In vitro invasion inhibition assay using antibodies against Plasmodium knowlesi Duffy binding protein alpha and apical membrane antigen protein 1 in human erythrocyte-adapted P. knowlesi A1-H.1 strain

Fauzi Muh, Seong-Kyun Lee, Mohammad Rafiul Hoque, Jin-Hee Han, Ji-Hoon Park, Egy Rahman Firdaus, Robert W. Moon, Yee Ling Lau, Eun-Taek Han*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

14 Citations (Scopus)
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Abstract

Background: The rapid process of malaria erythrocyte invasion involves ligand-receptor interactions. Inducing antibodies against specific ligands or receptors that abrogate the invasion process is a key challenge for blood stage vaccine development. However, few candidates were reported and remain to be validated for the discovery of new vaccine candidates in Plasmodium knowlesi.

Methods: In order to investigate the efficacy of pre-clinical vaccine candidates in P. knowlesi-infected human cases, this study describes an in vitro invasion inhibition assay, using a P. knowlesi strain adapted to in vitro growth in human erythrocytes, PkA1-H. 1. Recombinant proteins of P. knowlesi Duffy binding protein alpha (PkDBPα) and apical membrane antigen 1 (PkAMA1) were produced in Escherichia coli system and rabbit antibodies were generated from immune animals.

Results: PkDBPα and PkAMA1 recombinant proteins were expressed as insoluble and produced as a functional refolded form for this study. Antibodies against PkDBPα and PkAMA1 specifically recognized recombinant proteins and native parasite proteins in schizont-stage parasites on the merozoite organelles. Single and combination of anti-PkDBPα and anti-PkAMA1 antibodies elicited strong growth inhibitory effects on the parasite in concentrationdependent manner. Meanwhile, IgG prevalence of PkDBPα and PkAMA1 were observed in 13.0 and 46.7% in human clinical patients, respectively.

Conclusion: These data provide support for the validation of in vitro growth inhibition assay using antibodies of DBPα and AMA1 in human-adapted P. knowlesi parasite PkA1-H. 1 strain.

Original languageEnglish
Article number272
Number of pages11
JournalMalaria Journal
Volume17
DOIs
Publication statusPublished - 27 Jul 2018

Keywords

  • Plasmodium knowlesi
  • Zoonotic malaria
  • PkDBP alpha
  • PkAMA1
  • Invasion
  • Inhibition

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