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Kho S, Barber BE, Johar E, Andries B, Poespoprodjo JR, Kenangalem E, Piera KA, Ehmann A, Price RN, William T, Woodberry T, Foote S, Minigo G, Yeo TW, Grigg MJ, Anstey NM, McMorran BJ. Platelets kill circulating parasites of all major Plasmodium species in human malaria. Blood 2018; 132:1332-1344. [PMID: 30026183 PMCID: PMC6161646 DOI: 10.1182/blood-2018-05-849307] [Citation(s) in RCA: 70] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2018] [Accepted: 06/27/2018] [Indexed: 01/12/2023] Open
Abstract
Platelets are understood to assist host innate immune responses against infection, although direct evidence of this function in any human disease, including malaria, is unknown. Here we characterized platelet-erythrocyte interactions by microscopy and flow cytometry in patients with malaria naturally infected with Plasmodium falciparum, Plasmodium vivax, Plasmodium malariae, or Plasmodium knowlesi Blood samples from 376 participants were collected from malaria-endemic areas of Papua, Indonesia, and Sabah, Malaysia. Platelets were observed binding directly with and killing intraerythrocytic parasites of each of the Plasmodium species studied, particularly mature stages, and was greatest in P vivax patients. Platelets preferentially bound to the infected more than to the uninfected erythrocytes in the bloodstream. Analysis of intraerythrocytic parasites indicated the frequent occurrence of platelet-associated parasite killing, characterized by the intraerythrocytic accumulation of platelet factor-4 and terminal deoxynucleotidyl transferase deoxyuridine triphosphate nick-end labeling of parasite nuclei (PF4+TUNEL+ parasites). These PF4+TUNEL+ parasites were not associated with measures of systemic platelet activation. Importantly, patient platelet counts, infected erythrocyte-platelet complexes, and platelet-associated parasite killing correlated inversely with patient parasite loads. These relationships, taken together with the frequency of platelet-associated parasite killing observed among the different patients and Plasmodium species, suggest that platelets may control the growth of between 5% and 60% of circulating parasites. Platelet-erythrocyte complexes made up a major proportion of the total platelet pool in patients with malaria and may therefore contribute considerably to malarial thrombocytopenia. Parasite killing was demonstrated to be platelet factor-4-mediated in P knowlesi culture. Collectively, our results indicate that platelets directly contribute to innate control of Plasmodium infection in human malaria.
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Affiliation(s)
- Steven Kho
- Global and Tropical Health Division, Menzies School of Health Research and Charles Darwin University, Darwin, NT, Australia
| | - Bridget E Barber
- Global and Tropical Health Division, Menzies School of Health Research and Charles Darwin University, Darwin, NT, Australia
- Infectious Diseases Society Sabah-Menzies School of Health Research Clinical Research Unit, Kota Kinabalu, Sabah, Malaysia
| | - Edison Johar
- Department of Immunology and Infectious Disease, The John Curtin School of Medical Research, Australian National University, Canberra, ACT, Australia
| | - Benediktus Andries
- Timika Malaria Research Programme, Papuan Health and Community Development Foundation, Timika, Papua, Indonesia
| | - Jeanne R Poespoprodjo
- Timika Malaria Research Programme, Papuan Health and Community Development Foundation, Timika, Papua, Indonesia
- Rumah Sakit Umum Daerah Kabupaten Mimika, Timika, Papua, Indonesia
- Department of Paediatrics, University of Gadjah Mada, Yogyakarta, Indonesia
| | - Enny Kenangalem
- Timika Malaria Research Programme, Papuan Health and Community Development Foundation, Timika, Papua, Indonesia
- Rumah Sakit Umum Daerah Kabupaten Mimika, Timika, Papua, Indonesia
| | - Kim A Piera
- Global and Tropical Health Division, Menzies School of Health Research and Charles Darwin University, Darwin, NT, Australia
| | - Anna Ehmann
- Department of Immunology and Infectious Disease, The John Curtin School of Medical Research, Australian National University, Canberra, ACT, Australia
| | - Ric N Price
- Global and Tropical Health Division, Menzies School of Health Research and Charles Darwin University, Darwin, NT, Australia
- Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, United Kingdom
| | - Timothy William
- Infectious Diseases Society Sabah-Menzies School of Health Research Clinical Research Unit, Kota Kinabalu, Sabah, Malaysia
- Jesselton Medical Centre, Kota Kinabalu, Sabah, Malaysia; and
- Clinical Research Centre, Queen Elizabeth Hospital, Kota Kinabalu, Sabah, Ministry of Health, Malaysia
| | - Tonia Woodberry
- Global and Tropical Health Division, Menzies School of Health Research and Charles Darwin University, Darwin, NT, Australia
| | - Simon Foote
- Department of Immunology and Infectious Disease, The John Curtin School of Medical Research, Australian National University, Canberra, ACT, Australia
| | - Gabriela Minigo
- Global and Tropical Health Division, Menzies School of Health Research and Charles Darwin University, Darwin, NT, Australia
| | - Tsin W Yeo
- Global and Tropical Health Division, Menzies School of Health Research and Charles Darwin University, Darwin, NT, Australia
- Infectious Diseases Society Sabah-Menzies School of Health Research Clinical Research Unit, Kota Kinabalu, Sabah, Malaysia
| | - Matthew J Grigg
- Global and Tropical Health Division, Menzies School of Health Research and Charles Darwin University, Darwin, NT, Australia
- Infectious Diseases Society Sabah-Menzies School of Health Research Clinical Research Unit, Kota Kinabalu, Sabah, Malaysia
| | - Nicholas M Anstey
- Global and Tropical Health Division, Menzies School of Health Research and Charles Darwin University, Darwin, NT, Australia
- Infectious Diseases Society Sabah-Menzies School of Health Research Clinical Research Unit, Kota Kinabalu, Sabah, Malaysia
| | - Brendan J McMorran
- Department of Immunology and Infectious Disease, The John Curtin School of Medical Research, Australian National University, Canberra, ACT, Australia
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