Total Leukocyte Count in Rattus norvegicus after Duffy Binding‑Like 2β‑Plasmodium falciparum Erythrocyte Membrane Protein 1 Recombinant Protein Injection: The way to a Peptide‑based Malaria Vaccine Development

Abstract

Introduction: Severe malaria caused by Plasmodium falciparum is mediated by the P. falciparum erythrocyte membrane protein 1 (PfEMP1). It has a DBL2β domain that specifically binds to the intercellular adhesion molecule-1 (ICAM-1) receptor that lies in endothelial cells of many vital organs and is involved in malaria pathogenesis. Antibody against the DBL2β-PfEMP1 protein correlates with a reduced risk of severe malaria, making it a potential malaria vaccine candidate. This study aimed to examine total leukocytes after serial DBL2β-PfEMP1 recombinant protein injection to determine its immunogenicity. Settings and Design: This was an experimental study using pre-post control groups design. Methods: Samples were male rats aged 2-3 months with a weight of 150-350 g. Rats were injected 3x with 100 µg, 150 µg, and 200 µg of the purified DBL2β-PfEMP1 recombinant protein in the three-weeks interval. Blood samples were collected on days 0, 8, 29, and 50, and total leukocytes were counted using the improved Neubauer counting chamber and observed under a microscope. The data were analyzed using the Friedman test, Kruskal Wallis test, and Mann-Whitney test. Results: The lowest leukocyte level was at the pre-injection, and the highest level was after the third injection. There was a significant increase in leukocytes (P < 0.05) in all treatment groups but no increase in the control group. A dose of 100 µg of DBL2β-PfEMP1 recombinant protein showed the best response in inducing the increase of total leukocytes. Conclusion: The DBL2β-PfEMP1 recombinant protein could induce the higher leukocyte level in each injection, especially after the third injection.