V. Evaluation of Cross-Immunity against Type 1 Dengue Fever in Human Subjects Convalescent from Subclinical Natural Japanese Encephalitis Virus Infection and Vaccinated with 17D Strain Yellow Fever Vaccine
A test antigen has been prepared from the microfilariae of Wuchereria bancrofti for the immunological diagnosis of infections with this parasite.
The method of preparation of the antigen was as follows: citrated blood containing numerous microfilariae was hemolyzed by mixing with 10 volumes per unit of a 2 per cent solution of saponin made up in 0.85 per cent saline. The hemolyzed blood was centrifuged at about 2000 R.P.M. for 10 minutes. The supernatant fluid was examined at several levels for the presence of microfilariae and found to be negative. The sediment was treated again with fresh saponin solution, followed by several washings in saline and a final wash in distilled water after which it was dried in vacuum.
Large numbers of living microfilariae were concentrated by the method outlined above and found in the sediment. It was noted also that they were accompanied by leukocytes which could not be removed.
Assistant professor of parasitology School of Tropical Medicine, Columbia University, San Juan, Puerto Rico.
Lieut. Colonel, Med. Corps, A.U.S. Assistant clinical professor of medicine New York Post-Graduate Medical School, Columbia University, New York, N. Y. On leave of absence.