Effect of Seasonal Malaria Chemoprevention on Immune Markers of Exhaustion and Regulation

Abstract

Background: Seasonal malaria chemoprevention (SMC) is a novel strategy to reduce malaria infections in children. Infection with Plasmodium falciparum results in immune dysfunction characterized by elevated expression of markers associated with exhaustion, such as PD1 and LAG3, and regulatory CD4+FOXP3+ T cells.

Methods: In the current study, the impact of seasonal malaria chemoprevention on malaria-induced immune dysfunction, as measured by markers associated with exhaustion and regulatory T cells, was explored by flow cytometry.

Results: Children that received seasonal malaria chemoprevention had fewer malaria episodes and showed significantly lower fold changes in CD4+PD1+ and CD4+PD1+LAG3+ compared to those that did not receive SMC. Seasonal malaria chemoprevention had no observable effect on fold changes in CD8 T cells expressing PD1 or CD160. However, children receiving SMC showed greater increases in CD4+FOXP3+ T regulatory cells compared to children not receiving SMC.

Conclusions: These results provide important insights into the dynamics of malaria-induced changes in the CD4 T-cell compartment of the immune system and suggest that the reduction of infections due to seasonal malaria chemoprevention may also prevent immune dysfunction.

Clinical trials registration: NCT02504918.

Keywords: T-cell exhaustion; T-cell regulation; immune dysfunction; seasonal malaria chemoprevention.

Figure 1.

Gating strategy used to identify CD4⁺PD1⁺, CD4⁺PD1⁺LAG3⁺, CD4⁺FOXP3⁺, CD8⁺PD1⁺, and CD8⁺CD160⁺ populations within the CD3⁺ gate. Abbreviations: FSC, forward scatter; FOXP3, forkhead box P3; LAG3, lymphocyte activation gene-3; PD1, programmed cell death protein-1; SSC, side scatter.

Figure 2.

Proportion of malaria infections (A) and clinical malaria episodes (B) during the follow-up months in the children enrolled in the SMC+ and SMC− groups. Differences between the groups were evaluated using the X² test. Abbreviation: SMC, seasonal malaria chemoprevention.

Figure 3.

Comparison of (A) time to first positive blood smear and (B) time to first clinical malaria infection in children in the SMC+)and control group, SMC−. Data were analyzed using the log-rank test. Abbreviation: SMC, seasonal malaria chemoprevention.

Figure 4.

Mean fold change from baseline of (A) CD4⁺PD1⁺ and (B) CD4⁺PD1⁺LAG3⁺ during the study period in the SMC+ and SMC− groups. Data are represented as mean fold change and error bars denote the 95% confidence interval. Generalized estimating equations were used to analyze differences between the groups. Abbreviations: LAG3, lymphocyte activation gene-3; PD1, programmed cell death protein-1; SMC, seasonal malaria chemoprevention.

Figure 5.

Mean fold change from baseline of CD4⁺FOXP3⁺ during the study period in the SMC+ and SMC− groups. Error bars represent the 95% confidence intervals. Generalized estimating equations were used to analyze differences between the groups. Abbreviations: FOXP3, forkhead box P3; SMC, seasonal malaria chemoprevention