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 in vitro for 24 h to HIV-1 or cytomegalovirus (CMV), together with mock controls. Transcriptional responses were profiled by bulk RNA sequencing using differential expression, pathway enrichment, and co-expression network analyses, integrated with placenta-enriched gene annotations from the Human Protein Atlas. Secreted cytokines were quantified using a multiplex bead assay.

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 RNF43, consistent with receptor-level feedback control of the pathway. In contrast, HIV-1 at term preserved proliferative, antigen-presentation, and T-cell co-stimulation signatures. In early- to mid-gestation Hofbauer cells, viral exposure did not yield significant DEGs but showed coordinated pathway-level changes, with HIV-1 favoring interferon-associated signaling and CMV preferentially altering metabolic and remodeling pathways.

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.