Salivary glands and human congenital cytomegalovirus infection: What happens in early fetal life?

Salivary glands are a site of human cytomegalovirus (CMV) replication, latency, and persistence. Prolonged secretion of virus in saliva for months following a primary infection contribute to horizontal transmission. In order to better understand the early effects of CMV on salivary glands and the mechanisms of viral persistent replication, submandibular glands of six CMV congenitally infected fetuses at 21 weeks gestation were studied. Three fetuses at the same gestational age from CMV-seronegative women were compared as negative controls. Tissue viral load and the type of inflammatory infiltrate were evaluated. Moreover, development and branching of salivary glands, the number of myoepithelial cells, cellular proliferation, and expression of secretory proteins of the saliva (Gross Cystic Disease Fluid Protein-15 and lysozyme) were studied. A low viral load and rare CMV-positive cells associated with T CD8 cytotoxic lymphocytes were observed. Branching was impaired with a decrease in terminal acinar structures, the number of myoepithelial cells, and cellular proliferation were reduced. In addition, a compromised secretion of defense proteins involved in the oral humoral immunity was observed. These findings suggest that CMV may affect salivary glands, impairing structure development and secretion of defense proteins, probably responsible for the prolonged viral shedding in saliva.