Method, Retiply, for Producing Human Reticulocytes in Large Numbers for Sustainment of Continuous Culture of P. vivax

Plasmodium vivax malaria is an important factor of morbidity in many regions of Asia and Latin America. Culturing P. vivax has been difficult because of stringent requirements for reticulocytes as target cells. To address the Army"s need for a method of producing large numbers of reticulocytes on a regular basis, Physical Optics Corporation (POC) proposes to develop a new method, Retiply, for producing human reticulocytes in large numbers to sustain continuous cultures of P. vivax. The method is based on expansion and differentiation of human stem cells to produce reticulocytes, followed by storage until use. The innovation in the integration of reagents and protocols for passaging the cells to induce expansion and differentiation into reticulocytes enables Retiply to produce reticulocytes in high numbers. As a result, Retiply provides competent cells for invasion and sustainment of P. vivax. In Phase I, POC will develop the media and culture conditions and demonstrate the feasibility of producing log9-log10 reticulocytes with hemoglobin>50%. In Phase II, production efficiency will be further enhanced with reticulocyte content of>60% and>50% of reticulocytes as Duffy+. Additionally, the ability of the prepared cells to sustain P. vivax invasion will be investigated at WRAIR.