Figure 10.

Illustration of hematogenous CMV transmission in chorionic floating villi. Pathway 1: Uninfected syncytiotrophoblasts; IgG pinocytosed from maternal blood binds FcRn in endosomes and is recycled or transcytosed across the syncytium to the basal membrane. Pathway 2: Suppressed infection of IgG-virion complexes with high neutralizing activity that bind FcRn in endocytic vesicles at low pH, are transcytosed across the syncytiotrophoblast and released. IgG-virion envelope gB complexes stored in caveosomes (Cav) at neutral pH. Neutralized IgG-virion complexes transcytosed across syncytiotrophoblasts are captured by villus core macrophages (Mφ) and internalized by cytotrophoblasts. Pathway 3: Focal infection of cytotrophoblasts by IgG-virion complexes with low neutralizing activity. Infection could spread to stromal fibroblasts, blood vessels in the villus core, and leukocytes in the fetal bloodstream.16,42 Symbols for IgG, FcRn, virions (left margin). Red nuclei, infected cells.