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

## TL;DR

This study shows that as malaria transmission declines, antibody-mediated immunity against malaria also decreases in both children and adults, suggesting vaccines may be needed to maintain protection.

## Contribution

The study demonstrates how antibody-dependent respiratory burst activity changes in individuals as malaria transmission declines.

## Key findings

- ADRB activity was higher during high malaria transmission periods in older children and adults.
- Ongoing P. falciparum infection influenced ADRB activity during low transmission but not high transmission periods.
- Naturally acquired immunity declines with reduced malaria exposure, suggesting a need for vaccines.

## 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 Plasmodium falciparum correlate with protection against malaria. In children, antibody-mediated functions against P. falciparum 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 (p < 0.001) and low (p < 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 P. falciparum infection influenced ADRB activity during the low (p = 0.01) but not the high (p = 0.29) malaria transmission period. These findings propose that naturally acquired immunity to P. falciparum is affected in children and adults as malaria transmission declines, implying that vaccines will be necessary to induce and maintain protection against malaria.