Zika virus (
ZIKV) has recently been associated with
birth defects and
pregnancy loss after maternal
infection. Because
dengue virus (DENV) and
ZIKV co-circulate,
understanding the
role of
antibody-dependent enhancement in the context of
pregnancy is critical. Here, we showed that the presence of DENV-specific
antibodies in
ZIKV-infected pregnant
mice significantly increased placental damage,
fetal growth restriction, and
fetal resorption. This was associated with enhanced viral replication in the
placenta that coincided with an increased frequency of infected
trophoblasts.
ZIKV-infected
human placental
tissues also showed increased replication in the presence of DENV
antibodies, which was reversed by FcγR
blocking antibodies. Furthermore,
ZIKV-mediated fetal
pathogenesis was enhanced in
mice in the presence of a DENV-reactive monoclonal antibody, but not in the presence of the LALA variant, indicating a dependence on FcγR engagement. Our data suggest a possible mechanism for the recent increase in severe
pregnancy outcomes after
ZIKV infection in DENV-endemic areas.