Evaluation of the precision of the Plasmodium knowlesi growth inhibition assay for Plasmodium vivax Duffy-binding protein-based malaria vaccine development

Jonas E Mertens; Cassandra A Rigby; Martino Bardelli; Doris Quinkert; Mimi M Hou; Ababacar Diouf; Sarah E Silk; Chetan E Chitnis; Angela M Minassian; Robert W Moon; Carole A Long; Simon J Draper; Kazutoyo Miura

doi:10.1016/j.vaccine.2024.04.073

Evaluation of the precision of the Plasmodium knowlesi growth inhibition assay for Plasmodium vivax Duffy-binding protein-based malaria vaccine development

Vaccine. 2024 May 3:S0264-410X(24)00514-0. doi: 10.1016/j.vaccine.2024.04.073. Online ahead of print.

Authors

Affiliations

¹ Department of Biochemistry, University of Oxford, Dorothy Crowfoot Hodgkin Building, Oxford OX1 3QU, United Kingdom; Kavli Institute for Nanoscience Discovery, University of Oxford, Dorothy Crowfoot Hodgkin Building, Oxford OX1 3QU, United Kingdom; Institute for Infection Research and Vaccine Development (IIRVD), University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany.
² Department of Biochemistry, University of Oxford, Dorothy Crowfoot Hodgkin Building, Oxford OX1 3QU, United Kingdom; Kavli Institute for Nanoscience Discovery, University of Oxford, Dorothy Crowfoot Hodgkin Building, Oxford OX1 3QU, United Kingdom.
³ Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville 20852, MD, United States.
⁴ Unité de Biologie de Plasmodium et Vaccins, Institut Pasteur, Université Paris Cité, 25-28 Rue du Dr Roux, 75015 Paris, France.
⁵ Department of Biochemistry, University of Oxford, Dorothy Crowfoot Hodgkin Building, Oxford OX1 3QU, United Kingdom; Kavli Institute for Nanoscience Discovery, University of Oxford, Dorothy Crowfoot Hodgkin Building, Oxford OX1 3QU, United Kingdom; NIHR Oxford Biomedical Research Centre, Oxford, United Kingdom.
⁶ Department of Infection Biology, London School of Hygiene and Tropical Medicine, London WC1E 7HT, United Kingdom.
⁷ Department of Biochemistry, University of Oxford, Dorothy Crowfoot Hodgkin Building, Oxford OX1 3QU, United Kingdom; Kavli Institute for Nanoscience Discovery, University of Oxford, Dorothy Crowfoot Hodgkin Building, Oxford OX1 3QU, United Kingdom; NIHR Oxford Biomedical Research Centre, Oxford, United Kingdom. Electronic address: simon.draper@bioch.ox.ac.uk.
⁸ Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville 20852, MD, United States. Electronic address: kmiura@niaid.nih.gov.

PMID: 38704253
DOI: 10.1016/j.vaccine.2024.04.073

Abstract

Recent data indicate increasing disease burden and importance of Plasmodium vivax (Pv) malaria. A robust assay will be essential for blood-stage Pv vaccine development. Results of the in vitro growth inhibition assay (GIA) with transgenic P. knowlesi (Pk) parasites expressing the Pv Duffy-binding protein region II (PvDBPII) correlate with in vivo protection in the first PvDBPII controlled human malaria infection (CHMI) trials, making the PkGIA an ideal selection tool once the precision of the assay is defined. To determine the precision in percentage of inhibition in GIA (%GIA) and in GIA₅₀ (antibody concentration that gave 50 %GIA), ten GIAs with transgenic Pk parasites were conducted with four different anti-PvDBPII human monoclonal antibodies (mAbs) at concentrations of 0.016 to 2 mg/mL, and three GIAs with eighty anti-PvDBPII human polyclonal antibodies (pAbs) at 10 mg/mL. A significant assay-to-assay variation was observed, and the analysis revealed a standard deviation (SD) of 13.1 in the mAb and 5.94 in the pAb dataset for %GIA, with a LogGIA₅₀ SD of 0.299 (for mAbs). Moreover, the ninety-five percent confidence interval (95 %CI) for %GIA or GIA₅₀ in repeat assays was calculated in this investigation. The error range determined in this study will help researchers to compare PkGIA results from different assays and studies appropriately, thus supporting the development of future blood-stage malaria vaccine candidates, specifically second-generation PvDBPII-based formulations.

Keywords: Blood-stage malaria antigen; Growth inhibition assay; Plasmodium vivax; Precision; PvDBPII; Vaccine.