The characteristics of the immune response observed during the primary attack of Plasmodium vivax malaria were similar in sporozoite-induced and blood-induced cases. In both types of infections antibody production closely followed the appearance of parasites in the peripheral circulation, antibody levels abruptly rose to a maximum, stayed at high levels for about a month, and, after elimination of the parasites, gradually declined but persisted at low levels for extended periods of time. The close correlation between the appearance of the asexual forms of the malaria parasite and the first detection of antibody suggested that the asexual stages provided the antigenic stimulus. Evidence is presented which suggests that the gametocytes probably do not initiate the immune response. Results of studies in several blood-induced cases given many dead organisms suggested that killed parasites may be capable of provoking a mild antibody response. A pronounced booster effect, associated with the secondary antibody response, was observed in several volunteers who relapsed. Despite intermittent drug therapy given relatively early in the infection, all of the vivax cases under study exhibited an appreciable antibody response.
Laboratory of Germfree Animal Research.
Laboratory of Immunology—Present Address: Department of Medicine, University of North Carolina, Chapel Hill, North Carolina.
Laboratory of Clinical Investigations—Present Address: Peter Bent Brigham Hospital, Boston, Massachusetts.