The response of monkeys infected with Plasmodium knowlesi was followed using the indirect fluorescent-antibody technique.
All animals showed an increase in FA response as a result of the malarial infection. Individual monkeys reacted quite differently to infection; some required repeated periodic drug therapy, whereas in others chronic infection readily occurred without extended treatment. In some monkeys the antibody response reached very high levels (1:1280), whereas in others the peak response was only 1:80. Thus it would be difficult, if not impossible, to determine the length or intensity of previous infection with P. knowlesi by the level of FA response obtained.
Through the use of a filter-paper technique to collect daily serum samples, it was possible to determine that the initial increase in FA response was on the 7th to 9th day of patency.
National Institutes of Health, Malaria Project, U. S. Penitentiary, Atlanta, Georgia.