The CD14+CD16+ Inflammatory Monocyte Subset Displays Increased Mitochondrial Activity and Effector Function During Acute Plasmodium vivax Malaria

et al. (2014) The CD14+CD16+ Inflammatory Monocyte Subset Displays Increased Mitochondrial Activity and Effector Function During Acute Plasmodium vivax Malaria. PLoS Pathog 10(9): e1004393. doi:10.1371/journal.ppat.1004393 + + The CD14 CD16 Inflammatory Monocyte Subset Displays Increased Mitochondrial Activity and Effector Function During Acute Plasmodium vivax Malaria Lis R. V. Antonelli 0 Fabiana M. S. Leoratti 0 Pedro A. C. Costa 0 Bruno C. Rocha 0 Suelen Q. Diniz 0 Mauro S. Tada 0 Dhelio B. Pereira 0 Andrea Teixeira-Carvalho 0 Douglas T. Golenbock 0 Ricardo Gonc alves 0 Ricardo T. Gazzinelli 0 Mary M. Stevenson, McGill University, Canada 0 1 Laborato rio de Immunopatologia, Centro de Pesquisas Rene Rachou, Fundac a o Oswaldo Cruz, Belo Horizonte, Minas Gerais, Brazil, 2 Departamento de Bioqu mica e Imunologia, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil, 3 Centro de Pesquisas em Medicina Tropical de Rondo nia, Porto Velho, Rondo nia, Brazil, 4 Laborato rio de Biomarcadores de Diagno stico e Monitorac a o, Centro de Pesquisas Rene Rachou, Fundac a o Oswaldo Cruz, Belo Horizonte, Minas Gerais, Brazil, 5 Division of Infectious Diseases and Immunology, University of Massachusetts Medical School , Worcester , Massachusetts, United States of America, 6 Departamento de Patologia Geral, Universidade Federal de Minas Gerais , Belo Horizonte, Minas Gerais , Brazil Infection with Plasmodium vivax results in strong activation of monocytes, which are important components of both the systemic inflammatory response and parasite control. The overall goal of this study was to define the role of monocytes during P. vivax malaria. Here, we demonstrate that P. vivax-infected patients display significant increase in circulating monocytes, which were defined as CD14+CD162 (classical), CD14+CD16+ (inflammatory), and CD14loCD16+ (patrolling) cells. While the classical and inflammatory monocytes were found to be the primary source of pro-inflammatory cytokines, the CD16+ cells, in particular the CD14+CD16+ monocytes, expressed the highest levels of activation markers, which included chemokine receptors and adhesion molecules. Morphologically, CD14+ were distinguished from CD14lo monocytes by displaying larger and more active mitochondria. CD14+CD16+ monocytes were more efficient in phagocytizing P. vivaxinfected reticulocytes, which induced them to produce high levels of intracellular TNF-a and reactive oxygen species. Importantly, antibodies specific for ICAM-1, PECAM-1 or LFA-1 efficiently blocked the phagocytosis of infected reticulocytes by monocytes. Hence, our results provide key information on the mechanism by which CD14+CD16+ cells control parasite burden, supporting the hypothesis that they play a role in resistance to P. vivax infection. - Funding: We acknowledge the Program for Technological Development in Tools for HealthPDTIS-FIOCRUZ for the use of its facilities. This work was supported by FAPEMIG (01/2011), CNPq (14/2011), PAPES VI, FIOCRUZ, the US National Institutes of Health (AI079293), by National Institute of Science and Technology for Vaccines (CNPq-573547/2008-4/FAPEMIG/MS-CBB-APQ 00077-09) and Rede Malaria (CNPq-555646/2009-2/FAPEMIG/MS-CBB-APQ-01153-10). RTG is a recipient of a Visiting Professor Fellowship from CAPES and the David Rockefeller Center for Latin American Studies at the Harvard School of Public Health. LRVA, ATC and RTG are CNPq fellows (PQ) and DTG is a FAPEMIG fellow. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. Plasmodium vivax is the most widely distributed malaria parasite and responsible for approximately 7080 million cases, annually. In addition, P. vivax is responsible for the majority of malaria cases and represents a significant impediment to social and economic development in Latin America and Asia [1]. Both innate and acquired immunity are thought to play critical role in host resistance to infection and pathogenesis of malaria [2,3]. However, the mechanisms by which the innate immune response mediate resistance to Plasmodium infection or promote a deleterious systemic inflammation associated with malaria sepsis are poorly understood [2]. This is particularly true in the case of P. vivax malaria [4]. The blood is the main tissue affected during P. vivax malaria since sequestration is not a central event in this infection. When parasitized reticulocytes rupture in the blood stream, parasite components are sensed by the innate immune receptors and activate monocytes [5]. The innate immune system recognizes Plasmodium sp. through different pattern-recognition receptors expressed by monocytes and initiates a broad spectrum of defense mechanisms [6,7,8,9,10]. Importantly, the same immune mediators involved in host resistance, such as pro-inflammatory cytokines are also thought to mediate pathology during acute malaria episodes [8,11,12]. However, the full spectrum of monocyte subsets and the specific functions of each monocyte population during malaria have not been defined. Besides supplying peripheral tissues with macrophage and dendritic cell (DC) precursors, monocytes contribute directly to immune defense against microbial pathogens [13,14,15]. Monocytes were initially identified by their expression of large amounts of CD14 [16,17]. However, recent studies have revealed that monocytes in human peripheral blood are heterogeneous and can be divided into three distinct subsets described based on their Malaria, caused by a protozoa parasite, Plasmodium, affects more than 200 million people per year. The infection triggers an acute febrile illness, the paroxysms, occurring every 48 or 72 hours depending on the species. Plasmodium vivax, in most cases, does not cause severe malaria, but it is the most geographically widespread parasite responsible for human disease and causes substantial costs to individuals and governments. Once the parasite reaches the blood stream, they infect reticulocytes that can be destroyed by phagocytes. Our goal was to assess the importance of monocyte subsets during malaria. We found that P. vivax infection causes an increase in frequency of circulating monocytes, which were defined as classical, inflammatory, and patrolling, based on the expression of membrane molecules. Classical and inflammatory monocytes produced higher levels of pro-inflammatory cytokines and were distinguished from patrolling monocytes by displaying larger and more active mitochondria. Importantly, inflammatory monocytes were more efficient phagocytes; produced high levels of intracellular reactive oxygen species and TNF and consequently control better Plasmodium vivax infection. Hence, our results support the hypothesis that CD14+CD16+ monocytes display effector functions involved in parasite control during malaria. expression of phenotypic (...truncated)