Duffy-Positive Reticulocytes Generated In Vitro from Human Peripheral Blood CD34 Haematopoietic Stem Cells Are Susceptible To Invasion by Plasmodium knowlesi

Plasmodium knowlesi shows a predilection towards human reticulocytes that have the Duffy blood group antigens required for malaria parasite invasion. Low concentration of reticulocytes obtained from peripheral blood restricts the use of these cells for P. knowlesi in vitro culture. Therefore, the present study aimed to generate reticulocytes in vitro from human peripheral blood CD34 haematopoietic stem cells (PB-derived CD34 HSCs) and determine the presence of the Duffy blood group antigens on generated reticulocytes before invasion with P. knowlesi. Following expansion and differentiation of PB-derived CD34 HSCs to reticulocytes, the Duffy blood group of generated reticulocytes was determined by using a polymerase chain reaction-sequence specific primer (PCR-SSP) before inoculation with the malaria parasite. Results show that the generated reticulocytes had FY*A/FY*B genotype indicated by the amplification bands at 720 bp. These Duffy-positive reticulocytes as enucleated cells on day 14 of differentiation were also invaded by the malaria parasite. This study demonstrates the susceptibility of the reticulocytes generated from the HSCs with the Fy(a+b+) phenotype for P. knowlesi invasion, which may lead to the establishment of in vitro culture and research of this malaria parasite.