Effect of sialodacryoadenitis virus exposure on acinar epithelial cells from the rat lacrimal gland

Abstract

Sialodacryoadenitis virus (SDAV), a RNA coronavirus, in-duces degenerative, necrotic and atrophic alterations in acinar epithelial cells of the rat lacrimal gland. To begin to explore the underlying mechanism(s) of this viral effect, we sought in the present study to: (i) determine whether SDAV invades and replicates in lacrimal gland acinar cells in vitro; and (2) assess whether short-term SDAV challenge interferes with the viability or function of acinar cells in vitro. For comparison we also evaluated the rela-tive infectivity of SDAV in acinar epithelial cells from lacrimal, submandib-ular and parotid glands, given that salivary tissues are known to be highly susceptible to SDAV infection in vivo. Acinar epithelial cells from lacrimal, submandibular or parotid glands were isolated from male rats, exposed briefly to SDAV or control cell antigen and then cultured for four, eight or twelve days. At experimental termination, SDAV titers in both media and sonicated cell extracts were evaluated by plaque assay titration on mouse L2 cell monolayers. To evaluate functional aspects of lacrimal gland acinar cells, SDAV-infected cells were incubated in the presence or absence of dihydrotestosterone and culture media were analyzed by RIA to measure the extent of the androgen-induced increase in secretory component (SC) pro-duction. Our results showed that: (i) SDAV invades and replicates in lacri-mal gland acinar cells. Viral challenge resulted in a significant, time-depen-dent increase in SDAV titers, that were primarily cell-associated and greatly exceeded amounts contained in the original inoculum; (2) SDAV infection did not compromise lacrimal acinar cell viability or prevent the cellular SC response to androgens. Viral presence, though, did often attenuate the mag-nitude of this hormone action; and (3) SDAV infects salivary acinar cells, but the kinetics and magnitude of viral replication in lacrimal, submandibu-lar and parotid cells showed considerable variations. These findings demon-strate that SDAV invades and replicates in acinar epithelial cells from lacri-mal and salivary glands. The resulting release of infectious progeny may play a role in the SDAV-induced pathology of exocrine tissues in vivo.