Lymphocyte proliferative response and subset profiles during extended periods of chloroquine or primaquine prophylaxis

Immune suppression and disturbances of normal leukocyte populations are side effects attributed to many antimalarial drugs and were concerns during a recent year-long placebo-controlled trial that compared daily primaquine (0.5 mg of base per kg of body weight per day) with weekly chloroquine (300 mg of base one time per week) for malaria prophylaxis. The study took place in Irian Jaya, Indonesia, from July 1994 to August 1995 and enrolled 129 Javanese men with normal glucose-6-phosphate dehydrogenase function. Tests for lymphocyte function and subset composition were conducted blindly on a cross-section of subjects during weeks 10 (n = 42) and 48 (n = 72) of supervised prophylaxis. Lymphocyte function, measured as the proliferative response of peripheral blood mononuclear cells to a panel of mitogens (pokeweed mitogen, phytohemagglutinin, and concanavalin A) and antigens (purified protein derivative of Mycobacterium tuberculosis and Clostridium tetani toxoid) and expressed as a stimulation index, allowed for statistical comparison between groups and sampling times. The lymphocyte subset composition for each group and time point was based on flow cytometry profiling, and the results were expressed as the mean percentages of CD3 (total T cells), CD19 (total B cells), CD4+ (T-helper and inducer cells), and CD8+ (T suppressor and cytotoxic cells), CD3/CD16+ CD56 (natural killer cells), CD3/anti-HLA-DR (activated T cells) cells and the CD4+/CD8+ ratios. Lymphocyte stimulation indices were statistically comparable among the placebo, primaquine, and chloroquine groups at both time points, although the primaquine group was distinguished by having repeatedly greater proportions of subjects with high ( > 3.0) stimulation indices. The lymphocyte subset profiles of these groups at both time points were also similar and undistorted relative to those of healthy reference populations matched for age, sex, and ethnicity. The results provide quantitative support for the safety of daily primaquine prophylaxis.