# IFN‑γ Production in Memory CD4 + T Cells in Response to MSP119 Antigen and Its Correlation with Anemia and Thrombocytopenia in Pediatric Vivax Malaria

## TL;DR

The study shows that memory T cells producing IFN-γ in response to a specific malaria antigen are linked to better recovery from anemia and low platelet counts in children with vivax malaria.

## Contribution

The study identifies sustained IFN-γ production in memory CD4+ T cells as a marker of immunity and improved clinical outcomes in pediatric vivax malaria.

## Key findings

- Children with sustained IFN-γ production in CD4+ memory T cells had lower parasite density and faster recovery of hemoglobin and platelet levels.
- The PvMSP119 antigen is proposed as a promising marker for sustained immunity in vivax malaria.
- The IFN-γ response in memory T cells correlates with reduced severity of anemia and thrombocytopenia.

## Abstract

Plasmodium
vivax (P. vivax) can
lead to severe hematological complications,
including anemia and thrombocytopenia, which may require hospitalization.
This prospective observational study investigated the adaptive immune
response in pediatric P. vivax malaria,
focusing on sustained IFN-γ production in CD4+ and
CD8+ memory T cells as markers of immune protection. Conducted
at the Dr. Heitor Vieira Dourado Tropical Medicine Foundation (FMT-HVD)
in the Western Brazilian Amazon, peripheral blood mononuclear cells
(PBMCs) were collected from 25 children aged 1–16 years at
diagnosis (D0, acute phase) and 90 days post-treatment (D90, convalescent
phase). PBMCs were stimulated ex vivo with the conserved P. vivax antigen, the 19 kDa fragment of the C-terminal
region of merozoite surface protein-1 (PvMSP119), and intracellular production of IFN-γ was quantified
in memory T cells (CD3+CD4+CD45RO+ and CD3+CD8+CD45RO+ T cells) by
flow cytometry. Individuals whose cells specifically produced IFN-γ
against PvMSP119 on both D0 and D90 were
classified as responders, while those who responded in only one phase
or in neither were classified as nonresponders. Responders, whose
CD3+CD4+CD45RO+ T cells exhibited
sustained IFN-γ response against PvMSP119 demonstrated lower parasite density as well as improved
normalization of hemoglobin levels and recovery of platelet counts.
These results confirm the role of this response as acquisition of
immunity. PvMSP119 antigen emerges as
a promising marker of sustained immunity, though larger studies are
required to evaluate its long-term impact on recovery and outcomes.
These findings underscore the critical role of IFN-γ-producing
memory T cells in controlling parasitemia and mitigating anemia and
thrombocytopenia in pediatric P. vivax malaria.