Correlation Between Malaria-Specific Antibody Profiles and Responses to Artemisinin Combination Therapy for Treatment of Uncomplicated Malaria in Western Kenya

Background. The impact of preexisting immunity on the efficacy of artemisinin combination therapy must be examined to monitor resistance, and for implementation of new treatment strategies. Methods. Serum samples obtained from a clinical trial in Western Kenya randomized to receive artemether-lumefantrine (AL) or artesunate-mefloquine (ASMQ) were screened for total immunoglobulin G against preerythrocytic and erythrocytic antigens. The association and correlation between different variables, and impact of preexisting immunity on parasite slope half-life (t(1/2)) was determined. Results. There was no significant difference in t(1/2), but the number of individuals with lag phase was significantly higher in the AL than in the ASMQ arm (29 vs 13, respectively; P <.01). Circumsporozoite protein-specific antibodies correlate positively with t(1/2) (AL, P =.03; ASMQ, P =.09), but negatively with clearance rate in both study arms (AL, P =.16; ASMQ, P =.02). The t(1/2) correlated negatively with age in ASMQ group. When stratified based on t(1/2), the antibody titers against circumsporozoite protein and merozoite surface protein 1 were significantly higher in participants who cleared parasites rapidly in the AL group (P =.01 and P =.02, respectively). Conclusion. Data presented here define immunoprofiles associated with distinct responses to 2 different antimalarial drugs, revealing impact of preexisting immunity on the efficacy of artemisinin combination therapy regimens in a malaria-holoendemic area.