Protective and Complement-binding Bodies in the Serum of Human Yellow Fever Convalescents.

We have had the opportunity to make a serological study of 5 cases of yellow fever due to laboratory infections. The sera of 4 of these were examined for protective and complement-fixing bodies throughout convalescence so far as was practicable, while the serum of the other case was examined for the first property from the seventh week and for the second property from the eighth month after the onset of illness.

Protective antibodies: The technic of testing for the protective property was that usually employed, namely, the intraperitoneal inoculation of monkeys with serum, followed after 6 hours by the subcutaneous injection of fresh monkey blood containing virus. The table giving the results of these tests indicates that antibodies protecting monkeys against massive doses of virus appeared about the fifth day of illness in 4 cases. In the one instance in which serum was examined for the first time 7 weeks after illness, this protective property was present and repeatedly demonstrated thereafter.

Complement-binding bodies: The technic we employed in the complement-fixation tests was as described in a recent publication, 1 where the literature is briefly reviewed. It consisted essentially in the use as antigen of pooled infectious monkey serum preserved in a dry state, in the employment of a series of antigen dilutions against a constant dilution of serum, and in overnight fixation at 5°C. The usual controls were always included and in the experiments reported here were satisfactory.

A positive reaction appeared in one case in the eighth week after the onset of illness, and in another in the ninth week. The sera of 2 individuals gave positive tests at their first examination, 4 and 8 months after onset, while the reaction with the serum of one person has been consistently negative during the 8 months of observation after the acute attack.