Detection of Higher Levels of Dengue Viremia Using FcγR-expressing BHK-21 Cells Than FcγR-negative Cells in Secondary Infection but Not in Primary Infection

It has been reported that levels of viremia reflect the severity of illness in dengue virus infection. We assessed the levels of viremia in patients with primary and secondary infections, using 2 cell lines: Fc gamma R-expressing BHK cells and Fc gamma R-negative cells. In primary infection, virus titers were at similar levels between Fc gamma R-expressing and Fc gamma R-negative cells. In secondary infection, however, virus titers were similar to 10 times higher in Fc gamma R-expressing cells on days 1-6 when compared with Fc gamma R-negative cells, indicating discrepancy in viremia titers between Fc gamma R-expressing and Fc gamma R-negative cells. The results suggest that dengue virus-antibody complexes with infectious capacity exist in patients with secondary infection, and these immune complexes can be detected by using Fc gamma R-expressing cells. As it has been reported that principal target cells of dengue virus infection are Fc gamma R-positive, monocyte/macrophage lineage cells, virus titers determined using Fc gamma R-expressing cells may better reflect the actual viremic conditions in vivo.