First Experimental In Vivo Model of Enhanced Dengue Disease Severity through Maternally Acquired Heterotypic Dengue Antibodies

Dengue (DEN) represents the most serious arthropod-borne viral disease. DEN clinical manifestations range from mild febrile illness to life-threatening hemorrhage and vascular leakage. Early epidemiological observations reported that infants born to DEN-immune mothers were at greater risk to develop the severe forms of the disease upon infection with any serotype of dengue virus (DENV). From these observations emerged the hypothesis of antibody-dependent enhancement (ADE) of disease severity, whereby maternally acquired anti-DENV antibodies cross-react but fail to neutralize DENV particles, resulting in higher viremia that correlates with increased disease severity. Although in vitro and in vivo experimental set ups have indirectly supported the ADE hypothesis, direct experimental evidence has been missing. Furthermore, a recent epidemiological study has challenged the influence of maternal antibodies in disease outcome. Here we have developed a mouse model of ADE where DENV2 infection of young mice born to DENV1-immune mothers led to earlier death which correlated with higher viremia and increased vascular leakage compared to DENV2-infected mice born to dengue naive mothers. In this ADE model we demonstrated the role of TNF- in DEN-induced vascular leakage. Furthermore, upon infection with an attenuated DENV2 mutant strain, mice born to DENV1-immune mothers developed lethal disease accompanied by vascular leakage whereas infected mice born to dengue naive mothers did no display any clinical manifestation. In vitro ELISA and ADE assays confirmed the cross-reactive and enhancing properties towards DENV2 of the serum from mice born to DENV1-immune mothers. Lastly, age-dependent susceptibility to disease enhancement was observed in mice born to DENV1-immune mothers, thus reproducing epidemiological observations. Overall, this work provides direct in vivo demonstration of the role of maternally acquired heterotypic dengue antibodies in the enhancement of dengue disease severity and offers a unique opportunity to further decipher the mechanisms involved. Author Summary Dengue (DEN) is an arthropod-transmitted viral disease which affects approximately 390 million individuals in the tropical and subtropical world annually. DEN clinical manifestations range from mild febrile illness (dengue fever) to life-threatening dengue hemorrhagic/dengue shock syndrome (DHF/DSS). Epidemiological observations indicate that infants born to dengue immune mothers are at greater risk to develop the severe form of the disease (DHF/DSS) upon infection with any serotype of dengue virus (DENV). It was proposed that the presence of maternally acquired DENV specific antibodies cross react but fail to neutralize DENV particles, resulting in higher viremia that correlates with increased disease severity. Direct experimental evidence supporting this antibody-dependent enhancement (ADE) hypothesis has been missing. Furthermore, a recent epidemiological report has challenged the influence of maternally acquired antibodies in disease outcome. Here, we have developed a mouse model of ADE where DENV2-infected mice born to DENV1 immune mothers displayed enhanced disease severity compared to DENV2-infected mice born to dengue naive mothers. This is a long-overdue direct experimental evidence of the role of maternally acquired antibodies in dengue disease outcome. It provides a unique opportunity to dissect the mechanisms involved in this phenomenon.