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 of protection against malaria is lacking. However, anti-body-mediated functions against P. falciparum correlate with protection against malaria. In children, antibody-mediated functions against P. falciparum generally decline with a reduction in exposure; however, it is unclear whether adults maintain antibody-mediated functions in the context of re-duced exposure. 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 both the high and low malaria transmission periods. Within all age categories, ADRB activity was higher during the high compared to the low malaria transmission period, with only the adults during the high malaria transmission period having their mean ADRB activity above the ADRB cut-off. Interestingly, ongoing P. falciparum infection influenced ADRB activity during the low but not the high malaria transmission period. These findings propose that naturally acquired immunity to P. falciparum is affected in children and adults as malaria transmission declines, im-plying that vaccines will be necessary to induce and maintain protection against malaria.