The placental transport of HCMV - implications for congenital infection by neonatal Fc receptor

Human Cytomegalovirus (HCMV) is a pervasive pathogen with significant implications for neonatal health, particularly due to its potential for mother-to-fetus (mother-to-embryo) transmission during pregnancy. Despite ongoing research efforts, effective pharmaceutical interventions or vaccines to prevent this mode of transmission remain elusive. Congenitally infected infants often suffer varying degrees of disabilities, with deafness being the most common consequence, posing a substantial risk to newborn health. This dissertation explores the mechanisms underlying the placental transport of HCMV, focusing on the implications of neonatal Fc receptor (FcRn) mediated congenital infection. The study aimed to develop a stable in vitro model of the maternal-fetal interface, emphasizing the roles of viral Fcγ receptors (vFcγRs) in mediating HCMV's linkage to FcRn, and to elucidate the active transport processes and mechanisms of HCMV across the fetal syncytiotrophoblast (STB). In pursuit of these objectives, we evaluated various existing maternal-fetal cell-based in vitro models, ultimately establishing a Transwell® (TW) assay that forms a stable single cell layer, mimicking trophoblast cells' unique characteristics. Through lentivirus transduction technology, the monocytic layer was engineered to express the HA-FCGRT gene, enhancing its interaction with IgG. This assay facilitated quantitative analysis of IgG transcytosis across human STB, highlighting FcRn's pivotal role as the primary transcytosis receptor in our experimental setup. We found that BeWo cells, among various cell types transduced with the FCGRT gene, were most suitable for the TW assay. Optimal antibody concentrations were determined through titration, refining the TW assay's applicability to a broader range of cells, viruses, and antibodies, and laying groundwork for subsequent experiments. Our findings revealed that HCMV, aided by IgG, could efficiently traverse the TW assay's single-cell layer, while viruses lacking the two vFcγRs demonstrated significantly hindered passage. Furthermore, in viral infectivity assays, we observed that Cytotect®, an anti-HCMV Hyperimmune Globulin (HIG), could neutralize HCMV's virulence, impeding its ability to reinfect other epidermal cells. Conversely, antagonizing both vFcγRs substantially reduced HCMV's transcytosis capability, underscoring the importance of vFcγRs' interaction with IgG in manipulating FcRn to facilitate viral spread. The study's findings pave the way for future therapeutic strategies targeting HCMV's hijacking mechanism of FcRn, potentially leading to the development of novel, effective pharmaceuticals or vaccines to prevent HCMV's mother-to-fetus transmission. This research not only contributes to a deeper understanding of HCMV's transplacental transport mechanisms but also opens avenues for mitigating the risks associated with congenital HCMV infection.