A Latent Infection of Baby Hamster Kidney-21 Cells with Mumps Virus

Introduction We have recently reported the emergence of temperature-sensitive variants from a persistent infection of HeLa cells (HeLapi) with measles virus (1) and from a persistent infection of baby hamster kidney-21 cells (BHKpi) with mumps virus (2). The usefulness of in vitro persistent infections as correlates for in vivo disease processes is well recognized (3-5). The need for further study of mumps virus is indicated since the agent may be associated with clinical disorders such as diabetes (6), arthritis (7), primary endocardial fibroelastosis (8), Hodgkin's disease (9), and a number of other organ involvements (10-12). Moreover, the possibility exists that a persistent viral infection may be initiated by the use of attenuated strains of mumps virus in vaccine preparations. Our previous studies describing the characteristics of BHKpi revealed that at least two different populations of cell clones could be isolated (2). The first type consisted of normal BHK-21 cells lacking any detectable mumps virus components, as determined by hemadsorption, immunofluo-rescence, or released virus analysis. These uninfected cells were shown to be as susceptible to mumps virus as the original BHK-21 cells used in initiating the persistence. The second type consisted of BHK-21 cells demonstrating mumps virus antigens by hemadsorption (Had) and immunofluores-cence (ImF); however, no detectable released virus was demonstrable by assay in either primary chicken embryo or HeLa cell monolayers. This report describes a tissue culture system (BHKLI), derived from cell cloning of BHKpi, which is infected with a latent-in-ducible mumps virus. Methods. Cells. BHK-21 cells, clone 13, and HeLa cells were obtained from the American Type Culture Collection (Rock-ville, Maryland). Primary chicken embryo fibroblasts were prepared from 10- to 11-day-old embryonated eggs (Northwest Farms, Portland, Oregon). Cells were grown in Eagle's minimal essential medium (MEM) with Hank's salts, 10% heat-inactivated fetal calf serum (FCS) (Grand Island Biological Co., Grand Island, New York), 0.1% NaHCO3, 100 units/ml of penicillin G (potassium), and 100 μg/ml of streptomycin sulfate.