Dengue virus isolation relying on antibody-dependent enhancement mechanism using FcγR-expressing BHK cells and a monoclonal antibody with infection-enhancing capacity

BackgroundVirus isolation is the most reliable evidence of dengue virus (DENV) infection. However, conventional virus isolation methods generally posses lower sensitivity and are time consuming as compared to other diagnostic methods such as detection of viral genome by RT-PCR, and determination of NS1 antigen and anti-DENV antibody by ELISA.ObjectivesA virus isolation method relying on the antibody-dependent enhancement mechanism was established and the assay's efficacy in DENV isolation was confirmed.Study designFcγR-expressing BHK cells were used for DENV isolation from patient serum samples in the presence of a flavivirus-group reactive monoclonal antibody, mAb4G2, which possesses DENV infection-enhancement activity. DENV genome copy numbers in the culture supernatant fluids of FcγR-expressing BHK cells were assessed and compared to those of parent BHK cells and C6/36 mosquito cells, a cell line commonly used for DENV isolation.ResultsThe virus titer levels were higher in the culture supernatant fluid of FcγR-expressing BHK cells in the presence of enhancing antibody in comparison with other cell lines using laboratory-established strains and some clinical samples. DENV was isolated from 7 of 16 serum samples by using FcγR-expressing BHK cells in the presence of mAb4G2, but not by using cell lines commonly employed in conventional isolation assays, the FcγR-negative BHK cells and C6/36 cell lines.ConclusionsThe results demonstrate that FcγR-expressing BHK cell line in the presence of antibodies, which possess antibody dependent enhancement (ADE) activity, is a useful tool for DENV isolation.