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Invasion of Plasmodium knowlesi merozoite into human erythrocytes involves molecular interaction between the parasite’s Duffy binding protein (PkDBPαII) and the Duffy antigen receptor for chemokines on the erythrocytes. This study investigates the binding activity of human erythrocyte with PkDBPαII of P. knowlesi isolates from high and low parasitemic patients in an erythrocyte binding assay. The binding activity was determined by counting the number and measuring the size of rosettes formed in the assay. The protein PkDBPαII of P. knowlesi isolated from low parasitemia cases produced significantly higher number of rosettes with human erythrocytes than high parasitemia case isolates (65.5 ± 12.9 and 17.2 ± 5.5, respectively). Interestingly, PkDBPαII of isolates from high parasitemia cases formed significantly larger rosettes with human erythrocytes than PkDBPαII of isolates from low parasitemia cases (18,000 ± 13,000 µm2 and 1,315 ± 623 µm2, respectively).
Financial support: This study was supported by the Long-Term Research Grant Scheme (LRGS 1/2018) of the Ministry of Education Malaysia. The grant was awarded to M. Y. F., the University of Malaya (Grant number LR002A-2018).
Authors’ addresses: Fatma Diyana Mohd Bukhari, Yee Ling Lau, and Mun Yik Fong, Department of Parasitology, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia, E-mails: fatma_diyana@yahoo.com, lauyeeling@um.edu.my, and fongmy@um.edu.my.