Abstract:
Dengue viruses (DENVs) are health threats to over two billion of people around the World. Infection by DENV could result in vascular leakage, hypovolemic shock, multi-organ dysfunction or, ultimately, death. Monocytes are one of the natural targets of the DENVs. Monocytes are recognized as one of the key players on symptomatic dengue by secreting cytokines that involve in inflammation and vascular leakage. To further investigate role of monocytes on development of symptomatic dengue, responses of DENV-experiencing monocytes and DENV-naïve monocytes to DENV-2 infection were compared. In this study, monocytes were obtained from three groups of donors that were DENV-immune donors, DENV-non-immune donors and DENV-naïve individuals. Classification of donors was based on whether they expressed detectable level of anti-Flavivirus antibodies (anti-DENVs antibody or anti-JEV antibody) detected by PRNT and hemagglutination inhibition test. These three sets of monocytes were either directly infected with DENV-2 or infected with DENV-enhancing antibody complexes. The replication efficiency of DENV-2 and production of cytokines known to involve in severe dengue (IL-6, IL-10, IL-1β and IFN-γ) were compared. We found the monocytes from these three groups of donors supported DENV replication at the same efficiency when comparing between the same route of infection. As expected, infection via DENV-enhancing antibody complexes increased replication efficiency compared to direct infection. This enhancing activity was independent to the levels of CD64 and CD32 expression on monocytes. For cytokine production, we found that DENV-naïve monocytes produced the lowest levels of IL-6, IL-1β and IFN-γ while DENV-immune monocytes secreted the highest levels of these cytokines in response to direct DENV infection. Moreover, infection via enhancing antibody significantly upregulated production of IL-10 from monocytes from all three groups while increasing production of IL-6 from DENV-immune and DENV-non-immune monocytes but not DENV-naïve monocytes. We further found that monocytes from these three groups did not differentiated into M1 macrophages in response to DENV infection.