Fetal-derived PF4+ tissue-resident macrophages recruit neutrophils as a key mechanism underlying DENV-2-induced intrauterine growth restriction in mice

Extensive clinical cases and epidemiological analyses have indicated that symptomatic dengue virus (DENV) infection may lead to adverse outcomes during pregnancy; however, the precise mechanisms remain elusive. In our previous work, we demonstrated that DENV-2 infection induces intrauterine growth restriction by triggering neutrophil-mediated destruction of the placental vascular system in mice. However, the specific mechanisms driving neutrophil infiltration into the placenta remain unclear, especially given that the placenta constitutes a unique immune-privileged niche dedicated to maintaining maternal-fetal tolerance. In this study, we generated a time-resolved single-cell atlas of placentas from interferon-alpha/beta receptor-deficient mice infected with DENV-2. Integrated analysis of single-cell transcriptomes and single-nucleotide polymorphism sequencing revealed that infection primarily activated fetal-origin tissue-resident PF4 + macrophages. Activated fetal macrophages mediate preferential recruitment and the subsequent aberrant accumulation of neutrophils in the labyrinth zone through the secretion of CXCL2, which binds to neutrophil CXCR2. Notably, the recruited neutrophils further exhibited an enhanced self-recruitment phenotype. Blocking CXCL2-CXCR2 signaling effectively inhibited neutrophil recruitment, restored placental microvascular density, and alleviated fetal intrauterine growth restriction. This study revealed that the activation of placental tissue-resident macrophages is responsible for the aberrant neutrophil infiltration in the placenta following DENV-2 infection. Mechanistically, macrophages initiate the recruitment of self-amplifying neutrophils, and the CXCL2-CXCR2 signaling pathway plays a crucial role in this process. These results provide important information for the clinical development of therapeutic strategies against DENV-2-induced adverse pregnancy outcomes.