Antibody-Dependent Respiratory Burst against Plasmodium falciparum Merozoites in Individuals Living in an Area with Declining Malaria Transmission

Abstract

Malaria transmission intensity affects the development of naturally acquired immunity to malaria. An absolute correlate measure of protection against malaria is lacking. However, antibody-mediated functions against <i>Plasmodium falciparum</i> correlate with protection against malaria. In children, antibody-mediated functions against <i>P. falciparum</i> decline with reduced exposure. It is unclear whether adults maintain antibody-mediated functions as malaria transmission declines. This study assessed antibody-dependent respiratory burst (ADRB) in individuals from an area with declining malaria transmission. In an age-matched analysis, we compare ADRB activity during high versus low malaria transmission periods. Age significantly predicted higher ADRB activity in the high (<i>p</i> < 0.001) and low (<i>p</i> < 0.001) malaria transmission periods. ADRB activity was higher during the high compared to the low malaria transmission period in older children and adults. Only older adults during the high malaria transmission period had their median ADRB activity above the ADRB cut-off. Ongoing <i>P. falciparum</i> infection influenced ADRB activity during the low (<i>p</i> = 0.01) but not the high (<i>p</i> = 0.29) malaria transmission period. These findings propose that naturally acquired immunity to <i>P. falciparum</i> is affected in children and adults as malaria transmission declines, implying that vaccines will be necessary to induce and maintain protection against malaria.