Autoantibodies to Extracellular Erythrocyte Band 3 Epitopes Are Associated With Anemia in Plasmodium vivax Infection.

Plasmodium vivax-associated anemia is a multifactorial clinical outcome, in which the destruction of uninfected red blood cells (uRBCs) plays a major role in disease development and severity. Here, we identified autoantibody targets within the extracellular loops of Band 3 (B3), a major erythrocyte transmembrane protein. In silico epitope prediction identified six of the seven potentially immunogenic extracellular domains of B3. Patients with P. vivax infection who were anemic (n = 79) and non-anemic (n = 95), and 40 healthy donors from a non-endemic area were included as negative controls. In addition, 15 anemic and 15 non-anemic infected individuals were also analyzed immediately before treatment (D0) and on Days 7, 14, and 28 after antimalarial therapy. Synthetic peptides corresponding to the six B3 domains were robustly recognized by autoantibodies from P. vivax -infected patients. Anemic individuals exhibited prominent autoantibody responses, particularly against loops 4 and 6. IgG3 was the predominant subclass targeting these loops and remained detectable up to 28 days post-treatment, suggesting a possible role in the persistence of anemia even after parasite clearance. In contrast, IgG1 was the principal subclass recognizing the peptides corresponding to loops 1, 2, and 3, indicating a significant response to senescent domains during P. vivax infection. Analysis of IgG subclass against full-length B3 confirmed the presence of both IgG1 and IgG3 responses. The pro-inflammatory properties of these IgG subclasses support the hypothesis that anti-B3 autoantibodies contribute to the immunopathogenesis of P. vivax -related anemia. Collectively, these findings identify potential targets for future mechanistic investigations and therapeutic intervention strategies.