On Infectious Mononucleosis

Abstract

In the spring of 1941, during the occurrence of an epidemic of infectious mononucleosis, we attempted to isolate a transmissible agent from sterile Berkefeld filtrates of nasal washings and whole blood by inoculation into the chorio-allantoic membrane of the chick embryo. Material was obtained from patients who gave a characteristic history, blood picture, and whose heterophile antibody titers ranged from complete agglutination of 160 to a high of 2560. We also attempted passage from patients whose clinical history and leucocyte picture were typical and who later gave heterophile agglutinations in the range mentioned. The nasal washings and blood from some patients were frozen for 12 hours before they were used. Two additional cases made their appearance this fall. In all, a total of 8 attempts was made to transmit the agent from 8 cases; positive results were obtained from 4. The sterile filtrate, when inoculated onto the membrane, showed small pearl-gray reactions with a spreading cloudiness about them. This reaction occurred after the third to the fifth day of inoculation and continued to grow until the membranes were harvested for study. Of 66 membranes which were inoculated with sterile nasal washings, 19 showed positive reactions. Of 30 membranes inoculated with whole blood, 13 showed positive reactions. Cultures from all infective membranes were bacteriologically sterile. Nasal washings and blood from 2 normal individuals were negative. Microscopically, the positive membrane showed an ectodermal proliferation and heavy monocytic cell infiltration. Although special stain was applied, (Mallory phloxine-methylene blue) no inclusion bodies were found. We are able to continue the reaction through 4 to 14 passages obtaining positive results with about 50% of the membranes. The agent finally died out, showing a dramatic drop of positive takes in the last 2 generations of each passage.