Development of a Primary Human Cell Model for the Study of Human Cytomegalovirus Replication and Spread within Salivary Epithelium.

Various aspects of human cytomegalovirus (HCMV) pathogenesis, including its ability to replicate in specific cells and tissues and the mechanism(s) of horizontal transmission, are not well understood, predominantly because of the strict species specificity exhibited by HCMV. Murine CMV (MCMV), which contains numerous gene segments highly similar to those of HCMV, has been useful for modeling some aspects of CMV pathogenesis; however, it remains essential to build relevant human cell-based systems to investigate how the HCMV counterparts function. The salivary gland epithelium is a site of persistence for both human and murine cytomegaloviruses, and salivary secretions appear to play an important role in horizontal transmission. Therefore, it is important to understand how HCMV is replicating within the glandular epithelial cells so that it might be possible to therapeutically prevent transmission. In the present study, we describe the development of a salivary epithelial model derived from primary human "salispheres." Initial infection of these primary salivary cells with HCMV occurs in a manner similar to that reported for established epithelial lines, in that gH/gL/UL128/UL130/UL131A (pentamer)-positive strains can infect and replicate, while laboratory-adapted pentamer-null strains do not. However, while HCMV enters the lytic phase and produces virus in salivary epithelial cells, it fails to exhibit robust spread throughout the culture and persists in a low percentage of salivary cells. The present study demonstrates the utility of these primary tissue-derived cells for studying HCMV replication in salivary epithelial cells in vitro IMPORTANCE Human cytomegalovirus (HCMV) infects the majority of the world's population, and although it typically establishes a quiescent infection with little to no disease in most individuals, the virus is responsible for a variety of devastating sequelae in immunocompromised adults and in developing fetuses. Therefore, identifying the viral properties essential for replication, spread, and horizontal transmission is an important area of medical science. Our studies use novel human salivary gland-derived cellular models to investigate the molecular details by which HCMV replicates in salivary epithelial cells and provide insight into the mechanisms by which the virus persists in the salivary epithelium, where it gains access to fluids centrally important for horizontal transmission.