Abstract
BACKGROUND Naturally acquired immunity which is characterized by protection against overt clinical disease and high parasitemia is acquired with age and transmission intensity. The role of naturally acquired immunity on the efficacy of antimalarial drugs including artemisinin combination therapies (ACTs), the first-line treatments for uncomplicated Plasmodium falciparum has been demonstrated. This study investigated the role of naturally acquired immunity in the response to malaria ACT drug treatment in symptomatic patients living in a malaria high-transmission area of Western Kenya. METHODS This study used samples obtained from a therapeutic efficacy study conducted in western Kenya, an areas of high transmission which assessed ACTs. Sera samples from malaria immune (n = 105) and naïve participants (n = 6) were assessed for in vitro growth inhibitory activity against 3 D7 P. falciparum using a fluorescent-based Growth Inhibition Assay (GIA). Participants’ age and parasite clearance parameters were used in the analysis. RESULTS The key observations of the study are: (1) Sera with intact complement displayed higher GIA activity at lower serum dilutions; (2) there was significant relationship between GIA activity, parasite clearance rate, and slope half-life; (3) Age was a confounding factor when comparing the GIA activity with parasite clearance kinetics. CONCLUSION Taken together, this study demonstrates for the first time there is synergy of complement, pre-existing immunity, and drug treatment in younger patients with symptomatic malaria in a high-transmission area.
The Effect of Indoor Residual Spraying on Malaria and Anemia in a High-Transmission Area of Northern Uganda
