g Although prior studies have characterized the neutralizing activities of monoclonal antibodies (MAbs) against dengue virus (DENV) serotypes 1, 2, and 3 (DENV-1, DENV-2, and DENV-3), few reports have assessed the activity of MAbs against DENV-4. Here, we evaluated the inhibitory activity of 81 new mouse anti-DENV-4 MAbs. We observed strain-and genotype-dependent differences in neutralization of DENV-4 by MAbs mapping to epitopes on domain II (DII) and DIII of the envelope (E) protein. Several anti-DENV-4 MAbs inefficiently inhibited at least one strain and/or genotype, suggesting that the exposure or sequence of neutralizing epitopes varies within isolates of this serotype. Remarkably, flavivirus cross-reactive MAbs, which bound to the highly conserved fusion loop in DII and inhibited infection of DENV-1, DENV-2, and DENV-3, more weakly neutralized five different DENV-4 strains encompassing the genetic diversity of the serotype after preincubation at 37°C. However, increasing the time of preincubation at 37°C or raising the temperature to 40°C enhanced the potency of DII fusion loop-specific MAbs and some DIII-specific MAbs against DENV-4 strains. Prophylaxis studies in two new DENV-4 mouse models showed that neutralization titers of MAbs after preincubation at 37°C correlated with activity in vivo. Our studies establish the complexity of MAb recognition against DENV-4 and suggest that differences in epitope exposure relative to other DENV serotypes affect antibody neutralization and protective activity.
Dengue virus (DENV) is a member of the Flaviviridae family of RNA viruses and is genetically related to other human pathogens of global concern, including yellow fever, West Nile (WNV), and Japanese encephalitis viruses. In nature, DENV disease occurs exclusively in humans after Aedes aegypti or Aedes albopictus mosquito inoculation, with clinical disease ranging from a debilitating febrile illness (dengue fever [DF]) to a life-threatening hemorrhagic and capillary leak syndrome (dengue hemorrhagic fever [DHF]/dengue shock syndrome [DSS]). No approved antiviral treatment is currently available, although candidate tetravalent vaccines are in advanced clinical trials (reviewed in references 1 and 2). Because of the increased geographic range of its mosquito vectors, urbanization, and international travel, DENV continues to spread worldwide and now causes an estimated 390 million infections and 500,000 cases of DHF/DSS per year, with 3.6 billion people at risk (3, 4). Given that the most advanced live-attenuated DENV vaccine candidate showed a poor 30% overall efficacy rate in a recently published phase 2b clinical trial (5), there is an urgent need for understanding the correlates of protection, especially those of neutralizing antibodies.DENV is an enveloped virus with a single-stranded, positivepolarity RNA genome. Based on experiments with DENV-1 and DENV-2 isolates, the mature DENV virion is ϳ500 Å in diameter with a highly organized outer protein shell, a 50-Å lipid membrane bilayer, and a nucleocapsid core ...