Humoral immunity prevents clinical malaria during Plasmodium relapses without eliminating gametocytes

• Published in: PLoS pathogens Vol. 15; no. 9; p. e1007974
• Main Authors: Joyner, Chester J, Brito, Cristiana F A, Saney, Celia L, Joice Cordy, Regina, Smith, Maren L, Lapp, Stacey A, Cabrera-Mora, Monica, Kyu, Shuya, Lackman, Nicolas, Nural, Mustafa V, DeBarry, Jeremy D, Kissinger, Jessica C, Styczynski, Mark P, Lee, F Eun-Hyung, Lamb, Tracey J, Galinski, Mary R
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 19-09-2019; Public Library of Science (PLoS)
• Subjects: Anemia; Animals; Antibodies, Protozoan - blood; B cells; B-Lymphocytes - immunology; Behavior; Bioinformatics; Biology and Life Sciences; Blood; Consortia; Critical care; Development and progression; Disease transmission; Flow cytometry; Funding; Gametocytes; Gene Expression Profiling; Gene sequencing; Health aspects; Homology; Host-Parasite Interactions - genetics; Host-Parasite Interactions - immunology; Humans; Humoral immunity; Immunity; Immunity (Physiology); Immunity, Humoral - genetics; Immunoglobulin G; Immunoglobulin G - blood; Immunoglobulins; Immunologic Memory - genetics; Immunological memory; Immunology; Infection; Infections; Inflammation; Liver; Lymphocytes B; Macaca mulatta; Malaria; Malaria - genetics; Malaria - immunology; Malaria - parasitology; Malaria, Vivax - genetics; Malaria, Vivax - immunology; Malaria, Vivax - parasitology; Male; Medical research; Medicine; Medicine and Health Sciences; Memory cells; Monkeys & apes; Parasitemia; Parasitemia - genetics; Parasitemia - immunology; Parasitemia - parasitology; Parasites; Pathogens; Phagocytosis; Plasmodium; Plasmodium (Protozoa); Plasmodium cynomolgi - immunology; Plasmodium cynomolgi - pathogenicity; Plasmodium vivax - immunology; Plasmodium vivax - pathogenicity; Prevention; Recurrence; Recurrence (Disease); Reduction; Ribonucleic acid; RNA; Sleep; Software; Sporozoites - immunology; Sporozoites - pathogenicity; Supervision; Tropical diseases; Vector-borne diseases; United States; Atlanta Georgia; United States > US; Georgia
• ISSN: 1553-7374; 1553-7366; 1553-7374
• DOI: 10.1371/journal.ppat.1007974

Plasmodium relapses are attributed to the activation of dormant liver-stage parasites and are responsible for a significant number of recurring malaria blood-stage infections. While characteristic of human infections caused by P. vivax and P. ovale, their relative contribution to malaria disease burden and transmission remains poorly understood. This is largely because it is difficult to identify 'bona fide' relapse infections due to ongoing transmission in most endemic areas. Here, we use the P. cynomolgi-rhesus macaque model of relapsing malaria to demonstrate that clinical immunity can form after a single sporozoite-initiated blood-stage infection and prevent illness during relapses and homologous reinfections. By integrating data from whole blood RNA-sequencing, flow cytometry, P. cynomolgi-specific ELISAs, and opsonic phagocytosis assays, we demonstrate that this immunity is associated with a rapid recall response by memory B cells that expand and produce anti-parasite IgG1 that can mediate parasite clearance of relapsing parasites. The reduction in parasitemia during relapses was mirrored by a reduction in the total number of circulating gametocytes, but importantly, the cumulative proportion of gametocytes increased during relapses. Overall, this study reveals that P. cynomolgi relapse infections can be clinically silent in macaques due to rapid memory B cell responses that help to clear asexual-stage parasites but still carry gametocytes.