Hillyer Lab News
Hillyer Lab News
Article on the interaction between the mosquito circulatory and immune systems is Published In PLoS Pathogens
Thursday, November 29, 2012
An article detailing the physiological interaction between the mosquito circulatory and immune systems in response to infection was published today in the journal PLoS Pathogens. In this study we performed mosquito intravital imaging and organismal manipulations to show, among other things, that:
1. There are two types of endocytic cells that flank the mosquito heart: pericardial cells and periostial hemocytes.
2.Periostial hemocytes engage in the phagocytosis of pathogens at the location of the heart ostia (valves).
3.Hemocytes aggregate in the periostial regions in response to bacterial and malaria infection, and this aggregation occurs in a time- and dose-dependent manner.
4.This study comprehensively describes an insect immune response that fundamentally relies on the physiological interaction between the circulatory and immune systems.
Article Citation:
King, J.G., and J.F. Hillyer. 2012. Infection-induced interaction between the mosquito circulatory and immune systems. PLoS Pathogens. 8(11): e1003058. (Pubmed) (Download Free from PLoS Pathogens)
This article is featured on the cover of the November issue of PLoS Pathogens:
Left image: The study’s authors were Julián Hillyer (left) and Jonas King (right).
Right image:Mosquito heart (green tube-like structure extending left to right) and periostial hemocytes (red).
Author summary:
Mosquitoes transmit diseases such as malaria, dengue fever, west nile virus and lymphatic filariasis. A mosquito initially acquires a pathogen when she ingests a blood meal from an infected person or animal. Then, after a period of development and/or replication in the mosquito gut, the pathogen enters the hemocoel (body cavity) and undergoes an obligate migration to the salivary glands (the destination for viruses and protozoans) or the mouthparts (the destination for larger worms). During this migration, pathogens are subject to two potentially antagonistic mosquito forces: immune responses and circulatory currents. In this study, we examined the physiological interactions between the mosquito immune and circulatory systems. We show that when mosquitoes are infected with bacteria or malaria parasites, mosquito immune cells (hemocytes) migrate to the areas surrounding the valves of the heart. At these areas of rapid and dynamic hemolymph (mosquito blood) flow, hemocytes swiftly phagocytose and kill pathogens. These experiments describe a novel and basal insect immune response that fundamentally relies on the physiological interaction between the mosquito circulatory and immune system. Furthermore, because traversal of the hemocoel is required for pathogen transmission, this new knowledge could be used in the development of novel disease control strategies.
Diagram of the mosquito heart, including the periostial regions.
Article abstract:
Insects counter infection with innate immune responses that rely on cells called hemocytes. Hemocytes exist in association with the insect’s open circulatory system and this mode of existence has likely influenced the organization and control of anti-pathogen immune responses. Previous studies reported that pathogens in the mosquito body cavity (hemocoel) accumulate on the surface of the heart. Using novel cell staining, microdissection and intravital imaging techniques, we investigated the mechanism of pathogen accumulation in the pericardium of the malaria mosquito, Anopheles gambiae, and discovered a novel insect immune tissue, herein named periostial hemocytes, that sequesters pathogens as they flow with the hemolymph. Specifically, we show that there are two types of endocytic cells that flank the heart: periostial hemocytes and pericardial cells. Resident periostial hemocytes engage in the rapid phagocytosis of pathogens, and during the course of a bacterial or Plasmodium infection, circulating hemocytes migrate to the periostial regions where they bind the cardiac musculature and each other, and continue the phagocytosis of invaders. Periostial hemocyte aggregation occurs in a time- and infection dose-dependent manner, and once this immune process is triggered, the number of periostial hemocytes remains elevated for the lifetime of the mosquito. Finally, the soluble immune elicitors peptidoglycan and β-1,3-glucan also induce periostial hemocyte aggregation, indicating that this is a generalized and basal immune response that is induced by diverse immune stimuli. These data describe a novel insect cellular immune response that fundamentally relies on the physiological interaction between the insect circulatory and immune systems.
Update (December, 2012): PLoS Pathogens changed their web design. Below is the new look of the cover of the November 2012 issue:
“PLOS Pathogens is an open-access journal that publishes important new ideas on bacteria, fungi, parasites, prions, and viruses that contribute to our understanding of the biology of pathogens and pathogen-host interactions.”