Growth of Measles Virus in Epithelial and Lymphoid Tissues of Cynomolgus Monkeys

The pathogenesis of measles virus infection is not yet clearly understood, but clinical and pathological findings as well as experimental studies in monkeys indicate the invasion of measles virus through the respiratory epithelium and initial multiplication in the regional lymphoid tissues spreading into the reticuloendothelial system, and subsequent infection of the epithelial tissues including the trachea and skin.Thus both the lymphoreticular cells and epithelial cells are major sites for measles virus replication (4).In vitro growth of measles virus in the lymphoid cells has been used as the model of virus growth in these target cells in vivo (1, 2, 5).However, there is no report of a comparison of the in vivo growth of measles virus in epithelial and lymphoid cells.In the present study, characteristics of the growth of wild measles virus in the epithelial and lymphoid cells of cynomolgus monkeys (Macaca lascicularis) were compared by the immunofluorescence (IF) technique and electron microscopy.Pooled throat washings obtained from several patients with measles a few days after the onset of rash were used as the source of wild measles virus as described previously (9).Two cynomolgus monkeys free of measles-virus neutralizing antibody were subcutaneously inoculated with the throat washings.Seven days later, they were euthanasized by anesthetization with ketamine hydrochloride, and the brain, trachea, lungs, thymus, lymph nodes, spleen, kidneys, heart, and liver were removed.For the IF technique, the tissues were quickly frozen in n-hexane in a dry-ice-acetone bath.Thin sections made with a cryostat were fixed in acetone, and mixed with monoclonal antibodies against the Edmonston strain of measles virus including three clones against hemagglutinin (H) protein, one clone against nucleocapsid-associated phosphorylated (P) protein, one clone against nucleocapsid (NP) protein, two clones against fusion (F) proteins and two clones against membrane (M) protein (8), and then with goat anti-mouse IgG conjugated with fluorescein ≠Present