Cytomegaloviruses as Common Adventitious Contaminants in Primary African Green Monkey Kidney Cell Cultures

Abstract

Twenty-seven of fifty-two lots of primary African green monkey (AGM) kidney cell cultures were found to contain cytomegalovirus (CMV). The cell cultures, all derived from apparently healthy animals, required long incubation periods before CMV could be detected. Less than half the contaminated cultures showed cytopathic effects (CPE) before 4 weeks. About one-fifth of the contaminated cultures failed to show CPE during a 40-day observation period; CMV was initially recognized in these cultures by fluorescence microscopy. Fluorescence and electron microscopy of CMV-infected cells revealed highly distinctive nuclear inclusions. All virus strains tested showed typical focal CPE on monolayers of WI-38 cells after 5 days. Nearly all AGM sera tested contained complement-fixing antibody against several simian CMV strains. Substantial levels of neutralizing antibody against one CMV strain were present in AGM sera tested. Isolation and serological data indicate that CMV is widely distributed as a latent infection among apparently healthy African green monkeys. This wide distribution in well-conditioned monkeys might be considered when the significance of herpes-like viruses in primate cells is interpreted. Simian CMV-human cell interactions are of interest because of the well-known association of herpesviruses with oncogenic processes and because simian CMV strains replicate slowly in human cells.