Plasmodium knowlesi tryptophan-rich antigen 40.1 binds human erythrocyte spectrin alpha
11 affiliations
- 1Department of Tropical Medicine, School of Medicine, Kangwon National University, Chuncheon, Republic of Korea
- 2Department of Epidemiology and Tropical Diseases, Faculty of Public Health, Universitas Diponegoro, Semarang, Indonesia
- 3Department of Parasitic Diseases and Vector Control, National Institute for Medical Research, Dar es Salaam, Tanzania
- 4Department of Pathogen Biology and Immunology, School of Medicine, Yangzhou University, Yangzhou, China
- 5Department of Parasitology and Tropical Medicine, Inha University School of Medicine, Incheon, Republic of Korea
- 6Department of Obstetrics and Gynecology, Kangwon National University Hospital, Chuncheon, Republic of Korea
- 7Department of Pharmacology, School of Medicine, Kangwon National University, Chuncheon, Republic of Korea
- 8Department of Physiology, School of Medicine, Kangwon National University, Chuncheon, Republic of Korea
- 9Department of Parasitology, Faculty of Medicine, Universiti Malaya, Kuala Lumpur, Malaysia
- 10Department of Infection Biology, Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom
- 11Institute of Medical Sciences, Kangwon National University, Chuncheon, Republic of Korea
Abstract
Plasmodium infection induces extensive remodeling of host erythrocytes through parasite-exported proteins that interact with host cell components. Among these, tryptophan-rich antigens (TRAgs) are conserved across Plasmodium species and have been proposed as vaccine candidates, but their molecular functions remain largely unexplored. In this study, we characterized Plasmodium knowlesi tryptophan-rich antigen 40.1 (PkTRAg40.1) to investigate its localization, biochemical properties, host interactions, and immunogenicity. Recombinant PkTRAg40.1 showed no detectable binding to intact human erythrocytes in flow cytometry-based binding assays. Biochemical characterization demonstrated that native PkTRAg40.1 was predominantly associated with detergent-resistant insoluble fractions and was detected as multiple higher-molecular-weight forms. Protease protection assays further showed that native PkTRAg40.1 was accessible to protease under the experimental conditions tested. Consistent with these observations, immunofluorescence assays revealed that PkTRAg40.1 colocalized with skeleton-binding protein 1 (PkSBP1), supporting its localization to Sinton and Mulligan’s clefts (SMCs), parasite-derived membranous structures. Pull-down assays and MALDI-TOF/MS identified spectrin alpha as a host binding partner, and biolayer interferometry confirmed its specific interaction with the spectrin alpha α12–16 fragment (KD = 4.71 ± 0.62 μM). Serological analysis of P. knowlesi patient samples revealed that PkTRAg40.1 is immunogenic, exhibiting 50% sensitivity and 92.9% specificity, and also displayed cross-reactivity with sera from Plasmodium vivax-infected patients. Collectively, these findings identify PkTRAg40.1 as a TRAg associated with parasite-derived membranous structures that interacts with the host erythrocyte cytoskeleton, thereby expanding current understanding of the molecular functions of Plasmodium TRAgs. Author summary: Malaria parasites extensively remodel infected red blood cells by exporting proteins that interact with host cell components. Tryptophan-rich antigens (TRAgs) are conserved across Plasmodium species and are considered important for parasite biology, but their molecular functions remain unclear. Although previous studies have suggested that some TRAgs may associate with parasite-induced membrane structures and host cell structural components, the biological significance of these observations has yet to be established. We characterized PkTRAg40.1 from the zoonotic malaria parasite P. knowlesi to investigate its localization, host interactions, and immunogenicity. We found that recombinant PkTRAg40.1 showed no measurable binding to intact human erythrocytes in flow cytometry-based binding assays. Instead, PkTRAg40.1 localized to parasite-induced membranous structures within infected erythrocytes. Biochemical analyses identified spectrin alpha, a major component of the erythrocyte membrane skeleton, as a host binding partner. Patient sera further showed that PkTRAg40.1 is immunogenic and is recognized by antibodies from P. knowlesi-infected patients. To our knowledge, this is the first study to identify an interaction between a P. knowlesi TRAg and a host erythrocyte structural protein. These findings provide new molecular insight into the interaction of PkTRAg40.1 with host membrane and cytoskeletal components and provide a framework for future studies investigating the biological functions of TRAg proteins.
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BibTeX
@article{lee2026plasmodium,
title = {{Plasmodium knowlesi tryptophan-rich antigen 40.1 binds human erythrocyte spectrin alpha}},
author = {Wang-Jong Lee and Fadhila Fitriana and Jadidan Hada Syahada and Johnsy Mary Louis and Hyun-Young Sim and Ernest Mazigo and Hojong Jun and Fauzi Muh and Feng Lu and Seok Ho Cha and Se Jin Lee and Sunghun Na and Wanjoo Chun and Won Sun Park and Yee Ling Lau and Robert W. Moon and Eun-Taek Han and Jin-Hee Han},
journal = {PLOS Neglected Tropical Diseases},
year = {2026},
month = sep,
doi = {10.1371/journal.pntd.0014700},
url = {https://journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0014700},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Plasmodium knowlesi tryptophan-rich antigen 40.1 binds human erythrocyte spectrin alpha
AU - Wang-Jong Lee
AU - Fadhila Fitriana
AU - Jadidan Hada Syahada
AU - Johnsy Mary Louis
AU - Hyun-Young Sim
AU - Ernest Mazigo
AU - Hojong Jun
AU - Fauzi Muh
AU - Feng Lu
AU - Seok Ho Cha
AU - Se Jin Lee
AU - Sunghun Na
AU - Wanjoo Chun
AU - Won Sun Park
AU - Yee Ling Lau
AU - Robert W. Moon
AU - Eun-Taek Han
AU - Jin-Hee Han
PY - 2026
DA - 2026/09/17
JO - PLOS Neglected Tropical Diseases
DO - 10.1371/journal.pntd.0014700
UR - https://journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0014700
AB - Plasmodium infection induces extensive remodeling of host erythrocytes through parasite-exported proteins that interact with host cell components. Among these, tryptophan-rich antigens (TRAgs) are conserved across Plasmodium species and have been proposed as vaccine candidates, but their molecular functions remain largely unexplored. In this study, we characterized Plasmodium knowlesi tryptophan-rich antigen 40.1 (PkTRAg40.1) to investigate its localization, biochemical properties, host interactions, and immunogenicity. Recombinant PkTRAg40.1 showed no detectable binding to intact human erythrocytes in flow cytometry-based binding assays. Biochemical characterization demonstrated that native PkTRAg40.1 was predominantly associated with detergent-resistant insoluble fractions and was detected as multiple higher-molecular-weight forms. Protease protection assays further showed that native PkTRAg40.1 was accessible to protease under the experimental conditions tested. Consistent with these observations, immunofluorescence assays revealed that PkTRAg40.1 colocalized with skeleton-binding protein 1 (PkSBP1), supporting its localization to Sinton and Mulligan’s clefts (SMCs), parasite-derived membranous structures. Pull-down assays and MALDI-TOF/MS identified spectrin alpha as a host binding partner, and biolayer interferometry confirmed its specific interaction with the spectrin alpha α12–16 fragment (KD = 4.71 ± 0.62 μM). Serological analysis of P. knowlesi patient samples revealed that PkTRAg40.1 is immunogenic, exhibiting 50% sensitivity and 92.9% specificity, and also displayed cross-reactivity with sera from Plasmodium vivax-infected patients. Collectively, these findings identify PkTRAg40.1 as a TRAg associated with parasite-derived membranous structures that interacts with the host erythrocyte cytoskeleton, thereby expanding current understanding of the molecular functions of Plasmodium TRAgs. Author summary: Malaria parasites extensively remodel infected red blood cells by exporting proteins that interact with host cell components. Tryptophan-rich antigens (TRAgs) are conserved across Plasmodium species and are considered important for parasite biology, but their molecular functions remain unclear. Although previous studies have suggested that some TRAgs may associate with parasite-induced membrane structures and host cell structural components, the biological significance of these observations has yet to be established. We characterized PkTRAg40.1 from the zoonotic malaria parasite P. knowlesi to investigate its localization, host interactions, and immunogenicity. We found that recombinant PkTRAg40.1 showed no measurable binding to intact human erythrocytes in flow cytometry-based binding assays. Instead, PkTRAg40.1 localized to parasite-induced membranous structures within infected erythrocytes. Biochemical analyses identified spectrin alpha, a major component of the erythrocyte membrane skeleton, as a host binding partner. Patient sera further showed that PkTRAg40.1 is immunogenic and is recognized by antibodies from P. knowlesi-infected patients. To our knowledge, this is the first study to identify an interaction between a P. knowlesi TRAg and a host erythrocyte structural protein. These findings provide new molecular insight into the interaction of PkTRAg40.1 with host membrane and cytoskeletal components and provide a framework for future studies investigating the biological functions of TRAg proteins.
SN - 1935-2735
ER -