Mem Inst Oswaldo Cruz, Rio de Janeiro, VOLUME 114 | SEPTEMBER 2019
A simple, ex vivo phagocytosis assay of Plasmodium vivax merozoites by flow cytometry
1Universidade Federal do Amazonas, Manaus, Amazonas, Brazil
2Instituto Leônidas e Maria Deane (Fiocruz Amazônia), Manaus, Amazonas, Brazil
3Fundação de Medicina Tropical Dr. Heitor Vieira Dourado, Manaus, Amazonas, Brazil
As phagocytosis is the first line of defense against malaria, we developed a phagocytosis assay with Plasmodium vivax (P. vivax) merozoites that can be applied to evaluate vaccine candidates. Briefly, after leukocyte removal with loosely packed cellulose powder in a syringe, P. vivax trophozoites matured to the merozoite-rich schizont stages in the presence of the E64 protease inhibitor. The Percoll gradient-enriched schizonts were chemically disrupted to release merozoites that were submitted to merozoite opsonin-dependent phagocytosis in two phagocytic lines with human and mouse antibodies against the N- and C-terminal domains of P. vivax Merozoite Surface Protein-1. The resulting assay is simple and efficient for use as a routine phagocytic assay for the evaluation of merozoite stage vaccine candidates.