Immunity to one of the four dengue virus (DV) serotypes can increase disease severity in humans upon subsequent infection with another DV serotype. Serotype cross-reactive antibodies facilitate DV infection of myeloid cells in vitro by promoting virus entry via Fcγ receptors (FcγR), a process known as antibody-dependent enhancement (ADE). However, despite decades of investigation, no in vivo model for antibody enhancement of dengue disease severity has been described. Analogous to human infants who receive anti-DV antibodies by transplacental transfer and develop severe dengue disease during primary infection, we show here that passive administration of anti-DV antibodies is sufficient to enhance DV infection and disease in mice using both mouse-adapted and clinical DV isolates. Antibody-enhanced lethal disease featured many of the hallmarks of severe dengue disease in humans, including thrombocytopenia, vascular leakage, elevated serum cytokine levels, and increased systemic viral burden in serum and tissue phagocytes. Passive transfer of a high dose of serotype-specific antibodies eliminated viremia, but lower doses of these antibodies or cross-reactive polyclonal or monoclonal antibodies all enhanced disease in vivo even when antibody levels were neutralizing in vitro. In contrast, a genetically engineered antibody variant (E60-N297Q) that cannot bind FcγR exhibited prophylactic and therapeutic efficacy against ADE-induced lethal challenge. These observations provide insight into the pathogenesis of antibody-enhanced dengue disease and identify a novel strategy for the design of therapeutic antibodies against dengue.

Dengue virus (DENV) causes dengue fever and dengue haemorrhagic fever/dengue shock syndrome, both considered major public-health problems worldwide. We generated a lethal DENV-2 strain (D220) by 10 additional cycles of subcutaneous inoculation of mice with supernatant from mosquito cells infected with the previously characterized strain D2S10, followed by harvesting of serum. D220 induces mortality at ten-fold lower doses than D2S10 in mice lacking only the alpha/beta interferon (IFN-a/b) receptor in C57BL/6 or 129 backgrounds under both non-enhanced and antibody-enhanced conditions. Sequence analysis of the complete viral genome revealed five amino acid changes between D220 and D2S10, of which two (K122I in envelope and V115A in NS4B) appear to account for the observed phenotypic differences between the viruses. By causing mortality at lower doses in C57BL/6 mice lacking only the IFNa/b receptor, D220 constitutes an improved tool for study of DENV-induced pathogenesis, as well as for testing potential vaccines and antiviral drugs against DENV.The four serotypes of dengue virus (DENV-1-4) are mosquitoborne and cause dengue fever (DF) and dengue haemorrhagic fever/dengue shock syndrome (DHF/DSS). Found in tropical and subtropical regions of the world, DENV causes an estimated 50-100 million infections annually and places over 3 billion people at risk of infection (WHO, 2009). Most primary DENV infections with any serotype are asymptomatic or lead to the self-limited febrile illness DF; however, secondary infection with a different DENV serotype leads to increased risk of developing severe dengue disease (Halstead, 2007). This increase in severity upon secondary infection is thought to be mediated in part via antibody-dependent enhancement (ADE), whereby interaction between antibodies generated during a prior infection and the current infecting serotype can lead to increased uptake of virus via Fc receptors expressed on susceptible myeloid cells (Halstead, 2003).Establishing a small-animal model is an important step in understanding the mechanisms underlying dengue pathogenesis and immunity. The first mouse models used high doses of neurovirulent DENV strains delivered intracranially into immunocompetent mice; this caused neurotropic disease and paralysis in infected mice, which is typically not observed in human dengue (Raut et al., 1996;Schlesinger, 1977). One of the second-generation models used a neurotropic mouseadapted DENV2 strain in mice of the 129/Sv mouse background deficient in alpha/beta interferon (IFN-a/b) and IFN-c receptors (AG129 mice) (Johnson & Roehrig, 1999;Zompi & Harris, 2012). In more recent work, a peripherally adapted DENV-2 virus, designated D2S10, was generated by alternately passaging the Taiwanese DENV-2 isolate PL046 between Aedes albopictus C6/36 cells and AG129 mouse serum. The D2S10 virus was lethal in AG129 mice at 10 7 p.f.u. and induced a vascular leak phenotype mediated in part by tumour necrosis factor alpha (TNF-a) (Shresta et al., 2006), which is similar to observations in s...

No abstract