like CD200, LAP, GITR, PD-1, among others. The study of regulatory mechanisms mediated by Tregs can provide insight about how the host controls acute infection inflammation preventing complications. In order to evaluate immunological response profile, PBMCs were isolated from blood samples from healthy and dengue-infected subjects and kept frozen at -196°C until use. After thawing, cells were cultured with antigenic stimuli and subjected to multi-parametric flow cytometry. We observed that DWS- individuals showed significant increase in the production inflammatory cytokines like, IFNγ and TNFα, from dengue-specific T cells as early as 7 days post-fever (PF). In addition, T cells from DWS- patients displayed dengue-specific production of IL-10 at 30 days PF, in contrast to DWS+ subjects. Despite no differences in frequency of Tregs (CD4+CD25highCD127lowFoxP3+) observed between dengue classifications, Tregs cells from DWS- patients expressed higher frequencies of CD200 and GITR when compared to DWS+ group. Importantly, a population of dengue-specific Tregs producing high levels of IL-10 was detected in DWS- subjects, but not in DWS+ individuals. Other regulatory molecules, like PD-1 and LAP, were not different between groups. DWS- individuals displayed earlier dengue-specific T cell production of IFNγ and TNF than DWS+ patients. In addition, dengue-specific pro-inflammatory response was associated with regulatory mechanisms (IL-10, CD200 and GITR), suggesting that balanced immune response is important for a favorable clinical evolution of dengue.