Antibody-Dependent THP-1 Cell-Mediated Phagocytosis of Plasmodium falciparum-Infected Erythrocytes.

Antibodies that recognize variant surface antigens (VSAs) expressed on Plasmodium falciparum-infected erythrocytes (IEs) opsonize IEs for phagocytic clearance. The anti-VSA antibodies promote antibody-dependent cellular phagocytosis (ADCP) of IEs by interacting with innate immune cells. ADCP is an important immune effector mechanism of parasite clearance. ADCP can be a tool to assess the efficacy of vaccine-induced antibodies, in addition to measuring the neutralizing ability of antibodies. Here, we developed and validated an efficient and high-throughput plate-based flow cytometric assay to measure ADCP of IEs using the human monocytic THP-1 cell line. This flow cytometric assay can be used to analyze the level of naturally acquired or vaccine-induced opsonic antibodies in large cohorts.