28th Annual Conference of the European Society for Clinical Virology

Introduction/Aim: Congenital cytomegalovirus (cCMV) infection is the most common congenital viral infection and a leading cause of neurodevelopmental impairment, yet clinical outcomes vary widely even among fetuses exposed to the same maternal infection. Twin pregnancies represent a unique model to investigate fetal-intrinsic and placental factors contributing to this heterogeneity. We hypothesized that host genetic background and cell-specific environments influence viral replication and disease expression in cCMV infection. Material: Three monochorionic diamniotic twin pairs with suspected or confirmed cCMV infection were enrolled. Methods: Human cytomegalovirus (HCMV) clinical isolates were recovered from urine samples and phenotypically characterized in human foreskin fibroblasts (HFF), retinal pigment epithelial (ARPE-19) cells, and ex vivo placental explants. In parallel, 1H NMR–based metabolomic profiling of neonatal urine samples and virus genetic analyses were performed. Results were integrated with clinical findings. Results: HCMV clinical isolates exhibited overall growth properties with limited phenotypic and genotypic variability. However, metabolomic analyses highlighted distinct molecular signatures between the twin pairs. Betaine, creatinine, and gluconate were identified as metabolites discriminating against individuals based on infection status, recovery phase, and nutritional or pharmacological management. Conclusions: This integrative multi-omics study in twins provides evidence that host background and cellular context contribute to variability in viral replication and biological outcomes in cCMV infection. These findings support a role for fetal-intrinsic factors in disease heterogeneity and may inform future strategies for early risk stratification and personalized management.