Distinct immune responses to HIV and CMV in Hofbauer cells across gestation highlight evolving placental immune dynamics.

Background: Hofbauer cells are fetal macrophages in the placental villous core that contribute to maternal-fetal tolerance and antiviral defense, but how their immune programs change across gestation in response to viral exposure remains poorly understood. Methods: Primary Hofbauer cells were isolated from early- to mid-gestation and term human placentas and exposed Results: Gestational stage strongly shaped both the transcriptional landscape and the magnitude of antiviral responses. At term, both HIV-1 and CMV induced a shared interferon-rich antiviral program, but CMV uniquely coupled this response to broad repression of mitochondrial and lipid metabolism, extracellular matrix and junctional pathways, and multiple placenta-enriched structural and immune genes. CMV exposure at term was also associated with remodeling of WNT signaling characterized by altered expression of Frizzled receptors and induction of the negative regulator Conclusion: Gestational stage establishes the immune-metabolic baseline of Hofbauer cells and strongly shapes their responses to viral exposure. At term, HIV and CMV converge on a shared interferon-driven antiviral program, but CMV uniquely couples this response to coordinated disruption of metabolic, structural, and signaling pathways in Hofbauer cells. These findings suggest that CMV drives a metabolically and structurally constrained antiviral state, providing a mechanistic framework linking CMV exposure to placental vulnerability and enhanced HIV susceptibility at the maternal-fetal interface.